SEC Filing - Spectrum Pharmaceuticals, Inc.

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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE
SECURITIES EXCHANGE ACT OF 1934 (AMENDMENT NO. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant □

Check the appropriate box:

□

Preliminary Proxy Statement

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Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under § 240 14a-12

SPECTRUM PHARMACEUTICALS, INC.

(Name of Registrant as Specified In Its Charter)

N/A

(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

□

No fee required

☒

Fee paid previously with preliminary materials

□

Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11

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MERGER PROPOSAL — YOUR VOTE IS VERY IMPORTANT

Dear Assertio Holdings, Inc. Stockholders and Spectrum Pharmaceuticals, Inc. Stockholders:

On April 24, 2023, Assertio Holdings, Inc., which is referred to as “Assertio,” Spade Merger Sub 1, Inc., a wholly owned subsidiary of Assertio, which is referred to as “Merger Sub” and Spectrum Pharmaceuticals, Inc., which is referred to as “Spectrum,” entered into an Agreement and Plan of Merger, as it may be amended from time to time, which is referred to as the “Merger Agreement,” that provides for the acquisition of Spectrum by Assertio. Upon the terms and subject to the conditions of the Merger Agreement, Assertio will acquire Spectrum through a merger of Merger Sub with and into Spectrum, with Spectrum continuing as the surviving corporation and becoming a wholly owned subsidiary of Assertio. The combined company will continue to be named Assertio Holdings, Inc.

Upon the successful completion of the merger, each issued and outstanding share of common stock, par value $0.001 per share, of Spectrum, which is referred to as “Spectrum common stock” (other than treasury shares, shares held by Assertio or Merger Sub and shares of Spectrum common stock held by any holder who is entitled to demand and properly demands appraisal of such shares in compliance with Section 262 of the Delaware General Corporation Law) will be converted into the right to receive (i) 0.1783 shares of common stock, par value $0.0001 per share, of Assertio, which is referred to as “Assertio common stock,” which number is referred to as the “exchange ratio,” with cash (without interest and less any applicable withholding taxes) being paid in lieu of any fractional shares of Assertio common stock that Spectrum stockholders would otherwise be entitled to receive, which shares of Assertio common stock and cash payment is referred to as the “Upfront Merger Consideration,” and (ii) one non-tradeable contingent value right, which is referred to as a “CVR,” for each share of Spectrum common stock you own. Each CVR will represent a contractual right to receive future conditional payments worth up to an aggregate maximum amount of $0.20, settleable in cash, additional shares of Assertio common stock or a combination of cash and additional shares of Assertio common stock, at Assertio’s sole discretion, upon the achievement of certain sales milestones related to Spectrum’s product ROLVEDON. The minimum payment on each CVR is zero and the maximum payment is $0.20. Assertio stockholders will continue to own their existing shares of Assertio common stock.

The exchange ratio is fixed and will not be adjusted for changes in the market price of either Assertio common stock or Spectrum common stock between the date of signing of the Merger Agreement and the completion date of the merger. Based on the number of shares of Assertio common stock and Spectrum common stock outstanding on June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, it is expected that Assertio will issue approximately 36.6 million shares of Assertio common stock in the merger (without consideration of the shares of Assertio common stock underlying the CVRs) and, upon completion of the merger, former Spectrum stockholders are expected to own approximately 35% of the outstanding shares of Assertio common stock and Assertio stockholders immediately prior to the merger are expected to own approximately 65% of the outstanding shares of Assertio common stock. Assertio common stock is traded on The Nasdaq Stock Market LLC, which is referred to as “Nasdaq SM,” under the symbol “ASRT.” Spectrum common stock is traded on the Nasdaq Capital Market, which is referred to as “Nasdaq CM,” under the symbol “SPPI.” We encourage you to obtain current quotes for both the Assertio and Spectrum common stock before voting at the special meetings of stockholders described below.

Because the exchange ratio is fixed, the market value of the Upfront Merger Consideration to Spectrum stockholders will fluctuate with the market price of the Assertio common stock and will not be known at the time that Spectrum stockholders vote on the merger. On June 14, 2023, the latest practicable trading day before the date of the filing of this joint proxy statement/prospectus, the closing price of Assertio common stock on the Nasdaq SM was $6.03 per share, resulting in an implied value of the Upfront Merger Consideration to Spectrum stockholders of $1.08 per share of Spectrum common stock.

Assertio and Spectrum will each hold special meetings of their respective stockholders to vote on the proposals necessary to complete the merger. Such special meetings are referred to as the “Assertio special meeting” and the “Spectrum special meeting,” respectively.

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At the Assertio special meeting, Assertio stockholders will be asked to consider and vote on (i) a proposal to approve the issuance of shares of Assertio common stock to Spectrum stockholders in connection with the merger (including such shares issued as payment under the CVRs), which proposal is referred to as the “Assertio share issuance proposal,” and (ii) a proposal to adjourn the Assertio special meeting to solicit additional proxies if there are insufficient votes to approve the Assertio share issuance proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Assertio stockholders. The Assertio board of directors unanimously recommends that Assertio stockholders vote “FOR” each of the proposals to be considered at the Assertio special meeting.

At the Spectrum special meeting, Spectrum stockholders will be asked to consider and vote on (i) a proposal to adopt the Merger Agreement, which proposal is referred to as the “Spectrum merger proposal,” (ii) a proposal to approve, on a non-binding advisory basis, the compensation that may be paid or become payable to Spectrum named executive officers that is based on or otherwise relates to the transactions contemplated by the Merger Agreement and (iii) a proposal to adjourn the Spectrum special meeting to solicit additional proxies, if necessary or appropriate, if there are insufficient votes to approve the Spectrum merger proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Spectrum stockholders. The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” each of the proposals to be considered at the Spectrum special meeting.

We cannot complete the merger unless the Assertio share issuance proposal is approved by Assertio stockholders and the Spectrum merger proposal is approved by Spectrum stockholders. Your vote on these matters is very important, regardless of the number of shares you own. Whether or not you plan to virtually attend your company’s respective special meeting, please vote by proxy over the internet or telephone using the instructions included with the accompanying proxy card, or promptly complete your proxy card and return it in the enclosed postage-paid envelope, in order to authorize the individuals named on your proxy card to vote your shares at the applicable special meeting.

This joint proxy statement/prospectus provides you with important information about the special meetings, the merger and each of the proposals. We encourage you to read the entire document carefully, in particular the information under “Risk Factors” beginning on page 36 for a discussion of risks relevant to the merger.

We look forward to the successful completion of the merger.

Sincerely,

Daniel A. Peisert
President and Chief Executive Officer
Assertio Holdings, Inc.

Thomas J. Riga
President and Chief Executive Officer
Spectrum Pharmaceuticals, Inc.

* * * * *

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of the merger, the adoption of the Merger Agreement, the Assertio common stock and the CVRs to be issued in the merger or any of the other transactions described in this joint proxy statement/prospectus or determined if this joint proxy statement/prospectus is accurate or complete. Any representation to the contrary is a criminal offense.

This joint proxy statement/prospectus is dated as of, and is first being mailed to Assertio and Spectrum stockholders on or about, June 15, 2023.

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Assertio Holdings, Inc.
100 South Saunders Road, Suite 300
Lake Forest, Illinois 60045
(224) 419-7106

NOTICE OF SPECIAL MEETING OF STOCKHOLDERS
TO BE HELD ON JULY 27, 2023

To the Stockholders of Assertio Holdings, Inc.:

Notice is hereby given that Assertio Holdings, Inc., which is referred to as “Assertio,” will hold a special meeting of its stockholders, which is referred to as the “Assertio special meeting,” virtually via live webcast on July 27, 2023, beginning at 12:30 p.m., Central Time. You will be able to virtually attend and vote at the Assertio special meeting by visiting www.cstproxy.com/assertiotx/sm2023, which is referred to as the “Assertio special meeting website.”

The Assertio special meeting will be held for the purpose of Assertio stockholders considering and voting on the following proposals:

1. to approve the issuance of shares of Assertio common stock to the stockholders of Spectrum Pharmaceuticals, Inc., which is referred to as “Spectrum,” in connection with the merger contemplated by the Agreement and Plan of Merger, dated April 24, 2023, as it may be amended from time to time, which is referred to as the “Merger Agreement,” by and among Assertio, Spade Merger Sub 1, Inc., a wholly owned subsidiary of Assertio, and Spectrum, including the issuance of shares of Assertio common stock as payments under the contingent value rights, which are referred to as CVRs, issued in connection with such merger, which issuances are referred to as the “share issuance” and which proposal is referred to as the “Assertio share issuance proposal”; and

2. to approve the adjournment of the Assertio special meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Assertio special meeting to approve the Assertio share issuance proposal or to ensure that any supplement or amendment to the accompanying joint proxy statement/prospectus is timely provided to Assertio stockholders, which proposal is referred to as the “Assertio adjournment proposal.”

Assertio will transact no other business at the Assertio special meeting except such business as may properly be brought before the Assertio special meeting or any adjournment or postponement thereof. The accompanying joint proxy statement/prospectus, including the Merger Agreement attached as Annex A thereto, contains further information relating to these matters.

Only holders of record of Assertio common stock at the close of business on June 13, 2023, the record date for voting at the Assertio special meeting, are entitled to notice of and to vote at the Assertio special meeting and any adjournments or postponements thereof.

The Assertio board of directors has unanimously determined that the terms of the Merger Agreement and the merger are fair to and in the best interests of Assertio and its stockholders, and has approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the merger and the share issuance. Accordingly, the Assertio board of directors unanimously recommends that Assertio stockholders vote:

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“FOR” the Assertio share issuance proposal; and

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“FOR” the Assertio adjournment proposal.

Your vote is very important, regardless of the number of shares of Assertio common stock you own. The parties cannot complete the merger unless the Assertio share issuance proposal is approved by Assertio stockholders. Assuming a quorum is present at the Assertio special meeting, approval of the Assertio share

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issuance proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal.

Your vote is important. Whether or not you plan to virtually attend the Assertio special meeting, please vote by proxy over the internet or telephone using the instructions included with the accompanying proxy card, or promptly complete your proxy card and return it in the enclosed postage-paid envelope, in order to authorize the individuals named on your proxy card to vote your shares of Assertio common stock at the Assertio special meeting. If you hold your shares through a broker, bank or other nominee in “street name” (instead of as a registered holder) please follow the instructions on the voting instruction form provided by your bank, broker or nominee to vote your shares. The list of Assertio stockholders entitled to vote at the Assertio special meeting will be available at Assertio’s headquarters during regular business hours for examination by any Assertio stockholder for any purpose germane to the Assertio special meeting for a period of at least ten days prior to the Assertio special meeting.

If you have any questions about the merger, please contact Assertio at (224) 419-7106 or write to Assertio Holdings, Inc., by emailing Assertio at corpgov@assertiotx.com.

If you have any questions about how to vote or direct a vote in respect of your shares of Assertio common stock, please contact Assertio’s proxy solicitor, Alliance Advisors, LLC, at ASRT@allianceadvisors.com or (833) 757-0785. Banks and brokers may call (973) 518-3365.

By Order of the Board of Directors,

Daniel A. Peisert
President and Chief Executive Officer
Assertio Holdings, Inc.

Lake Forest, Illinois
Dated: June 15, 2023

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NOTICE OF SPECIAL MEETING OF STOCKHOLDERS
OF SPECTRUM PHARMACEUTICALS, INC.
To be held, July 27, 2023

To the Stockholders of Spectrum Pharmaceuticals, Inc.,

Notice is hereby given that the special meeting of stockholders (the “Spectrum special meeting”) of Spectrum Pharmaceuticals, Inc. (“Spectrum”) will be held virtually on July 27, 2023 at 10:00 a.m., Eastern Time at www.meetnow.global/MYXFZTA. The Spectrum special meeting will be held for the following purposes:

Agreement and Plan of Merger. To vote on a proposal to adopt the Agreement and Plan of Merger (as it may be amended from time to time, the “Merger Agreement”), a copy of which is attached as Annex A to the enclosed joint proxy statement/prospectus (the “Spectrum merger proposal”);

Advisory Vote on Compensation of Spectrum’s Named Executive Officers. To vote on a proposal to approve, on an advisory (non-binding) basis, the compensation that will or may be paid to Spectrum’s named executive officers in connection with the Merger (as defined below) (the “Spectrum advisory compensation proposal”); and

Adjournment. To vote on a proposal to approve the adjournment of the Spectrum special meeting to solicit additional proxies if there are not sufficient votes cast at the Spectrum special meeting to approve the Spectrum merger proposal or to ensure that any supplemental or amended disclosure, including any supplement or amendment to the enclosed joint proxy statement/prospectus, is timely provided to Spectrum stockholders (the “Spectrum adjournment proposal”).

Spectrum will transact no other business at the Spectrum special meeting or any adjournment or postponement thereof, except such business as may properly be brought before the Spectrum special meeting or any adjournment or postponement thereof in accordance with the Fourth Amended and Restated Bylaws of Spectrum (the “Spectrum bylaws”). The enclosed joint proxy statement/prospectus, of which this notice is a part, describes the proposals listed above in more detail. Please refer to the attached documents, including the Merger Agreement and all other annexes and any documents incorporated by reference, for further information with respect to the business to be transacted at the Spectrum special meeting. You are encouraged to read the entire document carefully before voting. In particular, please see the sections titled “The Merger” beginning on page 71 of the enclosed joint proxy statement/prospectus for a description of the transactions contemplated by the Merger Agreement and “Risk Factors” beginning on page 36 of the enclosed joint proxy statement/prospectus for an explanation of the risks associated with the merger and the other transactions contemplated by the Merger Agreement.

If a quorum is present at the Spectrum special meeting, approval of the Spectrum merger proposal by the affirmative vote of the holders of a majority of the outstanding shares of Spectrum common stock, par value $0.001 per share (“Spectrum common stock”), entitled to vote on the proposal is required to consummate the merger of Merger Sub with and into Spectrum, with Spectrum surviving the merger as a direct, wholly owned subsidiary of Assertio, as contemplated by the Merger Agreement (the “Merger”). Holders of Spectrum common stock (“Spectrum stockholders”) will also be asked to approve the Spectrum advisory compensation proposal and the Spectrum adjournment proposal. If a quorum is present at the Spectrum special meeting, approval of the Spectrum advisory compensation proposal and the Spectrum adjournment proposal each requires the affirmative vote of the holders of a majority of the outstanding shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting. The chairperson of the meeting will have the right and authority to recess and/or adjourn the Spectrum special meeting and, if a quorum is not present at the Spectrum special meeting,

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Spectrum stockholders holding a majority in voting power of shares of Spectrum capital stock, present in person or by proxy and entitled to vote thereat, will have the power to adjourn the meeting (subject to certain restrictions in the Merger Agreement, including that adjournment, without Assertio’s consent, must be more than five but less than 20 days after the date on which the Spectrum special meeting was originally scheduled). For additional information regarding the conduct of the Spectrum special meeting, please see the section titled “The Spectrum Special Meeting” beginning on page 60 of the enclosed joint proxy statement/prospectus.

The Spectrum board of directors (the “Spectrum board of directors”) has fixed the close of business on June 13, 2023, as the record date (the “Spectrum record date”) for the determination of the Spectrum stockholders entitled to receive notice of, and to vote at, the Spectrum special meeting or any adjournment or postponement thereof. The Spectrum stockholders of record as of the close of business on the Spectrum record date are the only Spectrum stockholders who are entitled to receive notice of, and to vote at, the Spectrum special meeting and any adjournment or postponement thereof unless a new record date is fixed in connection with any adjournment or postponement of the Spectrum special meeting. Each Spectrum stockholder has one vote for each share of Spectrum common stock held as of the Spectrum record date. A list of Spectrum’s stockholders of record entitled to vote at the Spectrum special meeting will be available for examination by any Spectrum stockholder for any legally valid purpose at Spectrum’s corporate headquarters, located at 2 Atlantic Avenue, 6th Floor, Boston, MA 02110, for a period of ten days prior to the Spectrum special meeting. The list of eligible Spectrum stockholders of record also will be available for inspection during the Spectrum special meeting at www.meetnow.global/MYXFZTA by entering the 15-digit control number provided on your proxy card or voting instruction form and completing the required online attestation form. For additional information regarding the Spectrum special meeting, see the section titled “The Spectrum Special Meeting” beginning on page 60 of the enclosed joint proxy statement/prospectus.

The Spectrum board of directors, at a meeting duly called and held, has (i) determined that the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement are fair and in the best interest of, and are advisable to, Spectrum and the Spectrum stockholders, (ii) approved and adopted the Merger Agreement and approved the Merger and the other transactions contemplated by the Merger Agreement and (iii) recommended that the Spectrum stockholders approve the Merger Agreement. The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal.

Properly executed proxy cards with no instructions indicated on the proxy card will be voted “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal. Even if you plan to attend the Spectrum special meeting, Spectrum requests that you complete, sign, date and return the enclosed proxy card in the accompanying envelope prior to the Spectrum special meeting to ensure that your shares will be represented and voted at the Spectrum special meeting if you later decide not to or are unable to attend.

You may also submit a proxy over the Internet using the Internet address on the enclosed proxy card or by telephone using the toll-free number on the enclosed proxy card. If you submit your proxy through the Internet or by telephone, you will be asked to provide the control number from the enclosed proxy card. If you are not a stockholder of record, but instead hold your shares in “street name” through a broker, bank, trustee or other nominee, you must provide a proxy executed in your favor from your broker, bank, trustee or other nominee in order to be able to vote at the Spectrum special meeting.

Please vote as promptly as possible, whether or not you plan to attend the Spectrum special meeting. If your shares are held in the name of a broker, bank or other nominee, please vote by following the instructions on the voting instruction form furnished by the broker, bank or other nominee. If you hold your shares in your own name, submit a proxy to vote your shares as promptly as possible by (i) visiting the Internet site listed on the proxy card, (ii) calling the toll-free number listed on the proxy card or (iii) submitting your proxy card by mail by using the self-addressed, stamped envelope provided. Submitting a proxy will not prevent you from voting, but it will help to secure a quorum and avoid added solicitation costs. Any eligible Spectrum stockholder entitled to vote and who is virtually present at the Spectrum special meeting may vote, thereby revoking any previous proxy. In addition, a proxy may also be revoked in writing before the Spectrum special meeting in the manner described in the enclosed joint proxy statement/prospectus.

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The enclosed joint proxy statement/prospectus provides a detailed description of the Merger, the Merger Agreement and the other matters to be considered at the Spectrum special meeting. We urge you to read carefully the enclosed joint proxy statement/prospectus — including any documents incorporated by reference — and the annexes in their entirety. If you have any questions concerning the Spectrum merger proposal, the Spectrum advisory compensation proposal, the Spectrum adjournment proposal, the Merger or the enclosed joint proxy statement/prospectus, would like additional copies, or need help voting your shares of Spectrum common stock, please contact:

Innisfree M&A Incorporated

501 Madison Avenue, 20th Floor
New York, NY 10022
Stockholders May Call: (877) 800-5185 (toll-free from the U.S. and Canada)
Banks and Brokers May Call: (212) 750-5833

By Order of the Board of Directors
Keith McGahan
Executive Vice President, Chief Legal Officer and Corporate Secretary

June 15, 2023

WHETHER OR NOT YOU PLAN TO ATTEND THE SPECTRUM SPECIAL MEETING, YOU ARE URGED TO VOTE AS SOON AS POSSIBLE BY INTERNET, TELEPHONE OR MAIL SO THAT YOUR SHARES MAY BE VOTED IN ACCORDANCE WITH YOUR WISHES. SUBMITTING A PROXY DOES NOT AFFECT YOUR RIGHT TO REVOKE IT LATER OR VOTE YOUR SHARES IN PERSON IN THE EVENT YOU SHOULD ATTEND THE SPECTRUM SPECIAL MEETING.

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REFERENCES TO ADDITIONAL INFORMATION

This joint proxy statement/prospectus incorporates important business and financial information about Assertio and Spectrum from other documents that Assertio and Spectrum have filed with the SEC and that are not contained in and are instead incorporated by reference in this joint proxy statement/prospectus. For a list of documents incorporated by reference in this joint proxy statement/prospectus, see “Where You Can Find More Information.” This information is available for you, without charge, to review through the SEC’s website at www.sec.gov.

You may request a copy of this joint proxy statement/prospectus, any of the documents incorporated by reference in this joint proxy statement/prospectus or other information filed with the SEC by Assertio or Spectrum, without charge, by written or telephonic request directed to the appropriate company at the following contacts:

	For Assertio stockholders:			For Spectrum stockholders:
	Assertio Holdings, Inc. Attention: General Counsel corpgov@assertiotx.com. (224) 419-7106			Spectrum Pharmaceuticals, Inc. Attention: Investor Relations ir@sppirx.com (949) 788-6700

In order for you to receive timely delivery of the documents in advance of the special meeting of Assertio stockholders to be held on July 27, 2023, which is referred to as the “Assertio special meeting,” or the special meeting of Spectrum stockholders to be held on July 27, 2023, which is referred to as the “Spectrum special meeting,” as applicable, you must request the information no later than July 20, 2023.

If you have any questions about the Assertio special meeting or the Spectrum special meeting, or need to obtain proxy cards or other information, please contact the applicable company’s proxy solicitor at the following contacts:

	For Assertio stockholders:			For Spectrum stockholders:
	Alliance Advisors, LLC 200 Broadacres Drive, 3rd Floor Bloomfield, NY 07003 (973) 873-7700 www.allianceadvisors.com			Innisfree M&A Incorporated 501 Madison Avenue, 20th Floor New York, NY 10022 (877) 800-5185

The contents of the websites of the SEC, Assertio, Spectrum or any other entity are not incorporated in this joint proxy statement/prospectus. The information about how you can obtain certain documents that are incorporated by reference in this joint proxy statement/prospectus at these websites is being provided only for your convenience.

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ABOUT THIS JOINT PROXY STATEMENT/PROSPECTUS

This joint proxy statement/prospectus, which forms part of a registration statement on Form S-4 filed with the SEC by Assertio (Registration No. 333-272355), constitutes a prospectus of Assertio under Section 5 of the Securities Act with respect to the shares of Assertio common stock to be issued to Spectrum stockholders pursuant to the Agreement and Plan of Merger, dated April 24, 2023, as it may be amended from time to time, by and among Assertio, Merger Sub and Spectrum, which is referred to as the “Merger Agreement.” This document also constitutes a proxy statement of each of Assertio and Spectrum under Section 14(a) of the Exchange Act. This joint proxy statement/prospectus also constitutes a notice of meeting with respect to each of the Assertio and Spectrum special meetings.

Assertio has supplied all information contained or incorporated by reference in this joint proxy statement/prospectus relating to Assertio and Merger Sub, and Spectrum has supplied all such information relating to Spectrum. Assertio and Spectrum have both contributed to such information relating to the Merger.

You should rely only on the information contained or incorporated by reference in this joint proxy statement/prospectus. Assertio and Spectrum have not authorized anyone to provide you with information that is different from that contained or incorporated by reference in this joint proxy statement/prospectus. This joint proxy statement/prospectus is dated June 15, 2023, and you should not assume that the information contained in this joint proxy statement/prospectus is accurate as of any date other than such date unless otherwise specifically provided herein.

Further, you should not assume that the information incorporated by reference in this joint proxy statement/prospectus is accurate as of any date other than the date of the incorporated document. Neither the mailing of this joint proxy statement/prospectus to Assertio or Spectrum stockholders nor the issuance by Assertio of shares of Assertio common stock pursuant to the Merger Agreement will create any implication to the contrary.

This joint proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction.

Unless otherwise indicated or the context otherwise requires, when used in this joint proxy statement/prospectus:

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“Assertio” refers to Assertio Holdings, Inc., a Delaware corporation;

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“Assertio adjournment proposal” refers to the proposal to approve the adjournment of the Assertio special meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Assertio special meeting to approve the Assertio share issuance proposal or to ensure that any supplement or amendment to the accompanying joint proxy statement/prospectus is timely provided to Assertio stockholders;

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“Assertio board of directors” refers to the board of directors of Assertio;

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“Assertio bylaws” refers to the Amended and Restated Bylaws of Assertio, dated November 2, 2022, as amended;

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“Assertio charter” refers to the Amended and Restated Certificate of Incorporation of Assertio, dated May 19, 2020, as amended by the Certificate of Amendment to the Amended and Restated Certificate of Incorporation, dated May 13, 2021;

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“Assertio common stock” refers to the common stock, par value $0.0001 per share, of Assertio;

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“Assertio record date” refers to June 13, 2023;

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“Assertio share issuance proposal” refers to the proposal to approve the issuance of shares of Assertio common stock to Spectrum stockholders in connection with the Merger, including the issuance of shares of Assertio common stock as payments under the CVRs;

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“Assertio special meeting” refers to the special meeting of Assertio stockholders to consider and vote upon the Assertio share issuance proposal and the Assertio adjournment proposal;

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“Code” refers to the Internal Revenue Code of 1986, as amended;

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“combined company” refers to Assertio immediately following the completion of the Merger and the other transactions contemplated by the Merger Agreement;

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“CVR” refers to a non-tradeable contingent value right received by holders of Spectrum common stock, representing a contractual right to receive future conditional payments worth up to an aggregate maximum amount of $0.20, settleable in cash, additional shares of Assertio common stock or a combination of cash and additional shares of Assertio common stock, at Assertio’s sole discretion, upon the achievement of certain sales milestones related to Spectrum’s product ROLVEDON (formerly known as ROLONTIS);

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“DGCL” refers to the General Corporation Law of the State of Delaware;

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“effective time” refers to the date and time when the Merger becomes effective under the DGCL, which will be the date and time at which the certificate of merger with respect to the Merger is filed with the Secretary of State of the State of Delaware, or such later date and time as may be mutually agreed to in writing by Assertio and Spectrum and specified in the certificate of merger;

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“Exchange Act” refers to the Securities Exchange Act of 1934, as amended;

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“exchange ratio” refers to 0.1783, which figure reflects the number of shares of Assertio common stock that Spectrum stockholders will be entitled to receive as Upfront Merger Consideration in the Merger for each share of Spectrum common stock held immediately prior to the effective time;

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“GAAP” refers to U.S. generally accepted accounting principles;

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“Guggenheim Securities” refers to Guggenheim Securities, LLC, financial advisor to Spectrum in connection with the proposed Merger;

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“Wainwright” refers to H.C. Wainwright & Co., LLC, financial advisor to Assertio in connection with the proposed Merger;

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“HSR Act” refers to the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended;

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“Merger” refers to the merger of Merger Sub with and into Spectrum;

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“Merger Agreement” refers to the Agreement and Plan of Merger, dated April 24, 2023, as it may be amended from time to time, by and among Assertio, Merger Sub and Spectrum;

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“Merger Sub” refers to Spade Merger Sub 1, Inc., a Delaware corporation and wholly owned subsidiary of Assertio, formed for the purpose of effecting the Merger as described in this joint proxy statement/prospectus;

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“Nasdaq CM” refers to the Nasdaq Capital Market;

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“Nasdaq SM” refers to the Nasdaq Stock Market LLC;

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“SEC” refers to the U.S. Securities and Exchange Commission;

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“Securities Act” refers to the Securities Act of 1933, as amended;

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“share issuance” refers to the issuance of shares of Assertio common stock to Spectrum stockholders in connection with the Merger;

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“Spectrum” refers to Spectrum Pharmaceuticals, Inc., a Delaware corporation;

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“Spectrum adjournment proposal” refers to the proposal to approve the adjournment of the Spectrum special meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the Spectrum special meeting to approve the Spectrum merger proposal or to ensure that any supplement or amendment to the accompanying joint proxy statement/prospectus is timely provided to Spectrum stockholders;

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“Spectrum board of directors” refers to the board of directors of Spectrum;

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“Spectrum bylaws” refers to the Fourth Amended and Restated Bylaws of Spectrum, dated March 30, 2023;

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“Spectrum charter” refers to the Restated Certificate of Incorporation, dated June 18, 2018;

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“Spectrum common stock” refers to the common stock, par value $0.001 per share, of Spectrum;

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“Spectrum advisory compensation proposal” refers to the proposal to approve, on a non-binding advisory basis, the compensation that may be paid or become payable to Spectrum named executive officers that is based on or otherwise relates to the transactions contemplated by the Merger Agreement;

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“Spectrum merger proposal” refers to the proposal to adopt the Merger Agreement;

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“Spectrum record date” refers to June 13, 2023;

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“Spectrum special meeting” refers to the special meeting of Spectrum stockholders to consider and vote upon the Spectrum merger proposal and related matters;

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“SVB Securities” refers to SVB Securities LLC, financial advisor to Assertio in connection with the proposed Merger; and

•

“Termination Date” refers to October 24, 2023, the date on which, subject to certain limitations in the Merger Agreement, the Merger Agreement may be terminated and the Merger abandoned by either Assertio or Spectrum.

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	Page
QUESTIONS AND ANSWERS		1
SUMMARY		15
SELECTED UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION		30
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS		34
RISK FACTORS		36
THE PARTIES TO THE MERGER		50
THE ASSERTIO SPECIAL MEETING		51
ASSERTIO PROPOSAL 1: APPROVAL OF THE SHARE ISSUANCE		58
ASSERTIO PROPOSAL 2: ADJOURNMENT OF THE ASSERTIO SPECIAL MEETING		59
THE SPECTRUM SPECIAL MEETING		60
SPECTRUM PROPOSAL 1: THE SPECTRUM MERGER PROPOSAL		68
SPECTRUM PROPOSAL 2: THE SPECTRUM ADVISORY COMPENSATION PROPOSAL		69
SPECTRUM PROPOSAL 3: THE SPECTRUM ADJOURNMENT PROPOSAL		70
THE MERGER		71
THE MERGER AGREEMENT		127
THE CONTINGENT VALUE RIGHTS AGREEMENT		153
UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION		156
INTERESTS OF ASSERTIO’S DIRECTORS AND EXECUTIVE OFFICERS IN THE MERGER		167
INTERESTS OF SPECTRUM’S DIRECTORS AND EXECUTIVE OFFICERS IN THE MERGER		168
U.S. FEDERAL INCOME TAX CONSIDERATIONS RELATING TO THE MERGER		169
COMPARISON OF STOCKHOLDERS’ RIGHTS		177
APPRAISAL RIGHTS		188
LEGAL MATTERS		193
EXPERTS		193
CERTAIN BENEFICIAL OWNERS OF ASSERTIO COMMON STOCK		194
CERTAIN BENEFICIAL OWNERS OF SPECTRUM COMMON STOCK		196
STOCKHOLDER PROPOSALS		198
HOUSEHOLDING OF PROXY MATERIALS		198
WHERE YOU CAN FIND MORE INFORMATION		199
ANNEX A — MERGER AGREEMENT		A-1
ANNEX B — FORM OF CVR AGREEMENT		B-1
ANNEX C — SVB SECURITIES LLC OPINION		C-1
ANNEX D — H.C. WAINWRIGHT & CO., LLC OPINION		D-1
ANNEX E — GUGGENHEIM SECURITIES, LLC OPINION		E-1
ANNEX F — SECTION 262 OF THE DGCL		F-1

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QUESTIONS AND ANSWERS

The following are brief answers to certain questions that you, as an Assertio or Spectrum stockholder, may have regarding the Merger and the other matters being considered at the Assertio and Spectrum special meetings, as applicable. You are urged to carefully read this joint proxy statement/prospectus and the other documents referred to in this joint proxy statement/prospectus in their entirety because this section may not provide all the information that is important to you regarding these matters. See “Summary” for a summary of important information regarding the Merger Agreement, the Merger and the related transactions. Additional important information is contained in the annexes to, and the documents incorporated by reference in, this joint proxy statement/prospectus. You may obtain the information incorporated by reference in this joint proxy statement/prospectus, without charge, by following the instructions under “Where You Can Find More Information.”

Why am I receiving this joint proxy statement/prospectus?

You are receiving this joint proxy statement/prospectus because Spectrum has agreed to be acquired by Assertio through a merger of Merger Sub with and into Spectrum, with Spectrum continuing as the surviving corporation in the Merger and becoming a wholly owned subsidiary of Assertio. The Merger Agreement, which governs the terms and conditions of the Merger, is attached as Annex A hereto.

Your vote is required in connection with the Merger. Assertio and Spectrum are sending these materials to their respective stockholders to help them decide how to vote their shares with respect to the share issuance, in the case of Assertio, the adoption of the Merger Agreement, in the case of Spectrum, and other important matters.

What matters am I being asked to vote on?

In order to complete the Merger, among other things:

•

Assertio stockholders must approve the Assertio share issuance proposal; and

•

Spectrum stockholders must approve the Spectrum merger proposal.

Assertio: Assertio is holding the Assertio special meeting to obtain approval of the Assertio share issuance proposal and the Assertio adjournment proposal.

Spectrum: Spectrum is holding the Spectrum special meeting to obtain approval of the Spectrum merger proposal, the Spectrum advisory compensation proposal and the Spectrum adjournment proposal.

Your vote is very important, regardless of the number of shares that you own. The approval of the Assertio share issuance proposal and the Spectrum merger proposal are conditions to the obligations of Assertio and Spectrum to complete the Merger. The approval of the Assertio adjournment proposal, the Spectrum advisory compensation proposal and the Spectrum adjournment proposal are not conditions to the obligations of Assertio or Spectrum to complete the Merger.

When and where will each of the special meetings take place?

Assertio: The Assertio special meeting will be held solely virtually via live webcast on July 27, 2023, beginning at 12:30 p.m., Central Time. Assertio stockholders will be able to virtually attend and vote at the Assertio special meeting by visiting www.cstproxy.com/assertiotx/sm2023, which is referred to as the “Assertio special meeting website.” In order to virtually attend and vote at the Assertio special meeting, you will need the 12-digit control number located on your proxy card. Assertio has retained Continental Stock Transfer & Trust Company, which is referred to as “CST,” to host the live webcast of the Assertio special meeting. On the day of the Assertio special meeting, CST may be contacted at (800) 450-7155 (U.S.) or (857) 999-9155 (international), and will be available to answer any questions regarding how to virtually attend the Assertio special meeting or if you encounter any technical difficulty accessing or during the Assertio special meeting. See “The Assertio Special Meeting — Virtually Attending the Assertio Special Meeting.”

Spectrum: The Spectrum special meeting will be held solely virtually via live webcast on July 27, 2023, beginning at 10:00 a.m., Eastern Time. Spectrum stockholders will be able to virtually attend and vote at the Spectrum special meeting by visiting www.meetnow.global/MYXFZTA, which is referred to as the

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“Spectrum special meeting website.” In order to virtually attend and vote at the Spectrum special meeting, you must first register at the Spectrum special meeting website in order to obtain a unique meeting invitation by electronic mail. Spectrum has retained Computershare Trust Company, N.A., which is referred to as “Computershare,” to host the live webcast of the Spectrum special meeting. On the day of the Spectrum special meeting, Computershare may be contacted at 888-724-2416 (U.S.) or +1 781-575-2748 (international) to answer any questions regarding how to virtually attend the Spectrum special meeting or if you encounter any technical difficulty accessing or during the Spectrum special meeting. See “The Spectrum Special Meeting — Virtually Attending the Spectrum Special Meeting.”

Even if you plan to virtually attend your respective company’s special meeting, Assertio and Spectrum recommend that you vote by proxy in advance as described below so that your vote will be counted if you later decide not to or become unable to virtually attend the applicable special meeting.

If you hold your shares in “street name,” you may virtually attend and vote at your respective company’s special meeting only if you obtain a specific control number from your bank, broker or other nominee giving you the right to vote such shares.

Does my vote matter?

Yes, your vote is very important, regardless of the number of shares that you own. The Merger cannot be completed unless the Assertio share issuance proposal is approved by Assertio stockholders and the Spectrum merger proposal is approved by Spectrum stockholders.

Assertio

•

Assertio Share Issuance Proposal. Assuming a quorum is present at the Assertio special meeting, approval of the Assertio share issuance proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio share issuance proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal to vote on the Assertio share issuance proposal will have the same effect as a vote “AGAINST” the Assertio share issuance proposal. However, assuming a quorum is present at the Assertio special meeting, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio share issuance proposal, voting power will deemed to be withheld with respect to the Assertio share issuance proposal and such failure to provide voting instructions will have no effect on the Assertio share issuance proposal.

•

Assertio Adjournment Proposal. Whether or not a quorum is present at the Assertio special meeting, approval of the Assertio adjournment proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio adjournment proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal to vote on the Assertio adjournment proposal will have the same effect as a vote “AGAINST” the Assertio adjournment proposal. However, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio adjournment proposal, voting power will deemed to be withheld with respect to the Assertio adjournment proposal and such failure to provide voting instructions will have no effect on the Assertio adjournment proposal.

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Spectrum

•

Spectrum merger proposal. Assuming a quorum is present at the Spectrum special meeting, approval of the Spectrum merger proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock entitled to vote at the Spectrum special meeting on the Spectrum merger proposal. The failure to vote by proxy or to virtually attend and vote at the Spectrum special meeting, including an abstention, will have the same effect as a vote “AGAINST” the Spectrum merger proposal (assuming a quorum is present at the Spectrum special meeting).

•

Spectrum advisory compensation proposal. Assuming a quorum is present at the Spectrum special meeting, approval of the Spectrum advisory compensation proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock that are virtually present via the Spectrum special meeting website or represented by proxy and entitled to vote at the Spectrum special meeting. The failure to vote by proxy and to virtually attend and vote at the Spectrum special meeting will have no effect on the Spectrum advisory compensation proposal (assuming a quorum is present at the Spectrum special meeting). Accordingly, assuming a quorum is present at the Spectrum special meeting, any shares not virtually present or represented by proxy (including due to the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Spectrum advisory compensation proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Spectrum special meeting to vote on the Spectrum advisory compensation proposal will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal. In addition, if a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Spectrum advisory compensation proposal, it will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal.

•

Spectrum adjournment proposal. Whether or not a quorum is present at the Spectrum special meeting, approval of the Spectrum adjournment proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock that are virtually present via the Spectrum special meeting website or represented by proxy and entitled to vote at the Spectrum special meeting. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Spectrum adjournment proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Spectrum special meeting on the Spectrum adjournment proposal to vote on the Spectrum adjournment proposal will have the same effect as a vote “AGAINST” the Spectrum adjournment proposal. In addition, if a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Spectrum adjournment proposal, it will have the same effect as a vote “AGAINST” the Spectrum adjournment proposal.

What will Spectrum stockholders receive for their shares of Spectrum common stock if the Merger is completed?

If the Merger is completed, each share of Spectrum common stock outstanding as of immediately prior to the effective time will be converted into the right to receive (i) 0.1783 shares of Assertio common stock, and (ii) one CVR for each share of Spectrum common stock that you own, which is collectively referred to as the “Merger Consideration.” Each Spectrum stockholder will receive cash (without interest and less any applicable withholding taxes) in lieu of any fractional shares of Assertio common stock that such Spectrum stockholder would otherwise receive in the Merger (the “Fractional Share Cash Consideration”). Any cash amounts to be received by a Spectrum stockholder in lieu of fractional shares of Assertio common stock will be rounded to the nearest whole cent. Each CVR will represent a contractual right to receive future conditional Milestone Payments (as defined below) worth up to an aggregate maximum amount of $0.20, settleable in cash, additional shares of Assertio common stock or a combination of cash and additional shares of Assertio common stock, at Assertio’s sole discretion, upon the achievement of certain sales

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milestones related to Spectrum’s product ROLVEDON. The minimum payment on each CVR is zero and the maximum payment is $0.20.

Pursuant to the contingent value rights agreement, which is referred to as the “CVR Agreement,” to be entered into by Assertio and the Rights Agent at or prior to the effective time, each CVR will entitle the holder thereof to receive future conditional payments worth up to an aggregate maximum amount of $0.20, settleable in cash, additional shares of Assertio common stock or a combination of cash and additional shares of Assertio common stock, at Assertio’s sole discretion, as follows:

•

up to $0.10 per CVR upon achievement of net sales of Spectrum’s product ROLVEDON at least $175 million during the 2024 calendar year; and

•

up to $0.10 per CVR upon achievement of net sales of Spectrum’s product ROLVEDON at least $225 million during the 2025 calendar year.

Each of the foregoing payments are referred to as a “Milestone Payment” and each net sales target is referred to as a “Milestone.” Even if a Milestone is satisfied, the amount of each Milestone Payment may be adjusted to an amount less than $0.10 (including zero) if the closing price of Assertio common stock at the closing of the Merger or on the date a notice of a Milestone Payment is sent to holders of the CVRs could result in the value of the Upfront Merger Consideration constituting less than 80% of the aggregate Merger Consideration. A form of the CVR Agreement is attached as Annex B to this proxy statement and is incorporated by reference herein.

Because the Merger Consideration includes CVRs and Assertio will issue a fixed number of shares of Assertio common stock in exchange for each share of Spectrum common stock, the value of the Merger Consideration that Spectrum stockholders will receive in the Merger will depend on both the market price of shares of Assertio common stock at the time the Merger is completed and the achievement of the Milestones. The market price of shares of Assertio common stock that Spectrum stockholders receive at the time the Merger is completed could be greater than, less than or the same as the market price of shares of Assertio common stock on the date of this joint proxy statement/prospectus or at the times of the Assertio and Spectrum special meetings. Accordingly, you should obtain current market quotations for Assertio common stock and Spectrum common stock before deciding how to vote on the Assertio share issuance proposal and the Spectrum merger proposal, as applicable. Assertio common stock is traded on Nasdaq SM under the symbol “ASRT.” Spectrum common stock is traded on Nasdaq CM, under the symbol “SPPI.” Shares of common stock of the combined company will trade on Nasdaq SM under the symbol “ASRT” after completion of the Merger. For more information regarding the Merger Consideration to be received by Spectrum stockholders if the Merger is completed, see “The Merger Agreement — Merger Consideration.”

How does the Merger Consideration compare to the market price of Spectrum common stock prior to the public announcement of the Merger Agreement?

The Upfront Merger Consideration (as defined below) represents a premium of approximately 65% over the closing price of Spectrum common stock on April 24, 2023, the last trading day prior to the public announcement of the execution of the Merger Agreement. The Merger Consideration, assuming achievement of both CVR Milestones and the maximum Milestone Payments thereunder, represents a maximum premium of approximately 94% over the closing price of Spectrum common stock on April 24, 2023, the last trading day prior to the public announcement of the execution of the Merger Agreement.

How does the Assertio board of directors recommend that I vote at the Assertio special meeting?

The Assertio board of directors unanimously recommends that you vote “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal.

Other than with respect to continued service for, employment by and the right to continued indemnification by the combined company, as of the date of this joint proxy statement/prospectus, Assertio directors and executive officers do not have interests in the Merger that are different from, or in addition to, the interests of other Assertio stockholders generally. See “Interests of Assertio’s Directors and Executive Officers in the Merger.”

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How does the Spectrum board of directors recommend that I vote at the Spectrum special meeting?

The Spectrum board of directors recommends that you vote “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal.

In considering the recommendations of the Spectrum board of directors, Spectrum stockholders should be aware that Spectrum directors and executive officers have interests in the Merger that may be different from, or in addition to, their interests as Spectrum stockholders generally. These interests may include, among others, the payment of severance benefits and acceleration of outstanding Spectrum equity awards upon certain terminations of employment or service, the combined company’s agreement to indemnify Spectrum directors and executive officers against certain claims and liabilities, one of Spectrum’s directors will serve as a director on the Assertio board of directors following the merger and certain interests arising from the employment and compensation arrangements of Spectrum’s executive officers and the manner in which they would be affected by the merger. For a more complete description of these interests, see “Interests of Spectrum’s Directors and Executive Officers in the Merger.”

Who is entitled to vote at each special meeting?

Assertio

All holders of record of shares of Assertio common stock who held shares at the close of business on June 13, 2023 (the “Assertio record date”) are entitled to receive notice of, and to vote at, the Assertio special meeting. Each such holder of Assertio common stock is entitled to cast one vote on each matter properly brought before the Assertio special meeting for each share of Assertio common stock that such holder owned of record as of the Assertio record date. Virtual attendance at the Assertio special meeting via the Assertio special meeting website is not required to vote. See below and “The Assertio Special Meeting — Methods of Voting” for instructions on how to vote without virtually attending the Assertio special meeting.

Spectrum

All holders of record of shares of Spectrum common stock who held shares at the close of business on June 13, 2023 (the “Spectrum record date”) are entitled to receive notice of, and to vote at, the Spectrum special meeting. Each such holder of Spectrum common stock is entitled to cast one vote on each matter properly brought before the Spectrum special meeting for each share of Spectrum common stock that such holder owned of record as of the Spectrum record date. Virtual attendance at the Spectrum special meeting via the Spectrum special meeting website is not required to vote. See below and “The Spectrum Special Meeting — Methods of Voting” for instructions on how to vote without virtually attending the Spectrum special meeting.

What is a proxy?

A proxy is a stockholder’s legal designation of another person to vote shares owned by such stockholder on their behalf. The document used to designate a proxy to vote your shares of Assertio or Spectrum common stock, as applicable, is referred to as a “proxy card.”

How many votes do I have at each special meeting?

Assertio

Each Assertio stockholder is entitled to one vote for each share of Assertio common stock held of record as of the close of business on the Assertio record date. As of the close of business on the Assertio record date, there were 56,512,962 shares of Assertio common stock outstanding.

Spectrum

Each Spectrum stockholder is entitled to one vote for each share of Spectrum common stock held of record as of the close of business on the Spectrum record date. As of the close of business on the Spectrum record date, there were 205,245,727 shares of Spectrum common stock outstanding.

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What constitutes a quorum for each special meeting?

Assertio

A quorum is the minimum number of shares required to be represented, either through virtual attendance or through representation by proxy, to hold a valid meeting.

The holders of record of 331∕3% of the issued and outstanding shares of Assertio common stock entitled to vote at the Assertio special meeting must be virtually present via the Assertio special meeting website or represented by proxy in order to constitute a quorum.

Spectrum

A quorum is the minimum number of shares required to be represented, either through virtual attendance or through representation by proxy, to hold a valid meeting.

What will the holders of Spectrum stock options, restricted stock awards and restricted stock units receive in the Merger?

At the effective time, each option (other than an option under the Spectrum Employee Stock Purchase Plan) granted under Spectrum’s 2009 Equity Incentive Plan, 2018 Equity Incentive Plan, 2022 Employment Inducement Incentive Award Plan or any other equity incentive plan or arrangement (the “Spectrum Equity Plans”) to purchase Spectrum common stock (each, a “Spectrum Stock Option”) and each stock appreciation right with respect to Spectrum common stock granted under any Spectrum Equity Plan (each, a “Spectrum SAR”), that, in each case, is outstanding immediately prior to the effective time, will, if unvested, become vested and treated as follows:

•

Spectrum Stock Options and Spectrum SARs with an exercise price per share that is less than the value of the Upfront Merger Consideration will be converted into the right to receive (1) a number of shares of Assertio common stock determined based on the difference between value of the Upfront Merger Consideration and the exercise price of such Spectrum Stock Option or Spectrum SAR and (2) a number of CVRs equal to the number of shares of Spectrum common stock underlying such Spectrum Stock Option or Spectrum SAR;

•

Spectrum Stock Options or Spectrum SARs with an exercise price per share that is equal to or greater than the value of the Upfront Merger Consideration and less than the sum of the Upfront Merger Consideration and the maximum amount payable under a CVR will not receive any Assertio common stock, but will receive a number of CVRs equal to the number of shares of Spectrum common stock underlying such Spectrum Stock Option or Spectrum SAR, provided that the payment under such CVRs, if any, will be reduced by the amount by which the exercise price per share exceeds the value of the Upfront Merger Consideration; and

•

Spectrum Stock Options or Spectrum SARs with an exercise price per share that is equal to or greater than the value of the Merger Consideration will be canceled for no consideration.

At the effective time, each restricted stock unit granted under any Spectrum Equity Plan (each, a “Spectrum RSU”), whether vested or unvested, that is outstanding immediately prior to the effective time will, if unvested, become vested, and the holder of such Spectrum RSUs will automatically and without any required action on the part of the holder thereof or Spectrum, receive the Merger Consideration.

At the effective time, each share of Spectrum common stock underlying an unvested restricted stock award granted under any Spectrum Equity Incentive Plan (each, an “RSA Share”) that is outstanding immediately prior to the effective time will become vested and be treated as specified in the Merger Agreement.

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To the extent Assertio and any holder of Spectrum Stock Options, Spectrum SARs, Spectrum RSUs or RSA Shares agree in writing to treatment of such equity different than as described above, the terms of such written agreement will apply in lieu of the treatment described above.

Where will the Assertio common stock that I receive in the Merger be publicly traded?

The shares of Assertio common stock to be issued to Spectrum stockholders in the Merger will be listed for trading on Nasdaq SM under the symbol “ASRT.”

What happens if the Merger is not completed?

If the Assertio share issuance proposal is not approved by Assertio stockholders, if the Spectrum merger proposal is not approved by Spectrum stockholders or if the Merger is not completed for any other reason, Spectrum stockholders will not receive the Merger Consideration or any other consideration in connection with the Merger, and their shares of Spectrum common stock will remain outstanding.

If the Merger is not completed, Spectrum will remain an independent public company, the Spectrum common stock will continue to be listed and traded on Nasdaq CM under the symbol “SPPI” and Assertio will not complete the share issuance contemplated by the Merger Agreement, regardless of whether the Assertio share issuance proposal has been approved by Assertio stockholders.

If the Merger Agreement is terminated under specified circumstances, including if the Spectrum board of directors changes its recommendation, Spectrum may be required to pay Assertio a termination fee of $8.3 million, less expenses previously paid by Spectrum to Assertio. If the Merger Agreement is terminated as a result of a failure of the Spectrum merger proposal, then Spectrum may be required to reimburse Assertio’s out-of-pocket expenses in connection with the proposed Merger, up to a maximum amount of $1,000,000. If the Merger Agreement is terminated under other specified circumstances, including if the Assertio board of directors changes its recommendation, Assertio may be required to pay Spectrum a termination fee of $8.3 million, less expenses previously paid by Assertio to Spectrum. If the Merger Agreement is terminated as a result of a failure of the Assertio share issuance proposal, then Assertio may be required to reimburse Spectrum’s out-of-pocket expenses in connection with the proposed Merger, up to a maximum amount of $1,000,000. See “The Merger Agreement — Termination Fees.”

How can I virtually vote my shares at my respective special meeting?

Assertio

Shares held directly in your name as an Assertio stockholder of record may be virtually voted at the Assertio special meeting via the Assertio special meeting website. You will need the 12-digit control number included on your proxy card in order to access and vote via the Assertio special meeting website as described under “The Assertio Special Meeting — Virtually Attending the Assertio Special Meeting.”

Shares held in “street name” may be virtually voted at the Assertio special meeting via the Assertio special meeting website only if you obtain a specific control number and follow the instructions provided by your bank, broker or other nominee. See “The Assertio Special Meeting — Virtually Attending the Assertio Special Meeting.”

Spectrum

Shares held directly in your name as a Spectrum stockholder of record may be virtually voted at the Spectrum special meeting via the Spectrum special meeting website. In order to virtually attend and vote at the Spectrum special meeting, you must first register at the Spectrum special meeting website in order to obtain a unique meeting invitation by electronic mail.

Shares held in “street name” may be virtually voted at the Spectrum special meeting via the Spectrum special meeting website only if you obtain a specific control number and follow the instructions provided by your, broker or other nominee. See “The Spectrum Special Meeting — Virtually Attending the Spectrum Special Meeting.”

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Even if you plan to virtually attend your respective company’s special meeting via the applicable special meeting website, Assertio and Spectrum recommend that you vote by proxy in advance as described below so that your vote will be counted if you later decide not to or become unable to virtually attend the respective special meeting.

For additional information on virtually attending the special meetings, see “The Assertio Special Meeting” and “The Spectrum Special Meeting.”

How can I vote my shares without virtually attending my company’s special meeting?

Whether you hold your shares directly as a stockholder of record of Assertio or Spectrum or beneficially in “street name,” you may direct your vote by proxy without virtually attending the Assertio or Spectrum special meeting, as applicable. If you are a stockholder of record, you can vote by proxy over the internet, by telephone or by mail by following the instructions provided in the enclosed proxy card. If you hold shares beneficially in “street name,” you should follow the voting instructions provided by your bank, broker or other nominee.

For additional information on voting procedures, see “The Assertio Special Meeting” and “The Spectrum Special Meeting.”

What is a “broker non-vote”?

Under Nasdaq CM and Nasdaq SM (collectively, “Nasdaq”), rules, banks, brokers and other nominees may use their discretion to vote “uninstructed” shares (i.e., shares of record held by banks, brokers or other nominees, but with respect to which the beneficial owner of such shares has not provided instructions on how to vote on a particular proposal) with respect to matters that are considered to be “routine,” but not with respect to “non-routine” matters. All of the proposals currently expected to be brought before the Assertio and Spectrum special meetings are “non-routine” matters under Nasdaq rules.

A “broker non-vote” occurs on an item when (i) a bank, broker or other nominee has discretionary authority to vote on one or more proposals to be voted on at a meeting of stockholders, but is not permitted to vote on other proposals without instructions from the beneficial owner of the shares, and (ii) the beneficial owner fails to provide the bank, broker or other nominee with such instructions. Because all of the proposals currently expected to be voted on at the Assertio and Spectrum special meetings are non-routine matters under Nasdaq rules for which brokers do not have discretionary authority to vote, Assertio and Spectrum do not expect there to be any broker non-votes at the Assertio or Spectrum special meetings.

What stockholder vote is required for the approval of each proposal at the Assertio special meeting? What will happen if I fail to vote or abstain from voting on each proposal at the Assertio special meeting?

Assertio Proposal 1: Assertio Share Issuance Proposal

Assuming a quorum is present at the Assertio special meeting, approval of the Assertio share issuance proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio share issuance proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal to vote on the Assertio share issuance proposal will have the same effect as a vote “AGAINST” the Assertio share issuance proposal. However, assuming a quorum is present at the Assertio special meeting, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio share issuance proposal, voting power will deemed to be withheld with respect to the Assertio share issuance proposal and such failure to provide voting instructions will have no effect on the Assertio share issuance proposal.

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Assertio Proposal 2: Assertio Adjournment Proposal

Whether or not a quorum is present at the Assertio special meeting, approval of the Assertio adjournment proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio adjournment proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal to vote on the Assertio adjournment proposal will have the same effect as a vote “AGAINST” the Assertio adjournment proposal. However, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio adjournment proposal, voting power will deemed to be withheld with respect to the Assertio adjournment proposal and such failure to provide voting instructions will have no effect on the Assertio adjournment proposal.

What stockholder vote is required for the approval of each proposal at the Spectrum special meeting? What will happen if I fail to vote or abstain from voting on each proposal at the Spectrum special meeting?

Spectrum Proposal 1: Spectrum Merger Proposal

Assuming a quorum is present at the Spectrum special meeting, approval of the Spectrum merger proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock entitled to vote at the Spectrum special meeting on the Spectrum merger proposal. Accordingly, an abstention or other failure to vote on the Spectrum merger proposal will have the same effect as a vote “AGAINST” the Spectrum merger proposal.

Spectrum Proposal 2: Spectrum advisory Compensation Proposal

Assuming a quorum is present at the Spectrum special meeting, approval of the Spectrum advisory compensation proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock that are virtually present via the Spectrum special meeting website or represented by proxy and entitled to vote at the Spectrum special meeting. Accordingly, assuming a quorum is present at the Spectrum special meeting, any shares not virtually present or represented by proxy (including due to the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Spectrum advisory compensation proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Spectrum special meeting to vote on the Spectrum advisory compensation proposal will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal. In addition, if a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Spectrum advisory compensation proposal, it will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal.

Spectrum Proposal 3: Spectrum Adjournment Proposal

Whether or not a quorum is present at the Spectrum special meeting, approval of the Spectrum adjournment proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Spectrum common stock that are virtually present via the Spectrum special meeting website or represented by proxy and entitled to vote at the Spectrum special meeting. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Spectrum adjournment proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Spectrum special meeting to vote on the Spectrum adjournment proposal will have the same effect as

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a vote “AGAINST” the Spectrum adjournment proposal. In addition, if a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Spectrum adjournment proposal, it will have the same effect as a vote “AGAINST” the Spectrum adjournment proposal.

Why am I being asked to consider and vote on a proposal to approve, by non-binding advisory vote, the Merger-related compensation for Spectrum named executive officers (the Spectrum advisory compensation proposal)?

Under SEC rules, Spectrum is required to seek a non-binding advisory vote of its stockholders relating to the compensation that may be paid or become payable to Spectrum named executive officers that is based on or otherwise relates to the Merger (also known as “golden parachute” compensation).

What happens if Spectrum stockholders do not approve, by non-binding advisory vote, the Merger-related compensation for Spectrum named executive officers (the Spectrum advisory compensation proposal)?

Because the vote on the proposal to approve the Spectrum advisory compensation proposal is advisory in nature, the outcome of the vote will not be binding upon Spectrum or the combined company. Accordingly, the Merger-related compensation, which is described under “Interests of Spectrum’s Directors and Executive Officers in the Merger,” may be paid to Spectrum named executive officers even if Spectrum stockholders do not approve the Spectrum advisory compensation proposal.

What if I hold shares of both Assertio and Spectrum common stock?

If you are both an Assertio stockholder and a Spectrum stockholder, you will receive two separate packages of proxy materials. A vote cast as an Assertio stockholder will not count as a vote cast as a Spectrum stockholder, and a vote cast as a Spectrum stockholder will not count as a vote cast as an Assertio stockholder. Therefore, please follow the instructions received with each set of materials you receive in order to submit separate proxies for your shares of Assertio common stock and your shares of Spectrum common stock.

What is the difference between holding shares as a stockholder of record and as a beneficial owner of shares held in “street name”?

If your shares of Assertio or Spectrum common stock are registered directly in your name with the transfer agent of Assertio and Spectrum, respectively, you are considered the stockholder of record with respect to those shares. As the stockholder of record, you have the right to vote directly at the applicable special meeting. You may also grant a proxy directly to Assertio or Spectrum, as applicable, or to a third party to vote your shares at the applicable special meeting.

If your shares of Assertio or Spectrum common stock are held by a bank, broker or other nominee, you are considered the beneficial owner of shares held in “street name.” Your bank, broker or other nominee will send you, as the beneficial owner, a package describing the procedures for voting your shares. You should follow the instructions provided by them to vote your shares. In order to virtually attend and vote at the Assertio special meeting via the Assertio special meeting website or the Spectrum special meeting via the Spectrum special meeting website, you will need to obtain a specific control number and follow the other procedures provided by your bank, broker or other nominee.

If my shares of Assertio or Spectrum common stock are held in “street name” by my bank, broker or other nominee, will my bank, broker or other nominee automatically vote those shares for me?

No. Your bank, broker or other nominee will only be permitted to vote your shares of Assertio or Spectrum common stock, as applicable, if you instruct your bank, broker or other nominee how to vote. You should follow the procedures provided by your bank, broker or other nominee regarding the voting of your shares. Under Nasdaq rules, banks, brokers and other nominees who hold shares of Assertio or Spectrum common stock in “street name” for their customers have authority to vote on “routine” proposals when they have not received instructions from beneficial owners. However, banks, brokers and other nominees are prohibited from exercising their voting discretion with respect to non-routine matters, which include all the proposals currently scheduled to be considered and voted on at the Assertio and Spectrum special

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meetings. As a result, absent specific instructions from the beneficial owner of such shares, banks, brokers and other nominees are not empowered to vote such shares.

For Assertio stockholders, the effect of not instructing your bank, broker or other nominee how you wish to vote your shares of Assertio common stock will have no effect on the Assertio share issuance proposal or the Assertio adjournment proposal (assuming a quorum is present at the Assertio special meeting).

For Spectrum stockholders, the effect of not instructing your bank, broker or other nominee how you wish to vote your shares of Spectrum common stock will be the same as a vote “AGAINST” the Spectrum merger proposal, but will have no effect on the Spectrum advisory compensation proposal (assuming a quorum is present at the Spectrum special meeting) or the adjournment proposal. In addition, if a Spectrum stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Spectrum advisory compensation proposal or the Spectrum adjournment proposal, it will have the same effect as a vote “AGAINST” such proposal.

What should I do if I receive more than one set of voting materials for the same special meeting?

If you hold shares of Assertio or Spectrum common stock in “street name” and also directly in your name as a stockholder of record or otherwise, or if you hold shares of Assertio or Spectrum common stock in more than one brokerage account, you may receive more than one set of voting materials relating to the same special meeting.

Record Holders. For shares held directly, please vote by proxy over the internet or telephone using the instructions included with the accompanying proxy card, or promptly complete your proxy card and return it in the enclosed postage-paid envelope, in order to ensure that all of your shares of Assertio or Spectrum common stock are voted.

Shares in “street name.” For shares held in “street name” through a bank, broker or other nominee, you should follow the procedures provided by your bank, broker or other nominee to submit a proxy or vote your shares.

If a stockholder gives a proxy, how are the shares of Assertio or Spectrum common stock voted?

Regardless of the method you choose to vote, the individuals named on the enclosed proxy card will vote your shares of Assertio or Spectrum common stock, as applicable, in the way that you indicate. For each item before the Assertio or Spectrum special meeting, as applicable, you may specify whether your shares of Assertio or Spectrum common stock, as applicable, should be voted for or against, or abstain from voting.

How will my shares of Assertio common stock be voted if I return a blank proxy?

If you sign, date and return your proxy and do not indicate how you want your shares of Assertio common stock to be voted, then your shares of Assertio common stock will be voted in accordance with the recommendation of the Assertio board of directors: “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal.

How will my shares of Spectrum common stock be voted if I return a blank proxy?

If you sign, date and return your proxy and do not indicate how you want your shares of Spectrum common stock to be voted, then your shares of Spectrum common stock will be voted in accordance with the recommendation of the Spectrum board of directors: “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal.

Can I change my vote after I have submitted my proxy?

Any Assertio or Spectrum stockholder giving a proxy has the right to revoke the proxy and change their vote before the proxy is voted at the applicable special meeting by doing any of the following:

•

subsequently submitting a new proxy (including over the internet or telephone) for the applicable special meeting that is received by the deadline specified on the accompanying proxy card;

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•

giving written notice of your revocation to Assertio’s or Spectrum’s Corporate Secretary, as applicable; or

•

virtually attending and voting at the applicable special meeting via the applicable special meeting website.

Execution or revocation of a proxy will not in any way affect your right to virtually attend and vote at the applicable special meeting via the applicable special meeting website. Written notices of revocation and other communications relating to the revocation of proxies should be addressed:

	If you are an Assertio stockholder:			If you are a Spectrum stockholder:
	Assertio Holdings, Inc. Attn: General Counsel corpgov@assertiotx.com 100 South Saunders Road, Suite 300 Lake Forest, IL 60045			Spectrum Pharmaceuticals, Inc. Attn: Corporate Secretary corporate.secretary@spectrum.com Pilot House — Lewis Wharf 2 Atlantic Avenue, 6th Floor Boston, MA 02110

See “The Assertio Special Meeting — Revocability of Proxies” and “The Spectrum Special Meeting — Revocability of Proxies.”

If I hold my shares in “street name,” can I change my voting instructions after I have submitted voting instructions to my bank, broker or other nominee?

If your shares are held in the name of a bank, broker or other nominee and you previously provided voting instructions to your bank, broker or other nominee, you should follow the instructions provided by your bank, broker or other nominee to revoke or change your voting instructions.

Where can I find the voting results of the special meetings?

The preliminary voting results for each special meeting are expected to be announced at that special meeting. In addition, within four business days following certification of the final voting results, each of Assertio and Spectrum will file the final voting results of its respective special meeting (or, if the final voting results have not yet been certified, the preliminary results) with the SEC on a Current Report on Form 8-K.

If I am an Assertio stockholder and I oppose the Assertio share issuance proposal or if I am a Spectrum stockholder and I oppose the Spectrum merger proposal or the Spectrum merger compensation advisory proposal, but all such proposals are approved, what are my rights?

Under Delaware law, Assertio stockholders are not entitled to dissenters’ or appraisal rights in connection with the issuance of shares of Assertio common stock as contemplated by the Merger Agreement. Assertio stockholders may vote against the Assertio share issuance proposal if they do not favor such proposals.

Spectrum stockholders are entitled to appraisal rights under Section 262 of the DGCL, provided they satisfy the special criteria and conditions set forth in Section 262 of the DGCL. Spectrum common stock held by stockholders that do not vote for approval of the Merger and make a demand for appraisal in accordance with the DGCL will not be converted into Assertio common stock, but will be converted into the right to receive from the combined company consideration determined in accordance with Delaware law.

For more information regarding dissenters’ or appraisal rights, please see “Appraisal Rights.”

Are there any risks that I should consider in deciding whether to vote for the approval of the Assertio share issuance proposal or the Spectrum merger proposal?

Yes. You should read and carefully consider the risk factors set forth under “Risk Factors.” You also should read and carefully consider the risk factors relating to Assertio and Spectrum that are contained in the documents that are incorporated by reference in this joint proxy statement/prospectus.

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What happens if I sell my shares of Assertio or Spectrum common stock after the respective record date but before the respective special meeting?

The Assertio record date is earlier than the date of the Assertio special meeting, and the Spectrum record date is earlier than the date of the Spectrum special meeting. If you sell or otherwise transfer your shares of Assertio or Spectrum common stock after the applicable record date but before the applicable special meeting, you will, unless special arrangements are made, retain your right to vote at the applicable special meeting.

Who will solicit and pay the cost of soliciting proxies?

Assertio has engaged Alliance Advisors, LLC, which is referred to as “Alliance,” to assist in the solicitation of proxies for the Assertio special meeting. Assertio estimates that it will pay Alliance a fee of approximately $65,000, plus reimbursement for certain out-of-pocket fees and expenses. Assertio has agreed to indemnify Alliance against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

Spectrum has engaged Innisfree M&A Incorporated, which is referred to as “Innisfree,” to assist in the solicitation of proxies for the Spectrum special meeting. Spectrum estimates that it will pay Innisfree a fee of approximately $25,000, plus reimbursement for certain out-of-pocket fees and expenses. Spectrum has agreed to indemnify Innisfree against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions).

Assertio and Spectrum also may be required to reimburse banks, brokers and other custodians, nominees and fiduciaries or their respective agents for their expenses in forwarding proxy materials to beneficial owners of Assertio and Spectrum common stock, respectively. Assertio and Spectrum directors, officers and employees also may solicit proxies by telephone, by electronic means or in person. They will not be paid any additional amounts for soliciting proxies.

When is the Merger expected to be completed?

Subject to the satisfaction or waiver of the closing conditions described under “The Merger Agreement — Conditions to the Completion of the Merger,” including approval of the Assertio share issuance proposal by Assertio stockholders and approval of the Spectrum merger proposal by Spectrum stockholders, the Merger is currently expected to be completed in the third quarter of the 2023 calendar year. However, neither Assertio nor Spectrum can predict the actual date on which the Merger will be completed, or if the Merger will be completed at all, because completion of the Merger is subject to conditions and factors beyond the control of both companies, including the receipt of certain required regulatory approvals. Assertio and Spectrum hope to complete the Merger as soon as reasonably practicable. Also see “The Merger — Regulatory Approvals.”

What respective equity stakes will Assertio and Spectrum stockholders hold in the combined company immediately following the Merger?

Based on the number of shares of Assertio and Spectrum common stock outstanding on June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, upon completion of the Merger (without consideration of the shares of Assertio common stock underlying the CVRs), former Spectrum stockholders are expected to own approximately 35% of the outstanding shares of Assertio common stock and Assertio stockholders immediately prior to the Merger are expected to own approximately 65% of the outstanding shares of Assertio common stock. The relative ownership interests of Assertio stockholders and former Spectrum stockholders in the combined company immediately following the Merger will depend on the number of shares of Assertio and Spectrum common stock issued and outstanding immediately prior to the Merger.

If I am a Spectrum stockholder, how will I receive the Merger Consideration to which I am entitled?

If you hold your shares of Spectrum common stock in book-entry form, whether through The Depository Trust Company, which is referred to as “DTC,” or otherwise, you will not be required to take

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any specific actions to exchange your shares of Spectrum common stock for shares of Assertio common stock. Such shares will, following the effective time, be automatically exchanged for shares of Assertio common stock (in book-entry form) and cash in lieu of any fractional shares of Assertio common stock to which you are entitled. If you instead hold your shares of Spectrum common stock in certificated form, then, after receiving the proper documentation from you following the effective time, the Exchange Agent will deliver to you the shares of Assertio common stock (in book-entry form) and cash in lieu of any fractional shares of Assertio common stock to which you are entitled. See “The Merger Agreement — Exchange of Shares.”

What are the U.S. federal income tax consequences of the Merger to holders of Spectrum common stock?

Assertio and Spectrum intend that, for U.S. federal income tax purposes, the Merger qualifies as a “reorganization” within the meaning of Section 368(a) of the Code (the “Intended Tax Treatment”). It is a condition to Spectrum’s obligation to consummate the Merger that Spectrum receive an opinion, dated as of the closing date, from Gibson, Dunn & Crutcher LLP or such other nationally recognized tax counsel reasonably acceptable to Spectrum and Assertio, to the effect that, on the basis of facts, representations, assumptions and exclusions set forth or referred to in such opinion, the Merger will qualify for the Intended Tax Treatment. Assuming the Merger qualifies for the Intended Tax Treatment, a holder of shares of Spectrum common stock who is subject to U.S. federal income taxation generally, subject to the following sentence, is expected to recognize gain (but not loss) for U.S. federal income tax purposes upon the exchange of such for shares of Assertio common stock and the CVRs in the Merger in an amount equal to the lesser of (i) any gain realized with respect to such shares of Spectrum common stock and (ii) the fair market value of the CVRs. The U.S. federal income tax consequences of the Merger are subject to substantial uncertainty, particularly if Milestone Payments are paid in Assertio common stock, in which case it is possible such common stock is treated as additional Assertio common stock received in the Merger which generally would not be taxable upon receipt.

See “U.S. Federal Income Tax Considerations Relating to the Merger” on page 169 of this proxy statement/prospectus for a more complete description of U.S. federal income tax considerations relating to the Merger for holders of shares of Spectrum common stock. You are urged to consult your tax advisors with respect to such uncertainty and the specific consequences of the Merger to you.

What should I do now?

You should read this joint proxy statement/prospectus carefully and in its entirety, including the annexes. Then, you may vote by proxy over the internet or telephone using the instructions included with the accompanying proxy card, or promptly complete your proxy card and return it in the enclosed postage-paid envelope, so that your shares will be voted in accordance with your instructions.

How can I find more information about Assertio and Spectrum?

You can find more information about Assertio and Spectrum from various sources described under “Where You Can Find More Information.”

Whom do I call if I have questions about the special meetings or the Merger?

If you have questions about the special meetings or the Merger, or desire additional copies of this joint proxy statement/prospectus or additional proxies, you may contact your company’s proxy solicitor:

	If you are an Assertio stockholder:			If you are a Spectrum stockholder:
	Alliance Advisors, LLC 200 Broadacres Drive, 3rd Floor Bloomfield, NJ 07003 (973) 873-7700 Banks and Brokers: (973) 518-3365 ASRT@allianceadvisors.com			Innisfree M&A Incorporated 501 Madison Avenue, 20th Floor New York, New York 10022 (877) 800-5185 Banks and Brokers: (212) 750-5833

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SUMMARY

For your convenience, provided below is a brief summary of certain information contained in this joint proxy statement/prospectus. This summary highlights selected information from this joint proxy statement/ prospectus and does not contain all of the information that may be important to you as an Assertio or Spectrum stockholder. To understand the Merger fully and for a more complete description of the terms of the Merger, you should read carefully this entire joint proxy statement/prospectus, its annexes and the other documents to which you are referred. Items in this summary include a page reference directing you to a more complete description of those items. You may obtain the information incorporated by reference in this joint proxy statement/prospectus, without charge, by following the instructions under “Where You Can Find More Information.”

The Parties to the Merger (Page 50)

Assertio Holdings, Inc.

Assertio is a commercial pharmaceutical company offering differentiated products to patients utilizing a non-personal promotional model. Assertio’s commercial portfolio of branded products focuses on three areas: neurology, rheumatology, and pain and inflammation. Assertio has built its commercial portfolio through a combination of increased opportunities with existing products, as well as through the acquisition or licensing of additional approved products. Assertio’s principal executive offices are located at 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045 and its telephone number is (224) 419-7106.

Spectrum Pharmaceuticals, Inc.

Spectrum is a commercial-stage biopharmaceutical company, with a strategy of acquiring, developing, and commercializing novel and targeted oncology therapies. Spectrum has an in-house clinical development organization with regulatory and data management capabilities, in addition to commercial infrastructure and a field based sales force for our marketed product, ROLVEDON™ (eflapegrastim). Spectrum’s principal executive offices are located at Pilot House — Lewis Wharf, 2 Atlantic Avenue, 6th Floor, Boston, Massachusetts 02110 and its telephone number is (617) 586-3900.

Spade Merger Sub 1, Inc.

Merger Sub was formed by Assertio solely in contemplation of the Merger, has not conducted any business and has no assets, liabilities or obligations of any nature other than as set forth in the Merger Agreement. By operation of the Merger, Merger Sub will be merged with and into Spectrum, with Spectrum continuing as the surviving corporation and as a wholly owned subsidiary of Assertio. Merger Sub’s principal executive offices are located at 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045, and its telephone number is (224) 419-7106.

The Merger and the Merger Agreement (Pages 71 and 127)

The terms and conditions of the Merger are contained in the Merger Agreement, a copy of which is attached as Annex A hereto. Assertio and Spectrum encourage you to read the Merger Agreement carefully and in its entirety, as it is the legal document that governs the Merger.

The Merger Agreement provides that, subject to the terms and conditions of the Merger Agreement, Merger Sub will be merged with and into Spectrum, with Spectrum continuing as the surviving corporation in the Merger and as a wholly owned subsidiary of Assertio.

Merger Consideration (Page 71)

At the effective time, each share of Spectrum common stock (other than (i) shares held in treasury by Spectrum or held directly by Assertio or Merger Sub, which shares will be cancelled or (ii) shares that are held by any holder who is entitled to demand and properly demands appraisal of such shares of Spectrum common stock pursuant to, and in compliance with, Section 262 of the DGCL) that was issued and outstanding immediately prior to the effective time will be converted into (A) the right to receive 0.1783 of a fully paid and non-assessable share of common stock, par value $0.0001 per share, of Assertio, and, if

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applicable, cash in lieu of fractional shares (without interest and less any applicable withholding taxes) (the “Upfront Merger Consideration”), and (B) one non-tradeable contingent value right (a “CVR,” and, together with the Upfront Merger Consideration, the “Merger Consideration”), which shall represent the right to receive the Milestone Payments (as defined below), at the times and in the forms provided in the contingent value rights agreement to be entered into (the “CVR Agreement”), a form of which is attached as Annex B to this joint proxy statement/prospectus.

Each CVR will represent a contractual right to receive future conditional payments worth up to an aggregate maximum amount of $0.20, which amount is settleable in cash, additional shares of Assertio common stock or a combination of cash and additional shares of Assertio common stock, at Assertio’s sole discretion, upon the achievement of certain sales milestones related to Spectrum’s product ROLVEDON. The minimum payment on each CVR is zero and the maximum payment is $0.20.

Pursuant to the CVR Agreement, to be entered into by Assertio and Spectrum prior to the effective time, each CVR will entitle the holder thereof to receive future conditional payments worth up to an aggregate maximum amount of $0.20, as follows:

•

up to $0.10 per CVR upon achievement of net sales of Spectrum’s product ROLVEDON of at least $175 million during the 2024 calendar year (the “2024 Annual Net Sales Milestone”); and

•

up to $0.10 per CVR upon achievement of net sales of Spectrum’s product ROLVEDON of at least $225 million during the 2025 calendar year (the “2025 Annual Net Sales Milestone”).

The exchange ratio is fixed, which means that it will not change between now and the date of the Merger, regardless of whether the market price of Assertio or Spectrum common stock changes. If any payment pursuant to the CVR is settled in Assertio common stock, the number of shares of Assertio common stock payable thereunder will be calculated based on the closing price of Assertio common stock on the applicable Milestone Payment date.

As described further in “The Merger Agreement — Exchange of Shares” on page 129 of this proxy statement, prior to the effective time, Assertio will deposit, or cause to be deposited with the Exchange Agent (defined below), (i) cash sufficient to pay the Fractional Share Cash Consideration and (ii) evidence of Assertio common stock in book-entry form representing the number of shares of Assertio common stock sufficient to deliver the aggregate Upfront Merger Consideration payable to Spectrum stockholders in the Merger. Following the completion of the Merger, after (i) a Spectrum stockholder that is the holder of record of an outstanding certificate or outstanding certificates representing shares of Spectrum common stock that has provided the Exchange Agent with such stockholder’s stock certificates and a letter of transmittal, or (ii) in the case of holders of non-certificated shares of Spectrum common stock represented by book-entry (“Spectrum book-entry shares”), the Exchange Agent will promptly pay the stockholder the Upfront Merger Consideration to which such stockholder is entitled without the need for receipt of any further documentation, including any “agent’s message” or other evidence of surrender.

With respect to the CVRs, if any Milestone is attained, then on or prior to the applicable Milestone Determination Date (as defined in the CVR Agreement), Assertio will deposit, or cause to be deposited, with the rights agent (the “Rights Agent”), other than any Milestone Payment amounts to be paid in cash to holders of Spectrum equity incentive awards, in the form of either (A) solely shares of Assertio common stock, (B) solely cash, or (C) a combination of shares of Assertio common stock and cash, at Assertio’s election and subject to the valuation methodology set forth in the CVR Agreement. Following the Rights Agent’s receipt of such deposit from Assertio, the Rights Agent will pay the applicable Milestone Payment to each Spectrum stockholder either by check mailed to their registered address, as reflected in the CVR Register (as defined in the CVR Agreement) as of the close of business on the last business day prior to such Milestone Payment Date (as defined in the CVR Agreement) or in the event that any Milestone Payment

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payable to the CVR holders includes shares of Assertio common stock, Assertio and the Rights Agent shall take such actions as are necessary to issue or transfer to each CVR holder such holders shares of Assertio common stock, in accordance with applicable law.

Treatment of Options and Other Equity-Based Awards (Page 130)

Spectrum Stock Options

At the effective time, each option (other than an option under Spectrum’s employee stock purchase plan) (each, a “Spectrum Stock Option”) to purchase shares of Spectrum common stock granted under any of Spectrum’s equity incentive plans that is outstanding as of immediately prior to the effective time, will, if unvested, become vested, and automatically and without any required action on the part of the holder of such Spectrum Stock Option or Spectrum, be cancelled and treated as follows:

•

With respect to any Spectrum Stock Options with an exercise price per share that is less than the value of the Upfront Merger Consideration, converted into the right to receive (i) a number of shares of Assertio common stock, subject to certain exceptions with respect to fractional shares and any applicable withholdings, that is equal to the quotient of (A) the product of (x) the total number of shares of Spectrum common stock underlying the Spectrum Stock Option multiplied by (y) the excess, if any, of the value of the Upfront Consideration over the exercise price of such Spectrum Stock Option, divided by (B) the average of the daily volume-weighted average price per share of Assertio common stock calculated based on the ten (10) consecutive trading days ending two trading days prior to the date of the Merger Agreement (i.e., $6.04 per share) and (ii) a number of CVRs equal to the number of shares of Spectrum common stock underlying such Spectrum Stock Option.

•

With respect to any Spectrum Stock Options with an exercise price per share of Spectrum common stock that is equal to or greater than the value of the Upfront Merger Consideration and less than the sum of the Upfront Consideration and the maximum amount payable under a CVR (each, a “Contingent In-the-Money Stock Option”), converted into the right to receive a number of CVRs equal the number of shares of Spectrum common stock underlying such Spectrum Stock Option; provided, however, that the payment, if any, under each CVR will be reduced by the amount by which the exercise price per share exceeds the value of the Upfront Merger Consideration; provided, further that, for the avoidance of doubt, such Contingent In-the-Money Stock Option will not entitle the holder thereof to receive any shares of Assertio common stock, cash or other consideration in connection with the effective time.

•

With respect to any Spectrum Stock Options with an exercise price per share of Spectrum common stock that is equal to or greater than the value of the Merger Consideration (each, an “Underwater Spectrum Stock Option”), the holder of such Underwater Spectrum Stock Option will receive no consideration and, effective as of immediately prior to the effective time, will have no further rights thereto.

Treatment of Spectrum RSUs

As of the effective time, each unvested restricted stock unit constituting the right to be issued a share of Spectrum common stock upon vesting granted under Spectrum’s equity incentive plans (each, a “Spectrum RSU”) that is outstanding immediately prior to the effective time will become fully vested, and the holder of such Spectrum RSUs will, automatically and without any required action on the part of the holder thereof or Spectrum, receive the Merger Consideration.

Treatment of Unvested Spectrum RSAs

At the effective time, each share of Spectrum common stock covered by an unvested restricted stock award (“RSA Shares”) granted under Spectrum’s equity incentive plans that is outstanding immediately prior to the effective time will, automatically and without any required action on the part of the holder thereof or Spectrum, become fully vested and be treated like all other shares of Spectrum common stock.

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Treatment of Spectrum SARs

At the effective time, each stock appreciation right with respect to shares of Spectrum common stock (each, a “Spectrum SAR”) granted under Spectrum equity incentive plans that is outstanding as of immediately prior to the effective time, will, if unvested, become vested, and automatically and without any required action on the part of the holder or Spectrum be cancelled and:

•

With respect to any Spectrum SARs with an exercise price per share that is less than the value of the Upfront Merger Consideration (each such Spectrum SAR, an “In-the-Money SAR”), converted into the right to receive (i) a number of shares of Assertio common stock, subject to certain terms with respect to fractional shares and any applicable withholdings, that is equal to the quotient of (A) the product of (x) the total number of shares of Spectrum common stock underlying the Spectrum SAR multiplied by (y) the excess, if any, of the value of the Upfront Merger Consideration over the exercise price of such Spectrum SAR, divided by (B) the average of the daily volume-weighted average price per share of Assertio common stock calculated based on the ten consecutive trading days ending two trading days prior to the date of the Merger Agreement (i.e., $6.04 per share) and (ii) a number of CVRs equal to the number of shares of Spectrum common stock underlying such Spectrum SAR.

•

With respect to any Spectrum SARs with an exercise price per share that is equal to or greater than the value of the Upfront Merger Consideration and less than the sum of the Upfront Merger Consideration and the maximum amount payable under a CVR (each, a “Contingent In-the-Money SAR”), converted into the right to receive a number of CVRs equal the number of shares of Spectrum common stock underlying such Spectrum SAR; provided, however, that the payment, if any, under each CVR will be reduced by the amount by which the exercise price per share exceeds the value of the Upfront Merger Consideration; provided, further that, for the avoidance of doubt, such Contingent In-the-Money SAR will not entitle the holder thereof to receive any shares of Assertio common stock, cash or other consideration in connection with the effective time.

•

With respect to any Spectrum SAR with an exercise price per share that is equal to or greater than the value of the Merger Consideration (each, an “Underwater Spectrum SAR”), the holder of such Underwater Spectrum SAR will receive no consideration and, effective as of immediately prior to the effective time, will have no further rights thereto.

As of the date hereof, all Spectrum SARs are Underwater Spectrum SARs and will be treated in accordance with the above.

Treatment of the Spectrum ESPP

With respect to any offering period under the Spectrum Employee Stock Purchase Plan (the “Spectrum ESPP”) as in effect on the date of the Merger Agreement, no Spectrum employee who is not already a participant in the Spectrum ESPP as of such date may become a participant in the Spectrum ESPP and no participating employee may increase the percentage of his or her payroll deduction election in effect as of the current Spectrum ESPP offering period. Upon consummation of the Merger, the Spectrum ESPP will terminate immediately. As soon as practicable following the date of the Merger Agreement, the ESPP will be suspended and no new offering period will be commenced under the Spectrum ESPP prior to the termination of the Merger Agreement. Prior to the effective time and if any Spectrum ESPP offering period is then in effect, the last day of such offering period will be accelerated to a date before the Closing Date, as determined by the Spectrum board of directors (or relevant committee thereof) in its discretion, and the final settlement or purchase of Spectrum common stock thereunder will be made on that day.

Certain Actions

Prior to the effective time, Spectrum will adopt such resolutions and take all other actions (including, as applicable, providing advance notice to holders of Spectrum Stock Options and Spectrum SARs) to effectuate the treatment of the Spectrum Stock Options, Spectrum SARs, Spectrum RSUs, RSA Shares and the Spectrum ESPP described above.

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Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger (Page 83)

The Assertio board of directors unanimously recommends that you vote “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal. For a description of some of the factors considered by the Assertio board of directors in reaching its decision to approve the Merger Agreement and the transactions contemplated thereby, including the Merger and the share issuance, and additional information on the recommendation of the Assertio board of directors, see “The Merger — Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger.”

Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger (Page 86)

The Spectrum board of directors has (i) determined that the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement are fair and in the best interest of, and are advisable to, Spectrum and the Spectrum stockholders, (ii) approved and adopted the Merger Agreement and approved the Merger and the other transactions contemplated by the Merger Agreement and (iii) recommended that the Spectrum stockholders approve the Merger Agreement. The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal, and “FOR” the Spectrum adjournment proposal. For additional information on the factors considered by the Spectrum board of directors in reaching this decision and the recommendation of the Spectrum board of directors, please see the section titled “The Merger — Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger” beginning on page 86 of this joint proxy statement/prospectus.

Opinions of Assertio’s Financial Advisors

Opinion of SVB Securities LLC (Page 91; Annex C)

Assertio retained SVB Securities as its financial advisor in connection with the merger and the other transactions contemplated by the Merger Agreement, which are referred to in this section, collectively, as the “Transaction”. In connection with this engagement, Assertio requested that SVB Securities evaluate the fairness, from a financial point of view, to Assertio of the Merger Consideration. On April 24, 2023, SVB Securities rendered to the Assertio board of directors its oral opinion, which was subsequently confirmed by delivery of a written opinion dated April 24, 2023 that, as of such date and based upon and subject to the various assumptions, qualifications and limitations upon the review undertaken by SVB Securities in preparing its opinion, the Merger Consideration provided for in the Merger Agreement was fair, from a financial point of view, to Assertio.

The full text of SVB Securities’ written opinion, dated April 24, 2023, which describes the assumptions made and limitations upon the review undertaken by SVB Securities in preparing its opinion, is attached as Annex C and is incorporated herein by reference. SVB Securities’ financial advisory services and opinion were provided for the information and assistance of the Assertio board of directors (in their capacity as directors and not in any other capacity) in connection with and for purposes of its consideration of the Transaction and SVB Securities’ opinion addressed only the fairness, from a financial point of view, as of the date thereof, to Assertio of the Merger Consideration proposed to be paid by Assertio pursuant to the terms of the Merger Agreement. SVB Securities’ opinion did not address any other term or aspect of the Merger Agreement or the Transaction and does not constitute a recommendation to any stockholder of Assertio or Spectrum as to whether or how such holder should vote with respect to the Merger or otherwise act with respect to the Transaction or any other matter. See “The Merger — Opinions of Assertio’s Financial Advisors — Opinion of SVB Securities LLC.”

The full text of SVB Securities’ written opinion should be read carefully in its entirety for a description of the assumptions made and limitations upon the review undertaken by SVB Securities in preparing its opinion.

Opinion of H.C. Wainwright & Co., LLC (Page 99; Annex D)

Assertio retained Wainwright to provide it with a fairness opinion in connection with the Merger. The Assertio board of directors selected Wainwright to act as Assertio’s financial advisor based on Wainwright’s qualifications, expertise and reputation, and its knowledge and understanding of Assertio’s business and

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affairs. At a meeting of the Assertio board of directors, Wainwright rendered its oral opinion, subsequently confirmed in Wainwright’s written opinion dated as of April 24, 2023, to the effect that, as of the date of Wainwright’s written opinion, and based upon and subject to the factors and assumptions and qualifications set forth in Wainwright’s written opinion, the consideration to be paid pursuant to the Merger Agreement, consisting of the Merger Consideration, was fair from a financial point of view to Assertio.

The full text of the written opinion of Wainwright, dated April 24, 2023, which sets forth the assumptions made, procedures followed, matters considered, qualifications and limitations on the review undertaken in connection with Wainwright’s opinion, is attached to this proxy statement/prospectus as Annex D. The summary of Wainwright’s opinion contained in this proxy statement/prospectus is qualified in its entirety by reference to the full text of Wainwright’s written opinion. Wainwright’s opinion was provided for the information and assistance of the Assertio board of directors in connection with its consideration of the Merger. The opinion does not constitute a recommendation to the Assertio board of directors, Assertio, any security holder or any other party as to how to act or vote or make any election with respect to any matter relating to the Merger, including the Assertio share issuance proposal in the case of Assertio, and the Spectrum merger proposal in the case of Spectrum, or otherwise. Wainwright’s opinion was approved by a fairness committee of Wainwright. See “The Merger — Opinions of Assertio’s Financial Advisors — Opinion of H.C. Wainwright & Co., LLC.”

Opinion of Spectrum’s Financial Advisor

Opinion of Guggenheim Securities, LLC (Page 105; Annex E)

Spectrum retained Guggenheim Securities, LLC (“Guggenheim Securities”) as its financial advisor in connection with the potential sale of, merger with, or another extraordinary corporate transaction involving Spectrum. In connection with the Merger, Guggenheim Securities rendered an opinion to Spectrum’s Board of Directors (the “Spectrum Board”) to the effect that, as of April 24, 2023 and based on and subject to the matters considered, the procedures followed, the assumptions made and various limitations of and qualifications to the review undertaken, the exchange ratio and the CVR consideration was fair, from a financial point of view, to the stockholders of Spectrum. The full text of Guggenheim Securities’ written opinion, which is attached as Annex E to this joint proxy statement/prospectus and which you should read carefully and in its entirety, is subject to the assumptions, limitations, qualifications and other conditions contained in such opinion and necessarily based on economic, capital markets and other conditions, and the information made available to Guggenheim Securities, as of the date of such opinion.

Guggenheim Securities’ opinion was provided to the Spectrum Board (in its capacity as such) for its information and assistance in connection with its evaluation of the exchange ratio and CVR consideration (taken together). Guggenheim Securities’ opinion and any materials provided in connection therewith do not constitute a recommendation to the Spectrum Board with respect to the Merger, nor does Guggenheim Securities’ opinion or the summary of its underlying financial analyses elsewhere in this joint proxy statement/prospectus constitute advice or a recommendation to any holder of Spectrum common stock as to how to vote or act in connection with the Merger or otherwise. Guggenheim Securities’ opinion does not address Spectrum’s underlying business or financial decision to pursue or effect the Merger, the relative merits of the Merger as compared to any alternative business or financial strategies that might exist for Spectrum, any refinancing related to the Merger or the effects of any other transaction in which Spectrum might engage. Guggenheim Securities’ opinion addressed only the fairness, from a financial point of view and as of the date of such opinion, of the exchange ratio and CVR consideration (taken together) to the stockholders of Spectrum and did not express any view or opinion as to (i) any other term, aspect or implication of (a) the Merger (including, without limitation, the form or structure of the Merger) or the Merger Agreement or (b) any other agreement, transaction document or instrument contemplated by the Merger Agreement or to be entered into or amended in connection with the Merger (including, without limitation, the CVR Agreement), (ii) the likelihood or probability of the achievement or satisfaction of the net sales thresholds necessary for the CVR consideration to be paid in accordance with the Merger Agreement and the CVR Agreement or (iii) the fairness, financial or otherwise, of the Merger to, or of any consideration to be paid to or received by, the holders of any class of securities, creditors or other constituencies of Assertio or Spectrum. Furthermore, Guggenheim Securities did not express any view or opinion as to the fairness, financial or otherwise, of the amount or nature of any compensation payable to or to be received by any of Assertio’s or Spectrum’s directors, officers or employees,

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or any class of such persons, in connection with the Merger relative to the exchange ratio and CVR consideration (taken together) or otherwise.

For a description of the opinion that the Spectrum Board received from Guggenheim Securities, see “The Merger — Opinion of Spectrum’s Financial Advisor — Opinion of Guggenheim Securities, LLC” beginning on page 105.

The Assertio Special Meeting (Page 51)

To permit stockholder attendance and participation, while protecting the health and safety of Assertio’s stockholders, board of directors and management team, the Assertio special meeting will be held solely in a virtual meeting format via live webcast on July 27, 2023, beginning at 12:30 p.m., Central Time. Assertio stockholders will be able to virtually attend and vote at the Assertio special meeting by visiting the Assertio special meeting website at www.cstproxy.com/assertiotx/sm2023.

The purposes of the Assertio special meeting are as follows:

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Assertio Proposal 1: Approval of the Share Issuance. To consider and vote on the Assertio share issuance proposal; and

•

Assertio Proposal 2: Adjournment of the Assertio Special Meeting. To consider and vote on the Assertio adjournment proposal.

Completion of the Merger is conditioned on the approval of the Assertio share issuance proposal (Assertio Proposal 1) by Assertio stockholders.

Only holders of record of shares of Assertio common stock outstanding as of the close of business on June 13, 2023 (the “Assertio record date”) are entitled to notice of, and to vote at, the Assertio special meeting or any adjournment or postponement thereof. Assertio stockholders may cast one vote for each share of Assertio common stock that they own of record as of the Assertio record date.

A quorum of Assertio stockholders is necessary to hold the Assertio special meeting. A quorum will exist at the Assertio special meeting if holders of record of shares of Assertio common stock representing a 331∕3% of the issued and outstanding shares of Assertio common stock entitled to vote at the Assertio special meeting are virtually present via the Assertio special meeting website or represented by proxy. All shares of Assertio common stock represented by a valid proxy and all abstentions will be counted as present for purposes of establishing a quorum. All of the proposals for consideration at the Assertio special meeting are considered “non-routine” matters under Nasdaq SM rules, and, therefore, brokers are not permitted to vote on any of the matters to be considered at the Assertio special meeting unless they have received instructions from the beneficial owners. As a result, no “broker non-votes” are expected at the Assertio special meeting, and shares held in “street name” will not be counted as present for the purpose of determining the existence of a quorum unless the Assertio stockholder provides their bank, broker or other nominee with voting instructions for at least one of the proposals brought before the Assertio special meeting.

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voting power will deemed to be withheld with respect to the Assertio share issuance proposal and such failure to provide voting instructions will have no effect on the Assertio share issuance proposal.

Whether or not a quorum is present at the Assertio special meeting, approval of the Assertio adjournment proposal requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal. Accordingly, any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio adjournment proposal. An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote on the Assertio adjournment proposal to vote at the Assertio special meeting on the Assertio adjournment proposal will have the same effect as a vote “AGAINST” the Assertio adjournment proposal. However, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio adjournment proposal, voting power will deemed to be withheld with respect to the Assertio adjournment proposal and such failure to provide voting instructions will have no effect on the Assertio adjournment proposal.

The Spectrum Special Meeting (Page 60)

The Spectrum special meeting will be held virtually at www.meetnow.global/MYXFZTA on July 27, 2023, at 10:00 a.m., Eastern Time. The Spectrum special meeting is being held to consider and vote on the following proposals:

the Spectrum merger proposal;

the Spectrum advisory compensation proposal; and

the Spectrum adjournment proposal.

Consummation of the Merger is conditioned on, among other things, obtaining approval of the Spectrum merger proposal. Approval of the Spectrum adjournment proposal and the Spectrum advisory compensation proposal are not conditions to the obligations of Spectrum, Assertio or Merger Sub to consummate the Merger.

Only holders of record of outstanding shares of Spectrum common stock as of the Spectrum record date are entitled to notice of, and to vote at, the Spectrum special meeting or any adjournment or postponement of the Spectrum special meeting. Each Spectrum stockholder is entitled to one vote for each share of Spectrum common stock that is outstanding in his, her or its name on Spectrum’s books as of close of business on the Spectrum record date for each proposal.

If holders of record of 331∕3% of the issued and outstanding shares of Spectrum common stock as of the Spectrum record date entitled to vote at the Spectrum special meeting are present in person or represented by proxy at the Spectrum special meeting (for purposes of the Spectrum special meeting, a “quorum”), approval of the Spectrum merger proposal requires the affirmative vote of holders of a majority of the outstanding shares of Spectrum common stock entitled to vote on the proposal. Accordingly, the failure of a Spectrum stockholder to vote on the Spectrum merger proposal (including the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give any voting instructions to that bank, broker, trustee or other nominee) or the failure of a Spectrum stockholder to attend the Spectrum special meeting, in person or represented by proxy will have the same effect as a vote “AGAINST” the Spectrum merger proposal.

If a quorum is present at the Spectrum special meeting, approval of the Spectrum advisory compensation proposal and the Spectrum adjournment proposal each requires the affirmative vote of the holders of a majority of the shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting. Accordingly, the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give voting instructions to its bank, broker, trustee or other nominee on the Spectrum advisory compensation proposal or the Spectrum

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adjournment proposal will have no effect on the Spectrum advisory compensation proposal or Spectrum adjournment proposal, respectively, regardless of whether such stockholder gives voting instructions on other proposals.

All abstentions from voting will have the same effect as a vote “AGAINST” each of the Spectrum merger proposal, the Spectrum advisory compensation proposal and the Spectrum adjournment proposal.

Assuming a quorum is present, the failure of record owners who are not present in person or represented by proxy at the Spectrum special meeting to vote will have no effect on the outcome of a vote on either of the Spectrum advisory compensation proposal or the Spectrum adjournment proposal.

The chairperson of the meeting will have the right and authority to recess and/or adjourn the Spectrum special meeting and, if a quorum is not present at the Spectrum special meeting, Spectrum stockholders holding a majority in voting power of shares of Spectrum capital stock, present in person or by proxy and entitled to vote thereat, will have the power to adjourn the meeting (subject to certain restrictions in the Merger Agreement, including that adjournment, without Assertio’s consent, must be more than five but less than 20 days after the date on which the Spectrum special meeting was originally scheduled).

Virtual attendance by stockholders of record at the Spectrum special meeting will constitute presence in person for the purpose of determining the presence of a quorum for the transaction of business at the Spectrum special meeting.

Interests of Assertio’s Directors and Executive Officers in the Merger (Page 167)

Interests of Spectrum’s Directors and Executive Officers in the Merger (Page 168)

In considering the recommendations of the Spectrum board of directors, Spectrum stockholders should be aware that Spectrum’s directors and executive officers have interests in the Merger that are different from, or in addition to, the interests of other Spectrum stockholders generally. The Spectrum board of directors was aware of and considered these interests, among other matters, in evaluating the Merger Agreement and the Merger, in approving the Merger Agreement and in recommending the applicable Merger-related proposals.

These interests include:

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the executive officers of Spectrum have arrangements with Spectrum that provide for certain severance payments or benefits, accelerated vesting of certain equity-based awards and other rights and other payments or benefits in the event of a qualifying termination of employment following the consummation of the Merger;

•

the Spectrum directors have arrangements with Spectrum that provide for accelerated vesting of certain equity-based awards in the event of a qualifying termination of services following the consummation of the Merger;

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executive officers and directors of Spectrum have rights to indemnification, advancement of expenses and directors’ and officers’ liability insurance that will survive the consummation of the Merger;

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one of the beneficial owners of Spectrum, in connection with the acquisition of Spectrum common stock, entered into an agreement where the beneficial owner has the right to appoint a designee to the Spectrum board of directors, so long as it beneficially owns at least 5% of the Spectrum common stock (which designation right is expected to cease in connection with the consummation of the proposed transaction, after which such owner is expected to own less than 5% of Assertio common stock); and

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•

one current Spectrum director will join the board of directors of the combined company following the closing (as defined in the section titled “The Merger Agreement — Closing and Effective Time of the Merger” beginning on page 122 of this joint proxy statement/prospectus).

The Spectrum board of directors was aware of these additional interests of Spectrum’s directors and executive officers and considered these potential interests, among other matters, in evaluating and negotiating the Merger Agreement and the Merger, in approving the Merger Agreement and in recommending the applicable Merger-related proposals. For a further discussion of the interests of Spectrum’s directors and executive officers in the Merger, see the section titled “Interests of Spectrum’s Directors and Executive Officers in the Merger” on page 168 of this joint proxy statement/prospectus.

Governance of the Combined Company (Page 133)

Assertio has agreed to appoint one member of the Spectrum board of directors to the Assertio board of directors as of the effective time, with such director to hold office until the earliest to occur of the appointment or election and qualification of his or her successor or his or her death, resignation, disqualification or proper removal. Such director must qualify as an “independent director” under applicable Nasdaq SM rules and regulations, will be nominated by Spectrum and will be selected and designated by the Assertio board of directors upon the Assertio board of director’s consent (such consent not to be unreasonably withheld, conditioned or delayed). Assertio has agreed not to propose to remove such director other than for cause during the 12-month period following the closing date.

Daniel Peisert will lead the combined company as Chief Executive Officer.

Organizational Documents and Directors and Officers of the Surviving Corporation (Page 133)

At the effective time, Spectrum’s certificate of incorporation will be amended and restated in its entirety to read as the certificate of incorporation of Merger Sub. The parties to the Merger Agreement will also take all requisite actions to amend the bylaws of Spectrum to conform to the bylaws of Merger Sub except that the name of the surviving corporation will be “Spectrum Pharmaceuticals, Inc.” Merger Sub’s directors and officers immediately prior to the effective time will become the initial directors and officers of Spectrum as the surviving corporation.

Certain Beneficial Owners of Assertio Common Stock (Page 194)

At the close of business on June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, Assertio directors and executive officers and their affiliates, as a group, owned and were entitled to vote approximately 2.8% of the shares of Assertio common stock outstanding on such date. Although none of them has entered into any agreement obligating them to do so, Assertio currently expects that all Assertio directors and executive officers will vote their shares “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal. For more information regarding the security ownership of Assertio directors and executive officers, see “Certain Beneficial Owners of Assertio Common Stock — Security Ownership of Assertio Directors and Executive Officers.”

Certain Beneficial Owners of Spectrum Common Stock (Page 196)

At the close of business on June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, Spectrum’s directors and executive officers and their affiliates, as a group, beneficially owned and were entitled to vote approximately 1,205,752 shares of Spectrum common stock, collectively representing 0.6% of the shares of Spectrum common stock outstanding on that date. Spectrum currently expects that all of its directors and executive officers, other than Juhyun Lim and the shares of Spectrum common stock beneficially owned by Hanmi Pharmaceutical Co., Ltd. (“Hanmi”), will vote their shares “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal (if necessary). Ms. Lim and Hanmi are expected to abstain.

For more information regarding the security ownership of Spectrum directors and executive officers, please see the section titled “Certain Beneficial Owners of Spectrum Common Stock” beginning on page 196 of this joint proxy statement/prospectus.

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Regulatory Approvals (Page 143)

Assertio, Merger Sub and Spectrum have each agreed to cooperate with each other and to use (and to cause their subsidiaries to use) reasonable best efforts to take, or cause to be taken, all actions, and to do, or cause to be done, and cooperate with each other in order to do, all things necessary, proper or advisable to cause the conditions to the closing to be satisfied as promptly as practicable (and in any event no later than the Termination Date) and to consummate and make effective the transactions contemplated by the Merger Agreement, including to obtain all required regulatory approvals as promptly as practicable, subject to certain limits. See “The Merger — Regulatory Approvals.”

The obligations of Assertio and Spectrum to consummate the Merger are subject to, among other conditions, the termination or expiration of any waiting period (or any extension thereof) applicable to the transactions contemplated by the Merger Agreement under the HSR Act, which will occur as of 11:59 p.m., Eastern Time, on June 7, 2023.

Ownership of the Combined Company (Page 123)

Based on the number of shares of Assertio and Spectrum common stock outstanding as of June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, upon completion of the Merger (without consideration of the shares of Assertio common stock underlying the CVRs), former Spectrum stockholders are expected to own approximately 35% of the outstanding shares of Assertio common stock and Assertio stockholders immediately prior to the Merger are expected to own approximately 65% of the outstanding shares of Assertio common stock. The relative ownership interests of Assertio stockholders and former Spectrum stockholders in the combined company immediately following the Merger will depend on the number of shares of Assertio and Spectrum common stock issued and outstanding immediately prior to the Merger.

Appraisal Rights (Page 188)

If the Merger is completed, holders of shares of Spectrum stockholders who do not vote in favor of the adoption of the Merger Agreement and who properly demand an appraisal of their shares and who otherwise comply with the requirements set forth in Section 262 of the DGCL will be entitled to appraisal rights in connection with the Merger. Strict compliance with the statutory procedures in Section 262 of the DGCL is required. Failure to timely and properly comply with such statutory requirements will result in the loss of your appraisal rights. The relevant provisions of the DGCL are included as Annex F to this proxy statement/prospectus.

You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising your appraisal rights, Spectrum stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel. Failure to strictly comply with these provisions will result in the loss of appraisal rights. See the section titled “Appraisal Rights” starting on page 188 for additional information, and the text of Section 262 of the DGCL reproduced in its entirety as Annex F to this proxy statement/prospectus.

Conditions to the Completion of the Merger (Page 146)

The obligations of each of Assertio and Spectrum to complete the Merger are subject to the satisfaction or waiver, in whole or in part (to the extent permitted by applicable law), at or prior to the closing, of each of the following conditions:

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approval by Spectrum stockholders of the Spectrum merger proposal;

•

approval by Assertio stockholders of the Assertio share issuance proposal;

•

no restraining orders, injunctions or other judgments, orders or decrees issued by any court of competent jurisdiction or other legal restraints or prohibitions, or any law enacted, entered, promulgated or enforced by any governmental entity that, in any case, remains in effect and prevents, prohibits or makes illegal the consummation of the Merger or the other transactions contemplated by the Merger Agreement;

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•

the termination or expiration of any applicable waiting period (or extension thereof) under the HSR Act;

•

the approval for listing by Nasdaq SM of the shares of Assertio common stock to be issued to Spectrum stockholders in the Merger, subject to official notice of issuance;

•

the execution of the CVR Agreement by Assertio and the Rights Agent and its continued effectiveness; and

•

the effectiveness of the registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part registering the Assertio common stock issuable pursuant to the Merger Agreement and the absence of any stop order or proceedings (commenced or threatened in writing by the SEC) with respect thereto.

In addition, each party’s obligation to complete the Merger is subject to, among other things, the accuracy of certain representations and warranties of the other party and the compliance by such other party with certain of its covenants, in each case, subject to the materiality standards set forth in the Merger Agreement, and the absence of the occurrence of any material adverse effect. Additionally, Spectrum’s obligation to complete the Merger is also subject to its receipt of an opinion, delivered by Gibson, Dunn & Crutcher LLP or another nationally recognized tax counsel acceptable to Assertio and Spectrum, that the Merger will qualify as a “reorganization” within the meaning of Section 368(a) of the Code.

Neither Assertio nor Spectrum can be certain when, or if, the conditions to the Merger will be satisfied or waived, or that the Merger will be completed.

No Solicitation of Acquisition Proposals (Page 138)

As more fully described under “The Merger Agreement — No Solicitation of Acquisition Proposals,” subject to the exceptions summarized below, Assertio and Spectrum have each agreed that they will not (a) initiate, solicit, knowingly assist, knowingly induce or knowingly encourage or facilitate (including by providing information) any inquiries, proposals or offers with respect to, or the making, submission, announcement or completion of, any proposal or offer that constitutes, or would be reasonably expected to lead to, an acquisition proposal (as defined under “The Merger Agreement — No Solicitation of Acquisition Proposals”), (b) engage in, continue or participate in any discussions or negotiations with any person (other than Assertio or Spectrum and each of their respective affiliates and representatives, as applicable) concerning any acquisition proposal or any inquiry, proposal or offer that would reasonably be expected to lead to any acquisition proposal, (c) furnish or provide or cause to be furnished or provided any non-public information or data relating to Assertio or Spectrum or their respective subsidiaries, as applicable, in connection with, or for the purpose of soliciting, initiating, encouraging or facilitating, or in response to, any inquiry, proposal or offer that constitutes or would reasonably be expected to lead to an acquisition proposal, or (d) resolve or agree to do any of the foregoing.

Notwithstanding the restrictions described above, if at any time prior to obtaining approval of the Spectrum merger proposal, in the case of Spectrum, or the Assertio share issuance proposal, in the case of Assertio, Assertio or Spectrum, as applicable, receives an unsolicited bona fide, written acquisition proposal from a third party after the date of the Merger Agreement that did not result from a material breach of the non-solicitation provisions in the Merger Agreement and that the Assertio or Spectrum board of directors, as applicable, determines in good faith (after consultation with its outside legal counsel and financial advisor) constitutes or would reasonably be expected to lead to a superior proposal (as defined under “The Merger Agreement — No Solicitation of Acquisition Proposals”) and that failure to engage in such discussions or negotiations, or provide such information, would reasonably be expected to be inconsistent with such board of directors’ fiduciary duties to such party and its stockholders under applicable legal requirements, Assertio or Spectrum, as applicable, may (a) furnish information with respect to Assertio or Spectrum, as applicable, to the party making the acquisition proposal, and (b) participate in discussions or negotiations with the party making the acquisition proposal, in either case, subject to certain conditions and obligations in the Merger Agreement.

Assertio and Spectrum have also agreed to notify the other (a) promptly following (and in any event, within 24 hours of the receipt of) any acquisition proposal and (b) to keep the other party reasonably

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informed on a current basis (and in any event, within 24 hours) as to the status of any acquisition proposal, including informing the other party of any material change to such acquisition proposal’s terms, the status of any negotiations, and any change in its intentions.

No Change of Recommendation (Page 140)

The Merger Agreement provides that, among other restrictions and subject to certain exceptions, neither the Assertio nor Spectrum board of directors, nor any committee thereof, will (a) withdraw, change, qualify, withhold, amend or modify in a manner adverse the other party (or publicly propose to do so), the Assertio board of directors’ recommendation to Assertio stockholders to approve the share issuance or the Spectrum board of directors’ recommendation to Spectrum stockholders to adopt the Merger Agreement, as applicable, or (b) adopt, approve or recommend (or publicly propose to do so) any acquisition proposal.

Notwithstanding the restrictions described above, at any time prior to obtaining the approval by Assertio stockholders of the Assertio share issuance proposal or by Spectrum stockholders of the Spectrum merger proposal, as the case may be, the Assertio or Spectrum board of directors, as applicable, may make a change of recommendation and/or terminate the Merger Agreement to concurrently enter into a definitive agreement with respect to an acquisition proposal if it determines in good faith (after consultation with its outside legal counsel and financial advisor) that such acquisition proposal is a superior proposal and that failure to take such action with respect to such acquisition proposal would reasonably be expected to be inconsistent with the such board of directors’ fiduciary duties to such party and its stockholders under applicable legal requirements (and subject to compliance with certain obligations set forth in the Merger Agreement, including providing the other party with prior notice and the opportunity to negotiate for a period to match the terms of the superior proposal and payment of the applicable termination fee concurrent with any such termination of the Merger Agreement).

In addition, the Assertio or Spectrum board of directors, as the case may be, is permitted under certain circumstances, prior to obtaining stockholder approval of the Assertio share issuance proposal, in the case of Assertio, or the Spectrum merger proposal, in the case of Spectrum, and subject to compliance with certain obligations set forth in the Merger Agreement (including providing the other party with prior notice and the opportunity to negotiate during such notice period to amend the terms of the Merger Agreement) to make a change of recommendation in response to an intervening event (unrelated to an acquisition proposal) if the Assertio or Spectrum board of directors, as applicable, determines in good faith (after consultation with its outside legal counsel and financial advisor) that the failure to do so would be reasonably likely to be inconsistent with its fiduciary duties.

Termination of the Merger Agreement (Page 148)

The Merger Agreement may be terminated and the Merger abandoned:

•

by mutual written consent of Assertio and Spectrum at any time prior to the effective time;

•

by either party, if the Merger has not been consummated on or prior to the Termination Date, including any automatic extensions thereof (however, a party may not terminate the Merger Agreement if such party’s material breach of any of its obligations under the Merger Agreement materially contributed to the failure of the closing to have occurred by the Termination Date);

•

by either party, if a governmental authority of competent jurisdiction issues a final and non-appealable order or adopts or enacts a law that is final and non-appealable that permanently prevents, enjoins or makes illegal the consummation of the Merger (however, a party may not terminate the Merger Agreement if such party has (i) not used reasonable best efforts to contest, appeal and remove such restraint or (ii) failed in any material respect to comply with any of its obligations under the Merger Agreement with respect to obtaining regulatory approvals);

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by either party, if the other party has made a change of recommendation, prior to the other party obtaining its required stockholder approval;

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by either party, if either the Spectrum merger proposal or the Assertio share issuance proposal is not approved at the Spectrum special meeting or the Assertio special meeting, respectively, including any postponement or adjournment thereof;

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by either party, if prior to obtaining such party’s stockholder approval, (a) such party’s board of directors shall have authorized the party to enter into a definitive agreement relating to a superior proposal and (b) concurrently with the termination of the Merger Agreement, such party enters into the definitive agreement relating to a superior proposal and pays the other party the applicable termination fee pursuant to the Merger Agreement; or

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by either party, if the other party breaches or fails to perform any its representations, warranties, covenants or agreements in the Merger Agreement and such breach or failure to perform (a) would result in the failure of certain conditions to closing and (b) is not curable by the Termination Date or, if curable, is not cured by the date that is 30 days following written notice describing such breach (however, the terminating party may not exercise this termination right if it is then in breach of any covenant or agreement contained in the Merger Agreement which breach would give rise to the failure of a condition to the Merger Agreement regarding accuracy of representations and warranties and compliance with covenants).

Termination Fees (Page 149)

Each party has agreed to pay a termination fee to the other party equal to $8,300,000, less the amount of previously paid expenses, if any, if the Merger Agreement is terminated in certain circumstances, including if the board of directors of such party authorizes entry into a definitive agreement relating to a superior proposal. If the Merger Agreement is terminated by either party due to the other party’s failure to receive the requisite approval of its stockholders, then the party that failed to obtain such approval will be required to reimburse the other party for up to $1,000,000 of reasonable and documented out-of-pocket fees and expenses incurred in connection with the transactions contemplated by the Merger Agreement.

Accounting Treatment (Page 124)

Assertio prepares its financial statements in accordance with GAAP. The Merger will be accounted for using the acquisition method of accounting under the provisions of Accounting Standards Codification (“ASC”) 805, Business Combinations, with Assertio representing the accounting acquirer under this guidance. Assertio will record assets acquired, including identifiable intangible assets, and liabilities assumed from Spectrum at their respective fair values at the date of completion of the Merger. Any excess of the purchase price (as described in Note 2 (Basis of Pro Forma Presentation) to the unaudited pro forma condensed combined financial information) over the net fair value of such assets and liabilities will be recorded as goodwill.

The financial condition and results of operations of Assertio after completion of the Merger will reflect Spectrum after completion of the Merger, but will not be restated retroactively to reflect the historical financial condition or results of operations of Spectrum. The earnings of Assertio following completion of the Merger will reflect acquisition accounting adjustments, including the effect of changes in the carrying value for assets and liabilities on amortization expense. Goodwill will not be amortized but will be tested for impairment at least annually, and all tangible and intangible assets including goodwill will be tested for impairment when certain indicators are present. If, in the future, Assertio determines that tangible or intangible assets (including goodwill) are impaired, Assertio would record an impairment charge at that time.

Litigation Relating to the Merger (Page 124)

Following the announcement of the Merger, two purported shareholders of Spectrum filed complaints against Spectrum and each member of the Spectrum board of directors alleging violations of the federal securities laws. The complaints generally allege that Spectrum filed a materially incomplete and misleading Registration Statement on Form S-4 with the SEC and that, as a result, all defendants violated Section 14(a) of the Exchange Act and that each member of the Spectrum board of directors violated Section 20(a) of the Exchange Act. The alleged omissions relate to (i) the sales process leading up to the proposed transaction; (ii) certain financial projections for Spectrum; (iii) certain financial projections for Assertio; (iv) the financial analyses by Guggenheim Securities; (v) the financial analyses by SVB; and (vi) the financial analyses by Wainwright. The complaints seek (i) injunctive relief; (ii) rescission in the event the Merger is

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consummated or alternatively rescissory damages; (iii) a direction that the Spectrum board of directors issue a revised Registration Statement; (iv) plaintiff’s attorneys’ and experts’ fees and costs; and (v) other such relief that the court deems just and proper.

Additional lawsuits related to the Merger may be filed in the future, which could prevent or delay completion of the Merger.

U.S. Federal Income Tax Considerations Relating to the Merger (Page 169)

Assertio and Spectrum intend that, for U.S. federal income tax purposes, the Merger qualifies as a “reorganization” within the meaning of Section 368(a) of the Code (the “Intended Tax Treatment”). It is a condition to Spectrum’s obligation to consummate the Merger that Spectrum receive an opinion, dated as of the closing date, from Gibson, Dunn & Crutcher LLP or such other nationally recognized tax counsel reasonably acceptable to Spectrum and Assertio, to the effect that, on the basis of facts, representations, assumptions and exclusions set forth or referred to in such opinion, the Merger will qualify for the Intended Tax Treatment. Assuming the Merger qualifies for the Intended Tax Treatment, a holder of shares of Spectrum common stock that is subject to U.S. federal income taxation generally, subject to the following sentence, is expected to recognize gain (but not loss) for U.S. federal income tax purposes upon the exchange of such shares for shares of Assertio common stock and the CVRs in the Merger in an amount equal to the lesser of (i) any gain realized with respect to such shares of Spectrum common stock and (ii) the fair market value of the CVRs. The U.S. federal income tax consequences of the Merger are subject to substantial uncertainty, particularly if Milestone Payments are paid in Assertio common stock, in which case it is possible such common stock is treated as additional Assertio common stock received in the Merger which generally would not be taxable upon receipt.

See “U.S. Federal Income Tax Considerations Relating to the Merger” for a more complete description of U.S. federal income tax considerations relating to the Merger for holders of shares of Spectrum common stock. Please consult your tax advisors as to the specific tax consequences of the Merger to you.

Comparison of Stockholders’ Rights (Page 177)

Upon completion of the Merger, Spectrum stockholders receiving shares of Assertio common stock will become Assertio stockholders. The rights of Assertio stockholders will be governed by the DGCL and the Assertio charter and Assertio bylaws in effect at the effective time. As Assertio and Spectrum are both Delaware corporations, the rights of Assertio and Spectrum stockholders are not materially different. However, there are certain differences in the rights of Assertio stockholders under the Assertio charter and Assertio bylaws and of Spectrum stockholders under the Spectrum charter and bylaws. See “Comparison of Stockholders’ Rights.”

Listing of Assertio Common Stock; Delisting and Deregistration of Spectrum Common Stock (Page 125)

It is a condition to the Merger that the shares of Assertio common stock to be issued to Spectrum stockholders in the Merger be approved for listing on Nasdaq SM, subject to official notice of issuance. If the Merger is completed, Spectrum common stock will be delisted from Nasdaq CM and deregistered under the Exchange Act, following which Spectrum will no longer be required to file periodic reports with the SEC with respect to Spectrum common stock.

Spectrum has agreed to cooperate with Assertio prior to the closing to cause the Spectrum common stock to be delisted from Nasdaq CM and be deregistered under the Exchange Act as soon as practicable after the effective time.

Risk Factors (Page 36)

In evaluating the Merger Agreement, the Merger and the share issuance, you should carefully read this joint proxy statement/prospectus and give special consideration to the factors discussed under “Risk Factors.”

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SELECTED UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

The following selected unaudited pro forma condensed combined balance sheet as of March 31, 2023, gives effect to the Merger as if it had occurred on March 31, 2023. The presentation of the unaudited pro forma condensed combined statements of comprehensive income for the three months ended March 31, 2023, and the fiscal year ended December 31, 2022, reflects the combined results of operations as if the Merger had occurred on January 1, 2022. The unaudited pro forma condensed combined financial information is provided for informational purposes only and is not necessarily indicative of results that would have occurred had the Merger been completed as of the dates indicated above. In addition, the unaudited pro forma condensed combined financial information does not purport to be indicative of the future financial position or operating results of the combined operations and does not reflect the costs of any integration activities nor any benefits that may result from realization of future cost savings from operating efficiencies or revenue or other synergies expected to result from the Merger. Future results may vary significantly from the results reflected because of various factors, including those discussed under “Risk Factors.” The selected unaudited pro forma condensed combined financial information should be read together with “Unaudited Pro Forma Condensed Combined Financial Information.”

This unaudited pro forma condensed combined financial information has been prepared to illustrate the estimated effect of the Merger. Such information is based on the following historical consolidated financial statements of Assertio and Spectrum that are incorporated by reference into this joint proxy statement/prospectus, as adjusted to give effect to the Merger:

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Assertio

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Audited historical consolidated financial statements, as included in Assertio’s Annual Report on Form 10-K for the year ended December 31, 2022

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Interim unaudited historical condensed consolidated financial statements, as included in Assertio’s Quarterly Report on Form 10-Q for the three months ended March 31, 2023

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Spectrum

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Audited historical consolidated financial statements, as included in Spectrum’s Annual Report on Form 10-K, as amended, for the year ended December 31, 2022

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Interim unaudited historical condensed consolidated financial statements, as included in Spectrum’s Quarterly Report on Form 10-Q for the three months ended March 31, 2023

For more information regarding such historical consolidated financial statements and related notes, see “Where You Can Find Additional Information.”

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ASSERTIO HOLDINGS, INC.

UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET
AS OF MARCH 31, 2023
(in millions)

	Historical						Transaction Accounting Adjustments			Pro Forma Combined
	Assertio			Spectrum			Transaction Accounting Adjustments			Pro Forma Combined
Cash and cash equivalents and marketable securities		$	69		$	56		$	(29)		$	96
Total assets		$	414		$	108		$	213		$	735
Total debt		$	39		$	29		$	(29)		$	39
Total liabilities		$	164		$	81		$	0		$	245
Total shareholders’ equity		$	251		$	27		$	213		$	491

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ASSERTIO HOLDINGS, INC.

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF
COMPREHENSIVE INCOME
THREE MONTHS ENDED MARCH 31, 2023
(in millions, except per share amounts)

	Historical						Transaction Accounting Adjustments			Pro Forma Combined
	Assertio			Spectrum			Transaction Accounting Adjustments			Pro Forma Combined
Revenues		$	42		$	16		$	—		$	58
Income (loss) from operations		$	5		$	(5)		$	(5)		$	(5)
Net loss and comprehensive loss		$	(3)		$	(5)		$	(3)		$	(11)
Basic net loss per share		$	(0.07)		$	—					$	(0.13)
Diluted net loss per share		$	(0.07)		$	—					$	(0.13)

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ASSERTIO HOLDINGS, INC.

UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF
COMPREHENSIVE INCOME
YEAR ENDED DECEMBER 31, 2022
(in millions, except per share amounts)

	Historical						Transaction Accounting Adjustments			Pro Forma Combined
	Assertio			Spectrum			Transaction Accounting Adjustments			Pro Forma Combined
Revenues		$	156		$	10		$	—		$	166
Income (loss) from operations		$	39		$	(73)		$	(59)		$	(93)
Net income (loss) and comprehensive income (loss)		$	110		$	(78)		$	(44)		$	(12)
Basic net income (loss) per share		$	2.33		$	(0.43)					$	(0.14)
Diluted net income (loss) per share		$	2.03		$	(0.43)					$	(0.14)

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

The registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part, the documents that Assertio and Spectrum refer you to in the registration statement and oral statements made or to be made by Assertio and Spectrum include certain “forward-looking statements” within the meaning of, and subject to the safe harbor created by, Section 27A of the Securities Act, Section 21E of the Exchange Act and the Private Securities Litigation Reform Act of 1995, which are referred to as the “safe harbor provisions.” Statements contained or incorporated by reference in the registration statement of which this joint proxy statement/prospectus forms a part that are not historical facts are forward-looking statements, including statements about the beliefs and expectations of Assertio and Spectrum management relating to the Merger and future financial condition and performance. Words such as “believe,” “continue,” “could,” “expect,” “anticipate,” “intends,” “estimate,” “forecast,” “project,” “should,” “may,” “will,” “would” or the negative thereof and similar expressions are intended to identify such forward-looking statements that are intended to be covered by the safe harbor provisions. Investors are cautioned that any forward-looking statements are subject to known and unknown risks and uncertainties, many of which are beyond the control of both companies, and which may cause actual results and future trends to differ materially from those matters expressed in, or implied or projected by, such forward-looking statements, which speak only as of the date of this joint proxy statement/prospectus. Although these forward-looking statements are based on assumptions that Assertio and Spectrum management, as applicable, believe to be reasonable, they can give no assurance that these expectations will prove to be correct. Investors are cautioned not to place undue reliance on these forward-looking statements. Among the risks and uncertainties that could cause actual results to differ from those described in forward-looking statements are the following:

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the occurrence of any change, event, series of events or circumstances that could give rise to the termination of the Merger Agreement, including a termination of the Merger Agreement under circumstances that could require Assertio to pay a termination fee to Spectrum or require Spectrum to pay a termination fee to Assertio;

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uncertainties related to the timing of the receipt of required regulatory approvals for the Merger and the possibility that Assertio and Spectrum may be required to accept conditions that could reduce or eliminate the anticipated benefits of the Merger as a condition to obtaining regulatory approvals or that the required regulatory approvals might not be obtained at all;

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the price of Assertio and Spectrum common stock could change before the completion of the Merger, including as a result of uncertainty as to the long-term value of the common stock of the combined company or as a result of broader stock market movements;

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the possibility that the parties are unable to complete the Merger due to the failure of Assertio stockholders to approve the share issuance or of Spectrum stockholders to adopt the Merger Agreement, or the failure to satisfy any of the other conditions to the completion of the Merger, or unexpected delays in satisfying any conditions;

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delays in closing, or the failure to close, the Merger for any reason, could negatively impact Assertio, Spectrum or the combined company;

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risks that the pendency or completion of the Merger and the other transactions contemplated by the Merger Agreement disrupt current plans and operations, which may adversely impact Assertio’s or Spectrum’s respective businesses;

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difficulties or delays in integrating the businesses of Assertio and Spectrum following completion of the Merger or fully realizing the anticipated synergies or other benefits expected from the Merger;

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certain restrictions during the pendency of the proposed Merger that may impact the ability of Assertio or Spectrum to pursue certain business opportunities or strategic transactions;

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the nature, cost and outcome of any litigation and other legal proceedings, including any such proceedings related to the proposed Merger and instituted against Assertio, Spectrum, their directors and/or others;

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risks related to the diversion of the attention and time of Assertio or Spectrum management from ongoing business concerns;

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the risk that the proposed Merger or any announcement relating to the proposed Merger could have an adverse effect on the ability of Assertio or Spectrum to retain and hire key personnel or maintain relationships with customers, suppliers, distributors, vendors, strategic partners or other third parties, including regulators and other governmental authorities or agencies, or on Assertio’s or Spectrum’s respective operating results and businesses generally;

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the potentially significant amount of any costs, fees, expenses, impairments or charges related to the Merger;

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the risk that the Milestones pursuant to the CVR Agreement are not achieved;

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the potential dilution of Assertio and Spectrum stockholders’ ownership percentage of the combined company as compared to their ownership percentage of Assertio or Spectrum, as applicable, prior to the Merger;

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the business, economic, political and other conditions in the countries in which Assertio or Spectrum operate;

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events beyond the control of Assertio and Spectrum, such as acts of terrorism, epidemics, pandemics or disease outbreaks, including the continuation or worsening of the COVID-19 pandemic, and changes in applicable law;

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the potential dilution of the combined company’s earnings per share as a result of the Merger;

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Assertio and Spectrum directors and executive officers having interests in the Merger that are different from, or in addition to, the interests of Assertio and Spectrum stockholders generally; and

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the possibility that the combined company’s results of operations, cash flows and financial position after the Merger may differ materially from the unaudited pro forma condensed combined financial information contained in this proxy statement/prospectus.

For further discussion of these and other risks, contingencies and uncertainties applicable to Assertio and Spectrum, their respective businesses and the proposed Merger, see “Risk Factors” in this joint proxy statement/prospectus and in similarly titled sections in Assertio’s and Spectrum’s other filings with the SEC that are incorporated by reference herein. See “Where You Can Find More Information.”

All subsequent written or oral forward-looking statements attributable to Assertio, Spectrum or any person acting on either of their behalf are expressly qualified in their entirety by these cautionary statements. Neither Assertio nor Spectrum is under any obligation to update, alter or otherwise revise any forward-looking statements, whether written or oral, that may be made from time to time, whether as a result of new information, future events or otherwise, and each expressly disclaims any obligation to do so, except as may be required by law.

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RISK FACTORS

In considering how to vote on the proposals to be considered and voted on at the Assertio and Spectrum special meetings, you are urged to carefully consider all of the information contained or incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.” You should also read and consider the risks associated with each of the businesses of Assertio and Spectrum because those risks will affect the combined company. The risks associated with the business of Assertio can be found in Assertio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 and the risks associated with the business of Spectrum can be found in Spectrum’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, as such risks may be updated or supplemented in each company’s subsequently filed Quarterly Reports on Form 10-Q and Current Reports on Form 8-K (excluding any information and exhibits furnished under Item 2.02 or 7.01 thereof), each of which is incorporated by reference in this joint proxy statement/prospectus. In addition, you are urged to carefully consider the following material risks relating to the Merger and the businesses of Assertio, Spectrum and the combined company.

Risks Relating to the Merger

Because the exchange ratio is fixed and will not be adjusted in the event of any change in the price of either Assertio or Spectrum common stock, and because of the uncertainty of the value of, and the ultimate realization on, the CVRs, the value of the consideration that Spectrum stockholders will receive in the Merger is uncertain.

Upon completion of the Merger, each share of Spectrum common stock outstanding immediately prior to the Merger, other than shares held in treasury by Spectrum or held directly by Assertio or Merger Sub, will be converted into the right to receive 0.1783 shares of Assertio common stock (with cash, without interest and less any applicable withholding taxes, in lieu of any fractional shares of Assertio common stock), and one CVR, as described in more detail in the accompanying joint proxy statement/prospectus under the heading “The Merger Agreement — Merger Consideration.” This exchange ratio is fixed in the Merger Agreement and will not be adjusted for changes in the market price of either Assertio or Spectrum common stock prior to the completion of the Merger. The market prices of Assertio and Spectrum common stock have fluctuated prior to and after the date of the announcement of the Merger Agreement and will continue to fluctuate from the date of this joint proxy statement/prospectus to the dates of the Assertio and Spectrum special meetings, and through the date the Merger is consummated. Moreover, the CVRs are non-transferable and there is also uncertainty regarding the value of the CVRs and whether any payment will ultimately be realized on the CVRs, even if the Milestones are satisfied.

Because the value of the Merger Consideration will depend on the market price of Assertio common stock at the time the Merger is completed and the ultimate realization of the CVRs, Spectrum stockholders will not know or be able to determine at the time of the Spectrum special meeting the market value of the Merger Consideration they would receive upon completion of the Merger. Similarly, Assertio stockholders will not know or be able to determine at the time of the Assertio special meeting the market value of the shares of Assertio common stock to be issued pursuant to the Merger Agreement compared to the market value of the shares of Spectrum common stock that are being exchanged in the Merger.

Stock price changes may result from a variety of factors, including, among others, general market and economic conditions, changes in Assertio’s or Spectrum’s respective businesses, operations and prospects, the uncertainty as to the extent of the duration, scope and impact of the COVID-19 pandemic, market assessments of the likelihood that the Merger will be completed, interest rates, general market, industry and economic conditions and other factors generally affecting the respective prices of Assertio and Spectrum common stock, federal, state and local legislation, governmental regulation and legal developments in the industry segments in which Assertio and Spectrum operate, and the timing of the Merger and receipt of required regulatory approvals.

Many of these factors are beyond the control of Assertio and Spectrum, and neither Assertio nor Spectrum is permitted to terminate the Merger Agreement solely due to a decline in the market price of the common stock of the other party. You are urged to obtain current market quotations for Assertio and Spectrum common stock in determining whether to vote in favor of the Assertio share issuance proposal, in the case of Assertio stockholders, or the Spectrum merger proposal, in the case of Spectrum stockholders.

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The market price of Assertio common stock will continue to fluctuate after the Merger.

Upon completion of the Merger, Spectrum stockholders will become holders of Assertio common stock. The market price of the common stock of the combined company will continue to fluctuate, potentially significantly, following completion of the Merger, including for the reasons described above. As a result, former Spectrum stockholders could lose some or all of the value of their investment in Assertio common stock. In addition, any significant price or volume fluctuations in the stock market generally could have a material adverse effect on the market for, or liquidity of, the Assertio common stock received in the Merger, regardless of the combined company’s actual operating performance.

The Merger may not be completed and the Merger Agreement may be terminated in accordance with its terms.

The Merger is subject to a number of conditions that must be satisfied, including the approval by Assertio stockholders of the Assertio share issuance proposal and approval by Spectrum stockholders of the Spectrum merger proposal, or waived (to the extent permitted), in each case prior to the completion of the Merger. These conditions are described under “The Merger Agreement — Conditions to the Completion of the Merger.” These conditions to the completion of the Merger, some of which are beyond the control of Assertio and Spectrum, may not be satisfied or waived in a timely manner or at all, and, accordingly, the Merger may be delayed or not completed.

Additionally, either Assertio or Spectrum may terminate the Merger Agreement under certain circumstances, including, among other reasons, if the Merger is not completed by the Termination Date. In addition, if the Merger Agreement is terminated under specified circumstances, including if the board of directors of Assertio or Spectrum authorizes entry into a definitive agreement relating to a superior proposal, such party will be required to pay a termination fee to the other party equal to $8.3 million, less the amount of previously paid expenses, if any. If the Merger Agreement is terminated under other specified circumstances, including the failure to receive certain required regulatory approvals, then the party that failed to obtain such approval will be required to reimburse the other party for up to $1.0 million of reasonable and documented out-of-pocket fees and expenses incurred in connection with the transaction. See “The Merger Agreement — Termination of the Merger Agreement” and “The Merger Agreement — Termination Fees” for a more complete discussion of the circumstances under which the Merger Agreement could be terminated and when a termination fee may be payable by Assertio or Spectrum.

The termination of the Merger Agreement could negatively impact Assertio or Spectrum and the trading prices of the Assertio or Spectrum common stock.

If the Merger is not completed for any reason, including because Assertio stockholders fail to approve the Assertio share issuance proposal or because Spectrum stockholders fail to approve the Spectrum merger proposal, the ongoing businesses of Assertio and Spectrum may be adversely affected and, without realizing any of the expected benefits of having completed the Merger, Assertio and Spectrum would be subject to a number of risks, including the following:

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each company may experience negative reactions from the financial markets, including negative impacts on its stock price;

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each company may experience negative reactions from its customers, suppliers, distributors and employees;

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each company will be required to pay its respective costs relating to the Merger, such as financial advisory, legal, financing and accounting costs and associated fees and expenses, whether or not the Merger is completed;

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the Merger Agreement places certain restrictions on the conduct of each company’s business prior to completion of the Merger and such restrictions, the waiver of which is subject to the consent of the other company (not to be unreasonably withheld, conditioned or delayed), which may have prevented Assertio and Spectrum from taking actions during the pendency of the Merger that would have been beneficial (see “The Merger Agreement — Conduct of Business Prior to the Merger’s Completion” for a description of the restrictive covenants applicable to Assertio and Spectrum); and

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matters relating to the Merger (including integration planning) will require substantial commitments of time and resources by Assertio and Spectrum management, which could otherwise have been devoted to day-to-day operations or to other opportunities that may have been beneficial to Assertio or Spectrum, as applicable, as an independent company.

The market price for shares of Assertio common stock may be affected by factors different from, or in addition to, those that historically have affected or currently affect the market prices of shares of Assertio or Spectrum common stock.

Upon consummation of the Merger, Assertio stockholders and Spectrum stockholders will both hold shares of common stock in the combined company. Assertio’s businesses differ from those of Spectrum, and Spectrum’s businesses differ from those of Assertio, and, accordingly, the results of operations of the combined company will be affected by some factors that are different from those currently or historically affecting the results of operations of Assertio and Spectrum. The results of operations of the combined company may also be affected by factors different from those that currently affect or have historically affected either Assertio or Spectrum. For a discussion of the businesses of each of Assertio and Spectrum and some important factors to consider in connection with those businesses, see “The Parties to the Merger” and the other information contained or incorporated in this joint proxy statement/prospectus. See “Where You Can Find More Information.”

Based on the number of shares of Spectrum common stock outstanding as of June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, it is expected that Assertio will issue approximately 36.6 million shares of Assertio common stock in the Merger (without consideration of the shares of Assertio common stock underlying the CVRs). Former Spectrum stockholders may decide not to hold the shares of Assertio common stock that they will receive in the Merger, and Assertio stockholders may decide to reduce their investment in Assertio as a result of the changes to Assertio’s investment profile as a result of the Merger. Other Spectrum stockholders, such as funds with limitations on their permitted holdings of stock in individual issuers, may be required to sell the shares of Assertio common stock that they receive in the Merger. Such sales of Assertio common stock could have the effect of depressing the market price for Assertio’s common stock.

The shares of common stock of the combined company to be received by Spectrum stockholders as a result of the Merger will have rights different from the shares of Spectrum common stock.

Upon completion of the Merger, Spectrum stockholders will no longer be stockholders of Spectrum, but will instead become stockholders of Assertio. As Assertio and Spectrum are both Delaware corporations, the rights of Assertio and Spectrum stockholders are not materially different. However, there are certain differences in the rights of Assertio stockholders under Assertio’s amended and restated certificate of incorporation, which is referred to as the “Assertio charter,” and Assertio’s amended and restated bylaws, which are referred to as the “Assertio bylaws,” and of Spectrum stockholders under Spectrum’s restated certificate of incorporation, which is referred to as the “Spectrum charter,” and Spectrum’s third amended and restated bylaws, which are referred to as the “Spectrum bylaws.” See “Comparison of Stockholders’ Rights” for a discussion of these rights.

After the Merger, Spectrum stockholders will have a significantly lower ownership and voting interest in Assertio than they currently have in Spectrum and will exercise less influence over management and policies of the combined company.

Based on the number of shares of Assertio and Spectrum common stock outstanding on June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, upon completion of the Merger (without consideration of the shares of Assertio common stock underlying the CVRs), former Spectrum stockholders are expected to own approximately 35% of the outstanding shares of Assertio common stock (without consideration of any potential shares of Assertio common stock underlying the CVRs) and Assertio stockholders immediately prior to the Merger are expected to own approximately 65% of the outstanding shares of Assertio common stock. Consequently, former Spectrum stockholders will have less influence over the management and policies of the combined company than they currently have over the management and policies of Spectrum.

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Until the completion of the Merger or the termination of the Merger Agreement in accordance with its terms, Assertio and Spectrum are each prohibited from entering into certain transactions and taking certain actions that might otherwise be beneficial to Assertio, Spectrum and/or their respective stockholders.

From and after the date of the Merger Agreement and prior to completion of the Merger, the Merger Agreement restricts Assertio and Spectrum from taking specified actions without the consent of the other party and requires that the business of each company and its respective subsidiaries be conducted in the ordinary course in all material respects. These restrictions may prevent Assertio or Spectrum, as applicable, from taking actions during the pendency of the Merger that would have been beneficial. Adverse effects arising from these restrictions during the pendency of the Merger could be exacerbated by any delays in consummation of the Merger or termination of the Merger Agreement. See “The Merger Agreement — Conduct of Business Prior to the Merger’s Completion.”

Obtaining required approvals and satisfying closing conditions may prevent or delay completion of the Merger.

The Merger is subject to a number of conditions to closing as specified in the Merger Agreement. These closing conditions include, among others, (i) approval by Spectrum stockholders of the Spectrum merger proposal, (ii) approval by Assertio stockholders of the Assertio share issuance proposal, (iii) the absence of restraining orders, injunctions or other judgments, orders or decrees issued by any court of competent jurisdiction or other legal restraints or prohibitions, or any law enacted, entered, promulgated or enforced by any governmental entity that, in any case, remains in effect and prevents, prohibits or makes illegal the consummation of the Merger or the other transactions contemplated by the Merger Agreement, (iv) the expiration or earlier termination of any applicable waiting period (and any extension thereof), under the HSR Act, (v) approval for listing on Nasdaq SM of the shares of Assertio common stock to be issued in connection with the Merger, subject to official notice of issuance, (vi) execution by Assertio and the Rights Agent of the CVR Agreement, which shall be in full force and effect, and (vii) the effectiveness of the registration statement on Form S-4 of which this joint proxy statement/prospectus forms a part registering the Assertio common stock issuable pursuant to the Merger Agreement and the absence of any stop order or proceedings (commenced or threatened in writing by the SEC) with respect thereto. The obligation of each of Assertio and Spectrum to consummate the Merger is also conditioned on, among other things, the truth and accuracy of the representations and warranties made by the other party on the date of the Merger Agreement and on the closing date (subject to certain materiality and material adverse effect qualifiers), the performance by the other party in all material respects of its obligations under the Merger Agreement, and there having been no effect that, individually or in the aggregate, may result in, together with all other effects, has constituted or resulted in, or would reasonably be expected to constitute or result in, a material adverse effect. No assurance can be given that the required stockholder, governmental and regulatory consents and approvals will be obtained or that the required conditions to closing will be satisfied, and, if all required consents and approvals are obtained and the required conditions are satisfied, no assurance can be given as to the terms, conditions and timing of such consents and approvals. Any delay in completing the Merger could cause the combined company not to realize, or to be delayed in realizing, some or all of the benefits that Assertio and Spectrum expect to achieve if the Merger is successfully completed within its expected time frame. For a more complete summary of the conditions that must be satisfied or waived prior to completion of the Merger, see “The Merger Agreement — Conditions to the Completion of the Merger.”

Assertio and Spectrum must obtain certain regulatory approvals and clearances to consummate the Merger, which, if delayed, not granted or granted with burdensome or unacceptable conditions, could prevent, substantially delay or impair consummation of the Merger, result in additional expenditures of money and resources or reduce the anticipated benefits of the Merger.

The completion of the Merger is subject to the termination or expiration of any applicable waiting period (or extension thereof) under the HSR Act relating to the transactions contemplated by the Merger Agreement. Regulators can also impose conditions on case approval under the applicable competition laws as they deem necessary or desirable, including, but not limited to, seeking divestiture of substantial assets of the parties or requiring the parties to license, or hold separate, assets or to not engage in certain types of conduct.

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Under the HSR Act, the Merger may not be completed until Notification and Report Forms have been filed with the U.S. Federal Trade Commission, which is referred to as the “FTC,” and the U.S. Department of Justice, which is referred to as the “DOJ,” and the applicable waiting period (or any extension thereof) has expired or been terminated. A transaction requiring notification under the HSR Act may not be completed until the expiration of the applicable 30-day waiting period following the parties’ filing of their respective HSR notifications or the early termination of that waiting period, at the earliest. Each of Assertio and Spectrum filed an HSR notification with the FTC and the DOJ on May 8, 2023 and the waiting period will expire at 11:59 p.m. Eastern Time on June 7, 2023.

At any time before or after consummation of the Merger, notwithstanding the expiration or termination of the applicable waiting period under the HSR Act, the DOJ or the FTC, or any state, could take such action under competition laws as it deems necessary or desirable in the public interest, including seeking to enjoin the completion of the Merger, seeking divestiture of substantial assets of the parties or requiring the parties to license, or hold separate, assets or to terminate existing relationships and contractual rights. Under certain circumstances, private parties may also seek to take legal action against the Merger under competition laws.

Failure to attract, motivate and retain executives and other key employees could diminish the anticipated benefits of the Merger.

The success of the Merger will depend in part on the combined company’s ability to retain the talents and dedication of the professionals currently employed by Assertio and Spectrum. It is possible that these employees may decide not to remain with Assertio or Spectrum, as applicable, while the Merger is pending, or with the combined company. If key employees terminate their employment, or if an insufficient number of employees are retained to maintain effective operations, the combined company’s business activities may be adversely affected and management’s attention may be diverted from successfully integrating Assertio and Spectrum to hiring suitable replacements, all of which may cause the combined company’s business to suffer. In addition, Assertio and Spectrum may not be able to locate suitable replacements for any key employees that leave either company or offer employment to potential replacements on reasonable terms. In addition, there could be disruptions to or distractions for the workforce and management, including disruptions associated with integrating employees into the combined company. No assurance can be given that the combined company will be able to attract or retain key employees of Assertio and Spectrum to the same extent that those companies have been able to attract or retain their own employees in the past.

The Merger, and uncertainty regarding the Merger, may cause customers, suppliers, distributors or strategic partners to delay or defer decisions concerning Assertio or Spectrum and adversely affect each company’s ability to effectively manage its respective business.

The Merger will happen only if the stated conditions are met, including the approval of the Assertio share issuance proposal, the approval of the Spectrum merger proposal and the receipt of required regulatory approvals, among other conditions. Many of the conditions are beyond the control of Assertio and Spectrum, and both parties also have certain rights to terminate the Merger Agreement. Accordingly, there may be uncertainty regarding the completion of the Merger. This uncertainty may cause customers, suppliers, distributors, vendors, strategic partners or others that deal with Assertio or Spectrum to delay or defer entering into contracts with Assertio or Spectrum or making other decisions concerning Assertio or Spectrum or seek to change or cancel existing business relationships with Assertio or Spectrum, which could negatively affect their respective businesses. Any delay or deferral of those decisions or changes in existing agreements could have an adverse impact on the respective businesses of Assertio and Spectrum, regardless of whether the Merger is ultimately completed.

In addition, the Merger Agreement restricts Assertio, Spectrum and each company’s respective subsidiaries from taking certain actions during the pendency of the Merger without the consent of the other party. These restrictions may prevent Assertio and Spectrum from pursuing attractive business opportunities or strategic transactions that may arise prior to the completion of the Merger. See “The Merger Agreement — Conduct of Business Prior to the Merger’s Completion” for a description of the restrictive covenants to which each of Assertio and Spectrum is subject.

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The opinions rendered to Assertio and Spectrum from their respective financial advisors will not reflect changes in circumstances between the dates of such opinions and the completion of the Merger.

SVB Securities and Wainwright delivered their oral opinions to the Assertio board of directors on April 24, 2023, which opinions were subsequently confirmed in a written opinion from each of SVB Securities and Wainwright dated as of April 24, 2023, to the effect that as of such date and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered in connection with the preparation of each opinion, the Merger Consideration was fair, from a financial point of view, to Assertio.

Guggenheim Securities delivered its oral opinion to the Spectrum board of directors on April 24, 2023, which opinion was subsequently confirmed in a written opinion dated as of April 24, 2023, that as of such date and based upon and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the scope of review undertaken as set forth in the written opinion, the exchange ratio and CVRs pursuant to the Merger Agreement was fair, from a financial point of view, to the holders of Spectrum common stock.

Neither Assertio nor Spectrum has obtained, nor will either of them obtain, an updated opinion from SVB Securities, Wainwright or Guggenheim Securities, as applicable, regarding the fairness, from a financial point of view, of the Merger Consideration, exchange ratio or CVRs, including as of the date of this joint proxy statement/prospectus or of the special meetings, or prior to the completion of the Merger. Each of the respective opinions of SVB Securities, Wainwright and Guggenheim Securities was necessarily based on general financial, economic, monetary, market and other conditions and circumstances as in effect on, and the information made available to SVB Securities, Wainwright and Guggenheim Securities, as applicable, only as of the dates of the respective opinions of SVB Securities, Wainwright and Guggenheim Securities, and such opinions do not address the fairness of the Merger Consideration, exchange ratio or CVRs, from a financial point of view, at the time the Merger is completed. Changes in the operations and prospects of Assertio or Spectrum, general financial, economic, monetary, market and other conditions, circumstances and factors that may be beyond the control of Assertio and Spectrum, and on which each of the respective opinions of SVB Securities, Wainwright and Guggenheim Securities was based, may alter the value of Assertio or Spectrum or the prices of shares of Assertio or Spectrum common stock by the time the Merger is completed. The opinions of SVB Securities, Wainwright and Guggenheim Securities do not speak as of any date other than the respective dates of such opinions. The recommendation of the Assertio board of directors that Assertio stockholders vote “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal and the recommendation of the Spectrum board of directors that Spectrum stockholders vote “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal are each made as of the date of this joint proxy statement/prospectus. For a description of the opinions that Assertio and Spectrum received from their respective financial advisors, see “The Merger — Opinions of Assertio’s Financial Advisors” and “The Merger — Opinion of Spectrum’s Financial Advisor.”

Whether or not the Merger is completed, the announcement and pendency of the Merger could cause disruptions in the businesses of Assertio and Spectrum, which could have an adverse effect on each company’s respective businesses and financial results.

Whether or not the Merger is completed, the announcement and pendency of the Merger could cause disruptions in the businesses of Assertio and Spectrum, including by diverting the attention of Assertio and Spectrum management toward the completion of the Merger. In addition, Assertio and Spectrum have each diverted significant management resources in an effort to complete the Merger and are each subject to restrictions contained in the Merger Agreement on the conduct of their respective businesses. If the Merger is not completed, Assertio and Spectrum will have incurred significant costs, including the diversion of management resources, for which they will have received little or no benefit.

Spectrum directors and executive officers have interests and arrangements that may be different from, or in addition to, those of Spectrum stockholders generally.

When considering the recommendations of the Spectrum board of directors on how to vote on the proposals described in this joint proxy statement/prospectus, Spectrum stockholders should be aware that

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Spectrum directors and executive officers have interests in the Merger that are different from, or in addition to, those of Spectrum stockholders generally. These interests include the continued service of certain Spectrum directors as directors of the combined company, the treatment in the Merger of outstanding equity, equity-based and incentive awards, severance arrangements, other compensation and benefit arrangements, and the right to continued indemnification of former Spectrum directors and officers by the combined company.

Spectrum stockholders should be aware of these interests when they consider the recommendations of the Spectrum board of directors that they vote to approve the Spectrum merger proposal. The Spectrum board of directors was aware of and considered these interests when it determined that the Merger was fair to and in the best interests of Spectrum and its stockholders, approved and declared advisable the Merger Agreement, and recommended that Spectrum stockholders adopt the Merger Agreement. The interests of Spectrum directors and executive officers are described in more detail under “Interests of Spectrum’s Directors and Executive Officers in the Merger.”

Assertio or Spectrum may waive one or more of the closing conditions without re-soliciting stockholder approval.

To the extent permitted by law, Assertio or Spectrum may determine to waive, in whole or part, one or more of the conditions to their respective obligations to consummate the Merger. Assertio and Spectrum currently expect to evaluate the materiality of any waiver and its effect on Assertio or Spectrum stockholders, as applicable, in light of the facts and circumstances at the time to determine whether any amendment of this joint proxy statement/prospectus or any re-solicitation of proxies is required in light of such waiver. Any determination as to whether to waive any condition to the Merger, and as to whether to re-solicit stockholder approval and/or amend this joint proxy statement/prospectus as a result of such waiver, will be made by Assertio or Spectrum, as applicable, at the time of such waiver based on the facts and circumstances as they exist at that time.

The Merger Agreement contains provisions that could discourage a potential competing acquirer that might be willing to pay more to acquire or merge with either Assertio or Spectrum.

The Merger Agreement contains “no solicitation” provisions that restrict the ability of Assertio and Spectrum to, among other things (each as described under “The Merger Agreement — No Solicitation of Acquisition Proposals”):

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initiate, solicit, knowingly assist, knowingly induce or knowingly encourage or facilitate (including by providing information) any inquiries, proposals or offers with respect to, or the making, submission, announcement or completion of, any proposal or offer that constitutes, or would be reasonably expected to lead to, an acquisition proposal;

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engage in, continue or participate in any discussions or negotiations with any person (other than Assertio or Spectrum and each of their respective affiliates and representatives, as applicable) concerning any acquisition proposal or any inquiry, proposal or offer that would reasonably be expected to lead to any acquisition proposal;

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furnish or provide or cause to be furnished or provided any non-public information or data relating to Assertio or Spectrum or their respective subsidiaries, as applicable, in connection with, or for the purpose of soliciting, initiating, encouraging or facilitating, or in response to, any inquiry, proposal or offer that constitutes or would reasonably be expected to lead to an acquisition proposal; or

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resolve or agree to do any of the foregoing.

Furthermore, there are only limited exceptions to the requirement under the Merger Agreement that neither the Assertio nor Spectrum boards of directors withdraw, change, qualify, withhold, amend or modify in any way adverse to the other party the Assertio recommendation or the Spectrum recommendation, as applicable (each as defined under “The Merger Agreement — Representations and Warranties”). Although the Assertio or Spectrum board of directors is permitted to effect a change of recommendation, after complying with certain procedures set forth in the Merger Agreement, in response to a superior proposal or to an intervening event (if the applicable board of directors determines in good faith, after consultation

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with its outside legal counsel and its financial advisor, that a failure to do so would be reasonably likely to be inconsistent with its fiduciary duties under applicable law), such change of recommendation would entitle the other party to terminate the Merger Agreement and collect a termination fee from the party making a change of recommendation. See “The Merger Agreement — Termination of the Merger Agreement” and “The Merger Agreement — Termination Fees.”

These provisions could discourage a potential competing acquirer from considering or proposing an acquisition or merger, even if it were prepared to pay consideration with a higher value than that implied by the exchange ratio in the Merger, or might result in a potential competing acquirer proposing to pay a lower per share price than it might otherwise have proposed to pay because of the added expense of the termination fee.

The Merger will involve substantial costs.

Assertio and Spectrum have incurred and expect to incur non-recurring costs associated with combining the operations of the two companies, as well as transaction fees and other costs related to the Merger. As of the date of this joint proxy statement/prospectus, Assertio and Spectrum estimate that their aggregate costs associated with the Merger and related transactions will be approximately $6.7 million and $10.7 million, respectively. These costs include filing and registration fees with the SEC, printing and mailing costs associated with this joint proxy/registration statement, and legal, accounting, investment banking, consulting, public relations and proxy solicitation fees. These costs do not include severance and retention payments that may be made to certain Spectrum employees and costs that will be incurred in connection with the integration of Assertio’s and Spectrum’s businesses. Some of these costs are payable by Assertio or Spectrum regardless of whether the Merger is completed.

The combined company will also incur restructuring and integration costs in connection with the Merger. The costs related to restructuring will be expensed as a cost of the ongoing results of operations of either Assertio or the combined company. There are processes, policies, procedures, operations, technologies and systems that must be integrated in connection with the Merger and the integration of Spectrum’s business. Although Assertio expects that the elimination of duplicative costs, strategic benefits, and additional income, as well as the realization of other efficiencies related to the integration of the businesses, may offset incremental transaction, Merger-related and restructuring costs over time, any net benefit may not be achieved in the near term or at all. Many of these costs will be borne by Assertio even if the Merger is not completed. While Assertio has assumed that certain expenses would be incurred in connection with the Merger and the other transactions contemplated by the Merger Agreement, there are many factors beyond Assertio’s control that could affect the total amount or the timing of the integration and implementation expenses.

Risks Relating to the CVRs

You may not receive any payment on the CVRs.

Your right to receive any future payment on the CVRs will be contingent upon achievement of a Milestone. If any of the Milestones are not achieved for any reason within the time periods specified in the CVR Agreement, no payment will be made under the CVRs, and the CVRs will expire valueless. Accordingly, the value, if any, of the CVRs is speculative, and the CVRs may ultimately have no value. See “The Contingent Value Rights Agreement.”

The CVRs are non-transferable and, therefore, the value of the CVRs is only realizable to the extent that Milestones are achieved.

Holders of the CVRs are not permitted to sell, assign, transfer, pledge, encumber, or in any other manner dispose of the CVRs, in whole or in part, other than in certain highly limited circumstances specified in the CVR Agreement. As a result of this non-transferability, you will realize value from the CVRs only if a Milestone is achieved. See “The Contingent Value Rights Agreement.”

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The Milestone Payments are capped based on Assertio’s stock price.

Even if a Milestone is satisfied, the amount of each Milestone Payment may be adjusted to an amount less than $0.10 (including zero) if the closing price of Assertio common stock at the closing of the Merger or on the date a notice of a Milestone Payment is sent to holders of the CVRs could result in the value of the Upfront Merger Consideration constituting less than 80% of the aggregate Merger Consideration. See “The Contingent Value Rights Agreement.”

Assertio shall cause its affiliates to use “diligent efforts” to achieve the Milestones, but, under certain circumstances, Assertio and its affiliates may not be required to take certain actions to achieve the Milestones, which would have an adverse effect on the value, if any, of the CVRs.

Commencing upon closing, Assertio shall cause its affiliates to use “diligent efforts” to achieve the Milestones. However, the CVR Agreement definition of “diligent efforts” allows for the consideration of a variety of factors in determining the efforts Assertio and its affiliates are required to use to achieve each Milestone, and it does not require Assertio and its affiliates to take all possible actions to achieve them. Under the CVR Agreement, the definition of “diligent efforts” requires Assertio’s affiliates to carry out such tasks in a good faith, diligent and sustained manner without undue interruption, pause or delay, which level is at least commensurate with the level of commercially reasonable efforts that a pharmaceutical company of comparable size and resources as those of Assertio and its affiliates would devote to a product of similar commercial potential and stage in development or product life as ROLVEDON, taking into account its safety, tolerability, and efficacy, its proprietary position (including patent coverage) and profitability (including pricing, supply costs and reimbursement status), the competitiveness of alternative third-party products, the regulatory structure involved, the regulatory environment, and technical, commercial, legal, scientific and/or medical factors. The CVR holders acknowledge that Assertio has a fiduciary obligation to operate its business in the best interests of its stockholders, and any potential obligation to pay the Milestone Payments under the CVR Agreement does not create any express or implied obligation to operate Assertio’s business in any particular manner in order to maximize such Milestone Payments. See “The Contingent Value Rights Agreement.”

The U.S. federal income tax treatment of the CVRs is subject to substantial uncertainty.

The treatment of the CVRs and payments, if any, made under the CVRs for U.S. federal income tax purposes is subject to substantial uncertainty. There is no legal authority directly addressing the U.S. federal income tax treatment of the receipt of the CVRs pursuant to the Merger and payments, if any, made under the CVRs. Accordingly, the amount of gain a holder of Spectrum common stock that is subject to U.S. federal income taxation recognizes, and the timing and character of such gain, with respect to the CVRs is uncertain.

Whether contingent payment rights with characteristics similar to the rights under a CVR should be treated as part of an “open transaction” or “closed transaction” is inherently factual in nature. Pursuant to U.S. Treasury regulations addressing contingent payment obligations analogous to the CVRs, if the fair market value of the CVRs is “reasonably ascertainable,” a holder of Spectrum common stock that is subject to U.S. federal income taxation should treat the transaction as a “closed transaction” and include the fair market value of the CVRs as additional consideration received in the Merger for purposes of determining gain or loss. On the other hand, if the fair market value of the CVRs cannot be “reasonably ascertained,” such holder should treat the transaction as an “open transaction” for purposes of determining gain or loss. These U.S. Treasury regulations state that only in “rare and extraordinary” cases would the value of contingent payment obligations not be reasonably ascertainable.

Although not free from doubt, for U.S. federal income tax purposes, Assertio intends to treat the CVRs as additional consideration paid in respect of shares of Spectrum common stock exchanged in the Merger as part of a “closed transaction” and, assuming the Merger qualifies for the Intended Tax Treatment (as defined under “U.S. Federal Income Tax Considerations Relating to the Merger”), as taxable “boot.” Assertio’s views and actions as of the date of the Merger are not dispositive with respect to the tax treatment or fair market value of the CVRs and are not binding on the IRS as to the tax treatment of the receipt of CVRs or the fair market value of the CVRs.

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See “U.S. Federal Income Tax Considerations Relating to the Merger” on page 169 of this joint proxy statement/prospectus for a more complete description of the treatment of the CVRs and payments, if any, made under the CVRs for U.S. federal income tax purposes.

The Milestones are subject to dollar-for-dollar reductions for costs associated with technology transfers.

Any costs associated with effecting a technology transfer with respect to ROLVEDON will be deducted on a dollar-for-dollar basis from the net revenue used to calculate if the Milestones were exceeded. See “The Contingent Value Rights Agreement.”

Risks Relating to the Combined Company

Combining the businesses of Assertio and Spectrum may be more difficult, costly or time-consuming than expected and the combined company may fail to realize the anticipated benefits of the Merger, which may adversely affect the combined company’s business results and negatively affect the value of the combined company’s common stock.

The success of the Merger will depend on, among other things, the ability of Assertio and Spectrum to combine their businesses in a manner that facilitates growth opportunities and realizes expected cost savings. Assertio and Spectrum have entered into the Merger Agreement because each believes that the Merger and the other transactions contemplated by the Merger Agreement are fair to and in the best interests of their respective stockholders and that combining the businesses of Assertio and Spectrum will produce benefits and cost savings. See “The Merger — Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger” and “The Merger — Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger.”

However, Assertio and Spectrum must successfully combine their respective businesses in a manner that permits these benefits to be realized. In addition, the combined company must achieve the anticipated growth and cost savings without adversely affecting current revenues and investments in future growth. If the combined company is not able to successfully achieve these objectives, the anticipated benefits of the Merger may not be realized fully, or at all, or may take longer to realize than expected.

An inability to realize the full extent of the anticipated benefits of the Merger and the other transactions contemplated by the Merger Agreement, as well as any delays encountered in the integration process, could have an adverse effect upon the revenues, level of expenses and operating results of the combined company, which may adversely affect the value of the common stock of the combined company.

In addition, the actual integration may result in additional and unforeseen expenses, and the anticipated benefits of the integration plan may not be realized. Actual growth and cost savings, if achieved, may be lower than what Assertio and Spectrum expect and may take longer to achieve than anticipated. If Assertio and Spectrum are not able to adequately address integration challenges, they may be unable to successfully integrate their operations or realize the anticipated benefits of the integration of the two companies.

The failure to successfully integrate the businesses and operations of Assertio and Spectrum in the expected time frame may adversely affect the combined company’s future results.

Assertio and Spectrum have operated and, until the completion of the Merger, will continue to operate independently. There can be no assurances that their businesses can be integrated successfully. It is possible that the integration process could result in the loss of key Assertio or Spectrum employees, the loss of customers, the disruption of either company’s or both companies’ ongoing businesses, inconsistencies in standards, controls, procedures and policies, unexpected integration issues, higher than expected integration costs, including any Milestone Payments under the CVRs, and an overall post-completion integration process that takes longer than originally anticipated. Specifically, the following issues, among others, must be addressed in integrating the operations of Assertio and Spectrum in order to realize the anticipated benefits of the Merger so the combined company performs as expected:

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combining the companies’ operations and corporate functions;

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combining the businesses of Assertio and Spectrum and meeting the capital requirements of the combined company, in a manner that permits the combined company to achieve any cost savings or other synergies anticipated to result from the Merger, the failure of which would result in the anticipated benefits of the Merger not being realized in the time frame currently anticipated or at all;

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integrating personnel from the two companies;

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integrating the companies’ technologies and technologies licensed from third parties;

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integrating and unifying the offerings and services available to customers;

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identifying and eliminating redundant and underperforming functions and assets;

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harmonizing the companies’ operating practices, employee development and compensation programs, internal controls and other policies, procedures and processes;

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maintaining existing agreements with customers, suppliers, distributors and vendors, avoiding delays in entering into new agreements with prospective customers, suppliers, distributors and vendors, and leveraging relationships with such third parties for the benefit of the combined company;

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addressing possible differences in business backgrounds, corporate cultures and management philosophies;

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consolidating the companies’ administrative and information technology infrastructure;

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coordinating distribution and marketing efforts;

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managing the movement of certain positions to different locations;

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coordinating geographically dispersed organizations; and

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effecting actions that may be required in connection with obtaining regulatory or other governmental approvals.

In addition, at times the attention of certain members of either company’s or both companies’ management and resources may be focused on completion of the Merger and the integration of the businesses of the two companies and diverted from day-to-day business operations or other opportunities that may have been beneficial to such company, which may disrupt each company’s ongoing business and the business of the combined company.

The combined company may not be able to retain customers, suppliers or distributors, or customers, suppliers or distributors may seek to modify contractual relationships with the combined company, which could have an adverse effect on the combined company’s business and operations. Third parties may terminate or alter existing contracts or relationships with Assertio or Spectrum.

As a result of the Merger, the combined company may experience impacts on relationships with customers, suppliers and distributors that may harm the combined company’s business and results of operations. Certain customers, suppliers or distributors may seek to terminate or modify contractual obligations following the Merger whether or not contractual rights are triggered as a result of the Merger. There can be no guarantee that customers, suppliers and distributors will remain with or continue to have a relationship with the combined company or do so on the same or similar contractual terms following the Merger. If any customers, suppliers or distributors seek to terminate or modify contractual obligations or discontinue the relationship with the combined company, then the combined company’s business and results of operations may be harmed. Furthermore, the combined company will not have long-term arrangements with many of its significant suppliers. If the combined company’s suppliers were to seek to terminate or modify an arrangement with the combined company, then the combined company may be unable to procure necessary supplies from other suppliers in a timely and efficient manner and on acceptable terms, or at all.

Assertio and Spectrum also have contracts with vendors, landlords, licensors and other business partners which may require Assertio or Spectrum, as applicable, to obtain consent from these other parties in connection with the Merger, or which may otherwise contain limitations applicable to such contracts following the Merger. If these consents cannot be obtained, the combined company may suffer a loss of

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potential future revenue, incur costs and lose rights that may be material to the combined company’s business. In addition, third parties with whom Assertio or Spectrum currently have relationships may terminate or otherwise reduce the scope of their relationship with either party in anticipation of the Merger. Any such disruptions could limit the combined company’s ability to achieve the anticipated benefits of the Merger. The adverse effect of any such disruptions could also be exacerbated by a delay in the completion of the Merger or by a termination of the Merger Agreement.

The combined company may be exposed to increased litigation, which could have an adverse effect on the combined company’s business and operations.

The combined company may be exposed to increased litigation from stockholders, customers, suppliers, distributors, consumers and other third parties due to the combination of Assertio’s and Spectrum’s businesses following the Merger. Such litigation may have an adverse impact on the combined company’s business and results of operations or may cause disruptions to the combined company’s operations.

The Assertio and Spectrum unaudited prospective financial information is inherently subject to uncertainties, the unaudited pro forma condensed combined financial information included in this document is preliminary and the combined company’s actual financial position and results of operations after the Merger may differ materially from these estimates and the unaudited pro forma condensed combined financial information included in this joint proxy statement/prospectus. The unaudited pro forma condensed combined financial information does not reflect the effect of any divestitures that may be required in connection with the Merger.

The unaudited pro forma condensed combined financial information and unaudited pro forma per share data included in this joint proxy statement/prospectus are presented for illustrative purposes only, contain a variety of adjustments, assumptions and preliminary estimates and are not necessarily indicative of what the combined company’s actual financial position or results of operations would have been had the Merger been completed on the dates indicated. The combined company’s actual results and financial position after the Merger may differ materially and adversely from the unaudited pro forma condensed combined financial information included in this joint proxy statement/prospectus. The unaudited pro forma condensed combined financial information does not reflect the effect of any divestitures that may be required in connection with the Merger. See “Comparative Historical Unaudited Pro Forma Per Share Data” and “Unaudited Pro Forma Condensed Combined Financial Statements.”

While presented with numeric specificity, the Assertio and Spectrum unaudited pro forma condensed combined financial information provided in this joint proxy statement/prospectus is based on numerous variables and assumptions (including, but not limited to, those related to industry performance and competition, general business, the semiconductor and related industries, and economic, market and financial conditions and additional matters specific to Assertio’s or Spectrum’s business, as applicable) that are inherently subjective and uncertain and are beyond the control of the respective management teams of Assertio and Spectrum. As a result, actual results may differ materially from the unaudited pro forma condensed combined financial information. Important factors that may affect actual results and cause these unaudited projected financial forecasts to not be achieved include, but are not limited to, risks and uncertainties relating to Assertio’s or Spectrum’s business, as applicable (including each company’s ability to achieve strategic goals, objectives and targets over applicable periods), industry performance, general business and economic conditions. See “The Merger — Assertio Unaudited Financial Projections,” “The Merger — Spectrum Unaudited Financial Projections” and “The Merger — Certain Estimated Synergies.”

The COVID-19 pandemic, including other pandemics, epidemics or outbreaks of a contagious disease, may affect the combined company’s business and operations.

The extent to which the COVID-19 pandemic, including other pandemics, epidemics or outbreaks of a contagious disease, may impact the combined company is highly uncertain and is difficult to predict. The effects and extent will depend on various factors, including, but not limited to, the duration, scope and impact of the illness, and restrictions on business and social distancing guidelines that may be requested or mandated by governmental authorities, including limitations on elective surgeries and in-person physician visits. The impacts include, but are not limited to, delays in the initiation and enrollment of clinical trials, supply chain disruptions, prescriber behavior due to increases in virtual physician visits and volatility of

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prescriptions associated with elective procedures. For example, although many COVID-19 public health restrictions have eased, future surges could result in additional restrictions or other factors that may contribute to decreases in elective procedures, which in turn may impact the prescriptions associated with these procedures. Ultimately, efforts to mitigate the impact of COVID-19 or any other public health outbreak may not completely prevent the combined company’s business from being adversely affected and future impacts remain uncertain.

Any impairment of the combined company’s tangible, definite-lived intangible or indefinite-lived intangible assets, including goodwill, may adversely impact the combined company’s financial position and results of operations.

The Merger will be accounted for using the acquisition method of accounting under the provisions of ASC 805, Business Combinations, with Assertio representing the accounting acquirer under this guidance. Assertio will record assets acquired, including identifiable intangible assets, and liabilities assumed from Spectrum at their respective fair values at the date of completion of the Merger. Any excess of the purchase price over the net fair value of such assets and liabilities will be recorded as goodwill. In connection with the Merger, the combined company is expected to record significant goodwill and other intangible assets on its consolidated balance sheet. See “Unaudited Pro Forma Condensed Combined Financial Statements.”

Indefinite-lived intangible assets, including goodwill, will be tested for impairment at least annually, and all tangible and intangible assets including goodwill will be tested for impairment when certain indicators are present. If, in the future, the combined company determines that tangible or intangible assets, including goodwill, are impaired, the combined company would record an impairment charge at that time. Impairment testing of goodwill and intangible assets requires significant use of judgment and assumptions, particularly as it relates to the determination of fair value. A decrease in the long-term economic outlook and future cash flows of the combined company’s business could significantly impact asset values and potentially result in the impairment of intangible assets, including goodwill, which may have a material adverse impact on the combined company’s financial position and results of operations.

The Assertio bylaws designate the Court of Chancery of the State of Delaware and, to the extent enforceable, the U.S. federal district courts as the exclusive forums for substantially all disputes between Assertio and its stockholders, which will restrict the ability of stockholders of the combined company to choose the judicial forum for disputes with the combined company or its directors, officers or employees.

The Assertio bylaws provide that, unless Assertio consents in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware is, to the fullest extent permitted by law, the sole and exclusive forum for the following claims, including claims in the right of Assertio: (i) that are based upon a violation of a duty by a current or former director, officer, employee or stockholder in such capacity; or (ii) as to which the DGCL confers jurisdiction upon the Court of Chancery. Nothing in the Assertio charter or the Assertio bylaws would preclude stockholders that assert claims under the Exchange Act from bringing such claims in federal court to the extent the Exchange Act confers exclusive federal jurisdiction over such claims, subject to applicable law.

Section 22 of the Securities Act creates concurrent jurisdiction for federal and state courts over all Securities Act actions. Accordingly, both state and federal courts have jurisdiction to entertain such claims. The Assertio bylaws provide that the U.S. federal district courts are the exclusive forum for resolving any complaint asserting a cause of action arising under the Securities Act. However, there is uncertainty as to whether a court would enforce such a forum selection provision as written in connection with claims arising under the Securities Act.

These forum selection provisions may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with the combined company or its directors, officers or other employees, which may discourage such lawsuits. While Delaware courts have determined that such forum selection provisions are facially valid, a stockholder may nevertheless seek to bring such a claim arising under the Securities Act against the combined company and its directors, officers or other employees in a venue other than in the U.S. federal district courts. In such instance, the combined company would expect to vigorously assert the validity and enforceability of these forum selection provisions. This may require further significant additional costs associated with resolving the dispute in other jurisdictions, and there can be no assurance

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that the forum selection provisions will be enforced by a court in those other jurisdictions, any of which could seriously harm the combined company’s business.

Other Risk Factors of Assertio and Spectrum

Assertio’s and Spectrum’s businesses are and will be subject to the risks described above. In addition, Assertio and Spectrum are, and will continue to be, subject to the risks described in, as applicable, Assertio’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022 and Spectrum’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022, Assertio’s Quarterly Report on Form 10-Q for the three months ended March 31, 2023 and Spectrum’s Quarterly Report on Form 10-Q for the three months ended March 31, 2023 as such risks may be updated or supplemented in each company’s subsequently filed Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, each of which are filed with the SEC and incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.”

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THE PARTIES TO THE MERGER

Assertio Holdings, Inc.

100 South Saunders Rd., Suite 300
Lake Forest, IL 60045
(224) 419-7106

Assertio is a commercial pharmaceutical company offering differentiated products to patients utilizing a non-personal promotional model. Its commercial portfolio of branded products focuses on three areas: neurology, rheumatology, and pain and inflammation. It has built its commercial portfolio through a combination of increased opportunities with existing products, as well as through acquisition and licensing of additional approved products. With 29 employees, Assertio’s principal executive offices are located at 110 South Saunders Rd., Suite 300, Lake Forest, IL 60045, and its telephone number is (224) 419-7106.

Assertio is a Delaware corporation and the Assertio common stock is listed on Nasdaq SM under the ticker symbol “ASRT.”

For more information about Assertio, visit Assertio’s website at www.assertiotx.com. The information contained on or accessible through Assertio’s website (other than the documents incorporated by reference herein) does not constitute a part of this joint proxy statement/prospectus or any other report or document on file with or furnished to the SEC. Additional information about Assertio is included in the documents incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.”

Spectrum Pharmaceuticals, Inc.

Pilot House — Lewis Wharf
2 Atlantic Avenue, 6th Floor,
Boston, Massachusetts 02110
(617) 586-3900

Spectrum is a Delaware corporation and the Spectrum common stock is listed on Nasdaq CM under the ticker symbol “SPPI.”

For more information about Spectrum, visit Spectrum’s website at www.sppirx.com. The information contained on or accessible through Spectrum’s website (other than the documents incorporated by reference herein) does not constitute a part of this joint proxy statement/prospectus or any other report or document on file with or furnished to the SEC. Additional information about Spectrum is included in the documents incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.”

Spade Merger Sub 1, Inc.

100 South Saunders Rd., Suite 300
Lake Forest, IL 60045
(224) 419-7106

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THE ASSERTIO SPECIAL MEETING

This joint proxy statement/prospectus is being provided to Assertio stockholders in connection with the solicitation of proxies by the Assertio board of directors for use at the Assertio special meeting and at any adjournments or postponements thereof. Assertio stockholders are encouraged to read this entire document carefully, including its annexes and the documents incorporated by reference herein, for more detailed information regarding the Merger Agreement and the transactions contemplated thereby.

Date, Time and Place of the Assertio Special Meeting

The Assertio special meeting is scheduled to be held virtually via live webcast on July 27, 2023, beginning at 12:30 p.m., Central Time, unless postponed to a later date.

Assertio has elected to hold the Assertio special meeting solely by means of remote communication via live webcast. Assertio stockholders will be able to virtually attend and vote at the Assertio special meeting by visiting https://www.cstproxy.com/assertiotx/sm2023 (the “Assertio special meeting website”). Assertio stockholders will need the 12-digit control number found on their proxy card in order to access the Assertio special meeting website and to access the list of Assertio stockholders entitled to vote at the Assertio special meeting during the time of the meeting.

Assertio has retained Continental Stock Transfer to host the live webcast of the Assertio special meeting. On the day of the Assertio special meeting, Continental Stock Transfer may be contacted at (917) 262-2373, and will be available to answer any questions regarding how to virtually attend the Assertio special meeting or if you encounter any technical difficulty accessing or during the Assertio special meeting.

Matters to Be Considered at the Assertio Special Meeting

The purpose of the Assertio special meeting is to consider and vote on each of the following proposals, each of which is further described in this joint proxy statement/prospectus:

•

Assertio Proposal 1: Approval of the Share Issuance. To consider and vote on the Assertio share issuance proposal; and

•

Assertio Proposal 2: Adjournment of the Assertio Special Meeting. To consider and vote on the Assertio adjournment proposal.

Recommendation of the Assertio Board of Directors

The Assertio board of directors unanimously recommends that Assertio stockholders vote:

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Assertio Proposal 1: “FOR” the Assertio share issuance proposal; and

•

Assertio Proposal 2: “FOR” the Assertio adjournment proposal.

After careful consideration, the Assertio board of directors unanimously: (i) determined that the terms of the Merger Agreement and the Merger are fair to and in the best interests of Assertio and its stockholders; (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Merger and the share issuance, each on the terms and subject to the conditions set forth in the Merger Agreement; and (iii) recommended that Assertio stockholders approve of the Assertio share issuance proposal. See “The Merger — Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger.”

Record Date for the Assertio Special Meeting and Voting Rights

The record date to determine Assertio stockholders who are entitled to receive notice of and to vote at the Assertio special meeting or any adjournments or postponements thereof is June 13, 2023. As of the close of business on the Assertio record date, there were 56,512,962 shares of Assertio common stock issued and outstanding and entitled to vote at the Assertio special meeting.

Each Assertio stockholder is entitled to one vote for each share of Assertio common stock such holder owned of record at the close of business on the Assertio record date with respect to each matter properly

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brought before the Assertio special meeting. Only Assertio stockholders of record at the close of business on the Assertio record date are entitled to receive notice of and to vote at the Assertio special meeting and any and all adjournments or postponements thereof.

Quorum; Abstentions and Broker Non-Votes

A quorum of Assertio stockholders is necessary to conduct the Assertio special meeting. On June 12, 2023, the Assertio board of directors adopted an amendment to the Assertio bylaws lowering the quorum threshold from holders of a majority of the voting power of the issued and outstanding shares of Assertio common stock entitled to vote at a meeting to 331∕3%. This change to the bylaws was made as a result of historical difficulties Assertio has faced in seeking to obtain a quorum at its stockholder meetings (difficulties that are heightened in situations like the Assertio special meeting where there are no “routine” matters on the agenda), the high percentage of retail stockholders in Assertio’s stockholder base and the fact that Assertio is not, as of the Assertio record date, a member of any major trading index. Given these factors, the Assertio board of directors determined that, in order to address this ongoing issue (including with respect to the Assertio special meeting), a decrease in Assertio’s quorum threshold was appropriate. The Assertio board of directors also took into account that the new quorum requirement of 331∕3% generally is consistent with practices at other similarly situated specialty pharmaceutical companies. The Assertio board of directors further determined to reassess the necessity of this lower quorum threshold in the future should Assertio’s circumstances change.

Because of the bylaws amendment discussed above, the presence, virtually via the Assertio special meeting website or by proxy, of the holders of 331∕3% of the voting power of the issued and outstanding shares of Assertio common stock entitled to vote at the Assertio special meeting will constitute a quorum. Shares of Assertio common stock represented at the Assertio special meeting by virtual attendance via the Assertio special meeting website or by proxy and entitled to vote, but not voted, including shares for which an Assertio stockholder directs an “abstention” from voting, will be counted for purposes of determining a quorum. However, because all of the proposals for consideration at the Assertio special meeting are considered “non-routine” matters under Nasdaq SM rules (as described below), shares held in “street name” will not be counted as present for the purpose of determining the existence of a quorum unless the Assertio stockholder provides their bank, broker or other nominee with voting instructions for at least one of the proposals at the Assertio special meeting. If a quorum is not present, the Assertio special meeting will be adjourned or postponed until the holders of the number of shares of Assertio common stock required to constitute a quorum attend.

Under Nasdaq SM rules, banks, brokers or other nominees who hold shares in “street name” on behalf of the beneficial owner of such shares have the authority to vote such shares in their discretion on certain “routine” proposals when they have not received voting instructions from the beneficial owners. However, banks, brokers or other nominees are not allowed to exercise their voting discretion with respect to matters that under Nasdaq SM rules are “non-routine.” This can result in a “broker non-vote,” which occurs on an item when (i) a bank, broker or other nominee has discretionary authority to vote on one or more “routine” proposals to be voted on at a meeting of stockholders, but is not permitted to vote on other “non-routine” proposals without instructions from the beneficial owner of the shares, and (ii) the beneficial owner fails to provide the bank, broker or other nominee with voting instructions on a “non-routine” matter. All of the proposals before the Assertio special meeting are considered “non-routine” matters under Nasdaq SM rules, and banks, brokers or other nominees will not have discretionary authority to vote on any matter before the Assertio special meeting. As a result, Assertio does not expect any broker non-votes at the Assertio special meeting and if you hold your shares of Assertio common stock in “street name,” your shares will not be represented and will not be voted on any matter unless you affirmatively instruct your bank, broker or other nominee how to vote your shares in accordance with the voting instructions provided by your bank, broker or other nominee. It is therefore critical that you cast your vote by instructing your bank, broker or other nominee on how to vote. Brokers will not be able to vote on any of the proposals before the Assertio special meeting unless they have received voting instructions from the beneficial owners.

Required Votes

Except for the Assertio adjournment proposal, the vote required to approve each of the proposals listed below assumes the presence of a quorum at the Assertio special meeting. As described above, Assertio does not expect there to be any broker non-votes at the Assertio special meeting.

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Proposal	Required Vote	Effects of Certain Actions
Assertio Proposal 1: Assertio share issuance proposal	Approval requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal.	Any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio share issuance proposal.
		An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio share issuance proposal to vote on the Assertio share issuance proposal will have the same effect as a vote “AGAINST” the Assertio share issuance proposal. However, assuming a quorum is present at the Assertio special meeting, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but not for the Assertio share issuance proposal, voting power will deemed to be withheld with respect to the Assertio share issuance proposal and such failure to provide voting instructions will have no effect on the Assertio share issuance proposal.
Assertio Proposal 2: Assertio adjournment proposal	Approval requires the affirmative vote of the holders of a majority of the issued and outstanding shares of Assertio common stock that are virtually present via the Assertio special meeting website or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal.	Any shares not virtually present or represented by proxy (including due to the failure of an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee to provide voting instructions to such bank, broker or other nominee) will have no effect on the outcome of the Assertio adjournment proposal.
		An abstention or other failure of any shares virtually present or represented by proxy and entitled to vote at the Assertio special meeting on the Assertio adjournment proposal will have the same effect as a vote “AGAINST” the Assertio adjournment proposal. However, if an Assertio stockholder who holds shares in “street name” through a bank, broker or other nominee provides voting instructions for one or more other proposals, but

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Proposal			Required Vote			Effects of Certain Actions
						not for the Assertio adjournment proposal, voting power will deemed to be withheld with respect to the Assertio adjournment proposal and such failure to provide voting instructions will have no effect on the Assertio adjournment proposal.

Vote of Assertio Directors and Executive Officers

As of June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, Assertio directors and executive officers, and their affiliates, as a group, owned and were entitled to vote approximately 2.8% of the total outstanding shares of Assertio common stock. Although none of them has entered into any agreement obligating them to do so, Assertio currently expects that all Assertio directors and executive officers will vote their shares “FOR” the Assertio share issuance proposal and “FOR” the Assertio adjournment proposal. See “Interests of Assertio’s Directors and Executive Officers in the Merger.”

Methods of Voting

Registered Stockholders

If you are an Assertio stockholder of record, you may vote at the Assertio special meeting by proxy over the internet or telephone or by mail, or by virtually attending and voting at the Assertio special meeting via the Assertio special meeting website, as described below.

•

By Internet: By following the instructions provided on your proxy card.

•

By Telephone: By following the instructions provided on your proxy card.

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By Mail: If you have received a paper copy of the proxy materials by mail, you may complete and return by mail the enclosed proxy card in the postage-paid envelope.

•

Virtually via the Assertio Special Meeting Website: By visiting the Assertio special meeting website, you can virtually attend and vote at the Assertio special meeting. Assertio stockholders who plan to virtually attend the Assertio special meeting will need the 12-digit control number included on their proxy card in order to access the Assertio special meeting website.

Unless revoked, all duly executed proxies representing shares of Assertio common stock entitled to vote at the Assertio special meeting will be voted at the Assertio special meeting and, where a choice has been specified on the proxy card, will be voted in accordance with such specification. If you submit an executed proxy without providing instructions for any proposal, then the Assertio officers identified on the proxy will vote your shares consistent with the recommendation of the Assertio board of directors on such proposal. If you are an Assertio stockholder of record, proxies submitted over the internet or by telephone as described above must be received by 11:59 p.m., Central Time, on July 26, 2023. To reduce administrative costs and help the environment by conserving natural resources, Assertio asks that you submit a proxy to vote your shares through the internet or by telephone.

By executing and delivering a proxy in connection with the Assertio special meeting, you designate certain Assertio officers identified therein as your proxies at the Assertio special meeting. If you deliver an executed proxy, but do not specify a choice for any proposal properly brought before the Assertio special meeting, such proxies will vote your shares of Assertio common stock on such uninstructed proposal in accordance with the recommendation of the Assertio board of directors. Assertio does not expect that any matter other than the proposals listed above will be brought before the Assertio special meeting, and the Assertio bylaws provide that the only business that may be conducted at the Assertio special meeting are those proposals brought before the Assertio special meeting by or at the direction of the Assertio board of directors.

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Beneficial (Street Name) Stockholders

If you hold your shares of Assertio common stock through a bank, broker or other nominee in “street name” instead of as a registered holder, you must follow the voting instructions provided by your bank, broker or other nominee in order to vote your shares. Your voting instructions must be received by your bank, broker or other nominee prior to the deadline set forth in the information from your bank, broker or other nominee on how to submit voting instructions. If you do not provide voting instructions to your bank, broker or other nominee for a proposal, your shares of Assertio common stock will not be voted on that proposal because your bank, broker or other nominee does not have discretionary authority to vote on any of the proposals to be voted on at the Assertio special meeting. See “The Assertio Special Meeting — Quorum; Abstentions and Broker Non-Votes.”

If you hold your shares of Assertio common stock through a bank, broker or other nominee in “street name” (instead of as a registered holder), you must obtain a specific control number from your bank, broker or other nominee in order to virtually attend and vote at the Assertio special meeting via the Assertio special meeting website. See “The Assertio Special Meeting — Virtually Attending the Assertio Special Meeting.”

Revocability of Proxies

Any Assertio stockholder giving a proxy has the right to revoke it at any time before the proxy is voted at the Assertio special meeting. If you are an Assertio stockholder of record, you may revoke your proxy by any one of the following actions:

•

by sending a signed written notice of revocation to Assertio, provided such notice is received no later than the close of business on July 26, 2023;

•

by voting again over the internet or telephone as instructed on your proxy card before the closing of the voting facilities at 11:59 p.m., Central Time, on July 26, 2023;

•

by submitting a properly signed and dated proxy card with a later date that is received by Assertio no later than the close of business on July 26, 2023; or

•

by virtually attending the Assertio special meeting via the Assertio special meeting website and requesting that your proxy be revoked, or virtually voting via the Assertio special meeting website as described above.

Only your last submitted proxy will be considered.

Execution or revocation of a proxy will not in any way affect an Assertio stockholder’s right to virtually attend and vote at the Assertio special meeting via the Assertio special meeting website.

Written notices of revocation and other communications relating to the revocation of proxies should be addressed to:

Assertio Holdings, Inc.
Attn: General Counsel
corpgov@assertiotx.com
100 South Saunders Road, Suite 300
Lake Forest, IL 60045

If your shares of Assertio common stock are held in “street name” and you previously provided voting instructions to your broker, bank or other nominee, you should follow the instructions provided by your broker, bank or other nominee to revoke or change your voting instructions. You may also change your vote by obtaining your specific control number and instructions from your bank, broker or other nominee and voting your shares at the Assertio special meeting via the Assertio special meeting website.

Proxy Solicitation Costs

Assertio is soliciting proxies to provide an opportunity to all Assertio stockholders to vote on agenda items, whether or not such Assertio stockholders are able to virtually attend the Assertio special meeting or

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any adjournment or postponement thereof. Assertio will bear the entire cost of soliciting proxies from Assertio stockholders. In addition to the solicitation of proxies by mail, Assertio will request that banks, brokers and other nominee record holders send proxies and proxy material to the beneficial owners of Assertio common stock and secure their voting instructions, if necessary. Assertio may be required to reimburse those banks, brokers and other nominees on request for their reasonable expenses in taking those actions.

Assertio has also retained Alliance Advisors, LLC to assist in soliciting proxies and in communicating with Assertio stockholders and estimates that it will pay them a fee of approximately $65,000, plus reimbursement for certain out-of-pocket fees and expenses. Assertio also has agreed to indemnify Alliance Advisors, LLC against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions). Proxies may be solicited on behalf of Assertio or by Assertio directors, officers and other employees in person or by mail, telephone, facsimile, messenger, the internet or other means of communication, including electronic communication. Assertio directors, officers and employees will not be paid any additional amounts for their services or solicitation in this regard.

Virtually Attending the Assertio Special Meeting

If you wish to virtually attend the Assertio special meeting via the Assertio special meeting website, you must (i) be a Assertio stockholder of record at the close of business on June 13, 2023 (the Assertio record date), (ii) hold your shares of Assertio common stock beneficially in the name of a broker, bank or other nominee as of the Assertio record date or (iii) hold a valid proxy for the Assertio special meeting.

To enter the Assertio special meeting website and virtually attend the Assertio special meeting, you will need the 12-digit control number located on your proxy card. If you hold your shares of Assertio common stock in street name beneficially through a broker, bank or other nominee and you wish to virtually attend the Assertio special meeting via the Assertio special meeting website, you will need to obtain your specific control number and further instructions from your bank, broker or other nominee. The 12-digit control number is also needed to access the list of Assertio stockholders entitled to vote at the Assertio special meeting during the time of the meeting.

If you plan to virtually attend and vote at the Assertio special meeting via the Assertio special meeting website, Assertio still encourages you to vote in advance by the internet, telephone or (if you received a paper copy of the proxy materials) by mail so that your vote will be counted even if you later decide not to virtually attend the Assertio special meeting via the Assertio special meeting website. Voting your proxy by the internet, telephone or mail will not limit your right to virtually attend and vote at the Assertio special meeting via the Assertio special meeting website if you later decide to do so.

Householding

SEC rules permit companies and intermediaries such as brokers to satisfy delivery requirements for proxy statements and notices with respect to two or more stockholders sharing the same address by delivering a single proxy statement or a single notice addressed to those stockholders. This process, which is commonly referred to as “householding,” provides cost savings for companies. Assertio has previously adopted householding for Assertio stockholders of record. As a result, Assertio stockholders with the same address and last name may receive only one copy of this joint proxy statement/prospectus. Registered Assertio stockholders (those who hold shares of Assertio common stock directly in their name with Assertio’s transfer agent) may opt out of householding and receive a separate joint proxy statement/prospectus or other proxy materials by sending a written request to Assertio at the address below.

Some brokers household proxy materials, delivering a single proxy statement or notice to multiple Assertio stockholders sharing an address unless contrary instructions have been received from the affected stockholders. Once you have received notice from your broker that they will be householding materials to your address, householding will continue until you are notified otherwise or until you revoke your consent. If, at any time, you no longer wish to participate in householding and would prefer to receive a separate proxy statement or notice, or if your household is receiving multiple copies of these documents and you wish to request that future deliveries be limited to a single copy, please notify your broker.

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Assertio will promptly deliver a copy of this joint proxy statement/prospectus to any Assertio stockholder who only received one copy of these materials due to householding upon request in writing to: Assertio Holdings, Inc., 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045 or by calling (224) 419-7106.

Tabulation of Votes

The Assertio board of directors will appoint an independent inspector of election for the Assertio special meeting. The inspector of election will, among other matters, determine the number of shares of Assertio common stock virtually present or represented by proxy at the Assertio special meeting to confirm the existence of a quorum, determine the validity of all proxies and ballots and certify the results of voting on all proposals submitted to Assertio stockholders at the Assertio special meeting.

Adjournments

If a quorum is present at the Assertio special meeting but there are insufficient votes at the time of the Assertio special meeting to approve the Assertio share issuance proposal, then Assertio stockholders may be asked to vote on the Assertio adjournment proposal.

At any subsequent reconvening of the Assertio special meeting at which a quorum is present, any business may be transacted that might have been transacted at the original meeting, and all proxies will be voted in the same manner as they would have been voted at the original convening of the Assertio special meeting, except for any proxies that have been effectively revoked or withdrawn prior to the time the proxy is voted at the reconvened meeting.

Assistance

If you need assistance voting or completing your proxy card, or if you have questions regarding the Assertio special meeting, please contact Alliance Advisors, LLC, Assertio’s proxy solicitor for the Assertio special meeting, at:

Alliance Advisors, LLC
200 Broadacres Drive, 3rd Floor
Bloomfield, NY 07003
(973) 873-7700
www.allianceadvisors.com

ASSERTIO STOCKHOLDERS SHOULD CAREFULLY READ THIS JOINT PROXY STATEMENT/PROSPECTUS IN ITS ENTIRETY FOR MORE DETAILED INFORMATION CONCERNING THE MERGER AGREEMENT AND THE MERGER. IN PARTICULAR, ASSERTIO STOCKHOLDERS ARE DIRECTED TO THE MERGER AGREEMENT, WHICH IS ATTACHED AS ANNEX A HERETO.

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ASSERTIO PROPOSAL 1: APPROVAL OF THE SHARE ISSUANCE

This joint proxy statement/prospectus is being furnished to you as an Assertio stockholder in connection with the solicitation of proxies by the Assertio board of directors for use at the Assertio special meeting. At the Assertio special meeting, Assertio is asking Assertio stockholders to consider and vote upon a proposal to approve the issuance of shares of Assertio common stock to Spectrum stockholders in connection with the Merger. Based on the number of shares of Spectrum common stock outstanding as of June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, Assertio expects to issue approximately 36.6 million shares of Assertio common stock to Spectrum stockholders in connection with the Merger. The actual number of shares of Assertio common stock to be issued in connection with the Merger will be determined at the effective time based on the exchange ratio of 0.1783 shares of Assertio common stock for each share of Spectrum common stock and the number of shares of Spectrum common stock outstanding at such time. Based on the number of shares of Assertio common stock and Spectrum common stock outstanding as of June 13, 2023, the latest practicable date prior to the date of this joint proxy statement/prospectus, upon completion of the Merger (without consideration of the shares of Assertio common stock underlying the CVRs), former Spectrum stockholders are expected to own approximately 35% of the outstanding shares of Assertio common stock and Assertio stockholders immediately prior to the Merger are expected to own approximately 65% of the outstanding shares of Assertio common stock.

The Assertio board of directors, after careful consideration, unanimously determined that the terms of the Merger Agreement and the Merger are fair to and in the best interests of Assertio and its stockholders, and approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Merger and the share issuance.

The Assertio board of directors unanimously recommends that Assertio stockholders vote “FOR” the Assertio share issuance proposal.

IF YOU ARE AN ASSERTIO STOCKHOLDER, THE ASSERTIO BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” THE ASSERTIO SHARE ISSUANCE PROPOSAL
(“ASSERTIO PROPOSAL 1”)

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ASSERTIO PROPOSAL 2: ADJOURNMENT OF THE ASSERTIO SPECIAL MEETING

The Assertio special meeting may be adjourned to another time and place if necessary or appropriate to permit the solicitation of additional proxies if there are insufficient votes to approve the Assertio share issuance proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Assertio stockholders.

Assertio is asking Assertio stockholders to authorize the holder of any proxy solicited by the Assertio board of directors to vote in favor of any adjournment of the Assertio special meeting, if necessary or appropriate, to solicit additional proxies if there are insufficient votes to approve the Assertio share issuance proposal or to ensure that any supplement or amendment to this joint proxy statement/prospectus is timely provided to Assertio stockholders.

The Assertio board of directors unanimously recommends that Assertio stockholders vote “FOR” the Assertio adjournment proposal.

IF YOU ARE AN ASSERTIO STOCKHOLDER, THE ASSERTIO BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT YOU VOTE “FOR” THE ASSERTIO ADJOURNMENT PROPOSAL
(“ASSERTIO PROPOSAL 2”)

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THE SPECTRUM SPECIAL MEETING

General

This joint proxy statement/prospectus is first being mailed on or about June 15, 2023, and constitutes notice of the Spectrum special meeting in conformity with the requirements of the DGCL and the Spectrum bylaws.

This joint proxy statement/prospectus is being provided to Spectrum stockholders as part of a solicitation of proxies by the Spectrum board of directors for use at the Spectrum special meeting and at any adjournment or postponement of the Spectrum special meeting. Before voting, Spectrum stockholders are encouraged to read the entire document carefully, including the annexes to this document, for more detailed information regarding the Merger Agreement and the transactions contemplated by the Merger Agreement.

Date, Time and Place

You are invited to attend the Spectrum special meeting on July 27, 2023 at 10:00 a.m. Eastern Time, which will be held virtually and can be accessed at www.meetnow.global/MYXFZTA where Spectrum stockholders will be able to participate and vote online. This joint proxy statement/prospectus is first being mailed to Spectrum’s stockholders on or about June 15, 2023.

We may announce alternative arrangements for the Spectrum special meeting, which may include switching to a hybrid in-person/virtual format, an in-person format or changing the time, date or location of the Spectrum special meeting. If we take this step, we will announce any changes through a press release that will also be filed with the SEC as additional proxy materials and we will post details at http://investor.sppirx.com/shareholder-services.

Purpose of the Spectrum Special Meeting

At the Spectrum special meeting, Spectrum stockholders will be asked to consider and vote on the following:

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the Spectrum merger proposal;

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the Spectrum advisory compensation proposal; and

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the Spectrum adjournment proposal.

Spectrum will transact no other business at the Spectrum special meeting except such business as may properly be brought before the Spectrum special meeting or any adjournment or postponement thereof by or at the direction of the Spectrum board of directors in accordance with the Spectrum bylaws. This joint proxy statement/prospectus, including the Merger Agreement attached hereto as Annex A, contains further information with respect to these matters.

Recommendation of the Spectrum Board of Directors

The Spectrum board of directors has (i) determined that the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement are fair and in the best interest of, and are advisable to, Spectrum and the Spectrum stockholders, (ii) approved and adopted the Merger Agreement and approved the Merger and the other transactions contemplated by the Merger Agreement and (iii) recommended that the Spectrum stockholders approve the Merger Agreement. A description of factors considered by the Spectrum board of directors in reaching its decision to approve and declare advisable the foregoing proposals can be found in the section titled “The Merger — Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger” beginning on page 86 of this joint proxy statement/prospectus.

The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal at the Spectrum special meeting.

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Approval of the Spectrum merger proposal is a condition for the Merger to occur. If Spectrum stockholders fail to approve the Spectrum merger proposal by the requisite vote, the Merger will not occur.

Record Date; Stockholders Entitled to Vote

Only Spectrum stockholders at the close of business on June 13, 2023, the record date for the Spectrum special meeting, will be entitled to notice of, and to vote at, the Spectrum special meeting or any adjournment or postponement of the Spectrum special meeting. At the close of business on the Spectrum record date, 205,245,727 shares of Spectrum common stock were issued and outstanding.

Each Spectrum stockholder is entitled to one vote for each share of Spectrum common stock that is outstanding in his, her or its name on Spectrum’s books as of close of business on the Spectrum record date.

A list of Spectrum stockholders of record entitled to vote at the Spectrum special meeting will be available for examination by any Spectrum stockholder for any legally valid purpose at Spectrum’s corporate headquarters, located at 2 Atlantic Avenue, 6th Floor, Boston, MA 02110, for a period of ten days prior to the Spectrum special meeting in accordance with the Spectrum bylaws and the DGCL. The list of eligible Spectrum stockholders of record also will be available for inspection during the Spectrum special meeting at www.meetnow.global/MYXFZTA by entering the 15-digit control number provided on your proxy card or voting instruction form and completing the required online attestation form.

Quorum; Adjournment

The holders of record of 331∕3% of the issued and outstanding shares of Spectrum common stock as of the Spectrum record date entitled to vote at the Spectrum special meeting, present in person or represented by proxy, will constitute a quorum for the transaction of business at the Spectrum special meeting. Virtual attendance by stockholders of record at the Spectrum special meeting will constitute presence in person for the purpose of determining the presence of a quorum for the transaction of business at the Spectrum special meeting. If you hold shares of Spectrum common stock in “street name,” your shares will not be counted towards a quorum unless you give voting instructions to your bank, broker, trustee or other nominee or obtain a legal proxy from your bank, broker, trustee or other nominee that enables you to attend the Spectrum special meeting. There must be a quorum for business to be conducted at the Spectrum special meeting.

Failure of a quorum to be represented at the Spectrum special meeting will result in an adjournment of the Spectrum special meeting and may subject Spectrum to additional expense. The chairperson of the meeting will have the right and authority to recess and/or adjourn the Spectrum special meeting and, if a quorum is not present at the Spectrum special meeting, Spectrum stockholders holding a majority in voting power of shares of Spectrum capital stock, present in person or by proxy and entitled to vote thereat, will have the power to adjourn the meeting (subject to certain restrictions in the Merger Agreement, including that adjournment, without Assertio’s consent, must be more than five but less than 20 days after the date on which the Spectrum special meeting was originally scheduled).

Notice need not be given of the adjourned meeting if the time and place, if any, thereof and the means of remote communications, if any, by which stockholders and proxy holders may be deemed to be present in person and vote at such adjourned meeting are announced at the meeting at which the adjournment is taken or displayed, during the time scheduled for the meeting, on the same electronic network used to enable stockholders and proxy holders to participate in the meeting by means of remote communication unless the adjournment is for more than 30 days, in which case a notice of the adjourned meeting will be given to each stockholder of record entitled to vote at the meeting. If after the adjournment a new record date for the stockholders entitled to vote is fixed for the adjourned meeting, the Spectrum board of directors must fix a record date for the adjourned meeting in accordance with the DGCL and the Spectrum bylaws and provide a new notice of the adjourned meeting to each stockholder of record entitled to vote at the meeting. In addition, the Spectrum special meeting could be postponed before it commences.

If the Spectrum special meeting is adjourned or postponed for the purpose of soliciting additional votes, Spectrum stockholders who have already submitted their proxies will be able to revoke them at any

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time prior to the final vote on the proposals. If you submit your proxy over the Internet or by telephone or submit a properly executed proxy card, even if you abstain from voting, your shares will be counted as present for purposes of determining whether a quorum exists at the Spectrum special meeting.

Required Vote

You may vote “FOR,” “AGAINST,” or “ABSTAIN” with respect to the Spectrum merger proposal, the Spectrum advisory compensation proposal and the Spectrum adjournment proposal.

If a quorum is present at the Spectrum special meeting:

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approval of the Spectrum merger proposal requires the affirmative vote of the holders of a majority of the outstanding shares of Spectrum common stock entitled to vote on the proposal;

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approval of the Spectrum advisory compensation proposal requires the affirmative vote of the holders of a majority of the shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting;

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approval of the Spectrum adjournment proposal requires the affirmative vote of the holders of a majority of the shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting;

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a Spectrum stockholder’s “ABSTAIN” vote or failure to vote (including the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give any voting instructions to that bank, broker, trustee or other nominee) will have the same effect as a vote “AGAINST” the Spectrum merger proposal;

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a Spectrum stockholder’s “ABSTAIN” vote will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal and the Spectrum adjournment proposal; and

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a Spectrum stockholder’s failure to vote on the Spectrum advisory compensation proposal or the Spectrum adjournment proposal (including the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give voting instructions to its bank, broker, trustee or other nominee) will, in each case, have no effect on the Spectrum advisory compensation proposal or the Spectrum adjournment proposal.

The Merger is conditioned on, among other things, obtaining the approval of the Spectrum merger proposal at the Spectrum special meeting. Failure to return a properly executed proxy card or to vote will have the same effect as a vote “AGAINST” the Spectrum merger proposal. Broker non-votes and abstentions will have the same effect as voting “AGAINST” the Spectrum merger proposal. The Spectrum merger proposal is not conditioned on the approval of any other proposal set forth in this joint proxy statement/prospectus.

Abstentions and Broker Non-Votes

An abstention occurs when a stockholder votes “ABSTAIN.” At the Spectrum special meeting, abstentions will be counted as present for purposes of determining whether a quorum exists. “ABSTAIN” votes will have the same effect as voting “AGAINST” the Spectrum merger proposal, Spectrum advisory compensation proposal and Spectrum adjournment proposal.

If no instruction as to how to vote is given (including no instruction to abstain from voting) in an executed, duly returned and not revoked proxy, the proxy will be voted in accordance with the Spectrum board of directors’ recommendation with respect to each proposal and consequently, will be voted “FOR” each of (i) the Spectrum merger proposal, (ii) the Spectrum advisory compensation proposal and (iii) the Spectrum adjournment proposal.

Broker non-votes occur as to shares held in “street name” through a bank, broker, trustee or other nominee when (i) the bank, broker, trustee or other nominee has discretionary authority to vote on one or more proposals to be voted on at a meeting of stockholders but is not permitted to vote on other proposals without instructions from the beneficial owner of the shares and (ii) the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Under Nasdaq rules, banks, brokers and other nominees holding shares in “street name” do not have discretionary voting authority with respect to any

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of the Spectrum proposals described in this joint proxy statement/prospectus. Accordingly, if a beneficial owner of shares of Spectrum common stock held in “street name” does not give voting instructions to the bank, broker, trustee or other nominee, then those shares will not be counted as present in person or by proxy at the Spectrum special meeting and accordingly will not count as present for purposes of determining whether a quorum exists.

Therefore, assuming that a quorum is present, if you hold Spectrum common stock in “street name” and you do not instruct your bank, broker, trustee or other nominee on how to vote your shares:

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your bank, broker, trustee or other nominee may not vote your shares on the Spectrum merger proposal, which broker non-votes, if any, will have the same effect as a vote “AGAINST” such proposal; and

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your bank, broker, trustee or other nominee may not vote your shares on the Spectrum advisory compensation proposal or Spectrum adjournment proposal, which broker non-votes, if any, will have no effect for such proposal.

Failure to Vote

If you are a stockholder of record and you do not sign and return your proxy card or vote over the Internet, by telephone or at the Spectrum special meeting, your shares will not be voted at the Spectrum special meeting, will not be counted as present in person or by proxy at the Spectrum special meeting and will not be counted as present for purposes of determining whether a quorum exists.

If a quorum is present at the Spectrum special meeting:

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the failure of a Spectrum stockholder to vote on the Spectrum merger proposal (including the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give any voting instructions to that bank, broker, trustee or other nominee) will have the same effect as a vote “AGAINST” the Spectrum merger proposal; and

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the failure of a Spectrum stockholder to vote on the Spectrum advisory compensation proposal or the Spectrum adjournment proposal (including the failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give voting instructions to its bank, broker, trustee or other nominee) will have no effect on the Spectrum advisory compensation proposal or Spectrum adjournment proposal, respectively.

If you sign, date and return your proxy card and do not indicate how you want your shares of Spectrum common stock to be voted, then your shares of Spectrum common stock will be voted “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal.

Voting by Spectrum’s Directors and Executive Officers

At the close of business on June 13, 2023, directors and executive officers of Spectrum were entitled to vote 1,205,752 shares of Spectrum common stock, or approximately 0.6% of the shares of Spectrum common stock issued and outstanding on that date. Directors and executive officers of Spectrum, other than Juhyun Lim and the shares of Spectrum common stock beneficially owned by Hanmi, have informed Spectrum that they intend to vote their shares in favor of the Spectrum merger proposal, the Spectrum advisory compensation proposal and the Spectrum adjournment proposal, although none of the directors and executive officers are obligated to do so.

Voting at the Spectrum Special Meeting

The Spectrum special meeting will be a virtual-only meeting. There will be no physical meeting location and the meeting will only be conducted via live webcast. The virtual Spectrum special meeting will be held on July 27 at 10:00 a.m. Eastern Time. To participate in the Spectrum special meeting and submit questions during the Spectrum special meeting, visit www.meetnow.global/MYXFZTA and enter the 15-digit control number on the proxy card or voting instruction form you received. Online check-in will begin

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anytime after the materials are received leading up to the Spectrum special meeting. Please allow time for online check-in procedures.

The virtual stockholder meeting format uses technology designed to increase stockholder access, save Spectrum and Spectrum stockholders time and money, and provide Spectrum stockholders rights and opportunities to participate in the meeting similar to what they would have at an in-person meeting. In addition to online attendance, Spectrum provides stockholders with an opportunity to hear all portions of the official meeting, submit written questions and comments during the meeting, and vote online during the open poll portion of the meeting. Although Spectrum offers four different voting methods, Spectrum encourages you to submit a proxy to vote either over the Internet or by telephone to ensure that your shares are represented and voted at the Spectrum special meeting.

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To Submit a Proxy to Vote over the Internet: To submit a proxy to vote over the Internet, go to
https://www.envisionreports.com/SPPI and follow the steps outlined on the secured website. You will need the number included on your proxy card to obtain your records and to create an electronic voting instruction form. If you submit your proxy to vote over the Internet, you do not have to mail in a proxy card.

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To Submit a Proxy by Telephone: To submit a proxy to vote by telephone call toll-free at 1-800-652-8683 within the U.S., U.S. territories and Canada on a touch-tone telephone. Please have your proxy card available for reference because you will need the validation details that are located on your proxy card in order to submit your vote by proxy by telephone. If you submit your proxy to vote by telephone, you do not have to mail in a proxy card.

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To Submit a Proxy by Mail: To submit a proxy to vote by mail, complete, sign and date the proxy card and return it promptly to the address indicated on the proxy card in the postage paid enveloped provided. If you sign and return your proxy card without indicating how you want your shares of Spectrum common stock to be voted with regard to a particular proposal, your shares of Spectrum common stock will be voted in favor of such proposal.

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To Vote at the Spectrum special meeting: To vote at the Spectrum special meeting, follow the instructions at www.meetnow.global/MYXFZTA.

If your shares are held by your bank, broker, trustee or other nominee, you are considered the beneficial owner of shares held in “street name” and you will receive a voting instruction form from your bank, broker, trustee or other nominee seeking instruction from you as to how your shares should be voted. If you plan to attend the Spectrum special meeting, you must obtain a legal proxy from your bank, broker, trustee or other nominee that enables you to access and attend the Spectrum special meeting.

If you sign your proxy, but do not indicate how you wish to vote, your shares will be voted “FOR” the Spectrum merger proposal, “FOR” the Spectrum advisory compensation proposal and “FOR” the Spectrum adjournment proposal.

Revocation of Proxies

You can change or revoke your proxy at any time before the final vote at the Spectrum special meeting. If you are the stockholder of record of your shares, you may revoke your proxy by:

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submitting another proxy over the Internet or by telephone;

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timely delivering a written notice that you are revoking your proxy to Spectrum’s Corporate Secretary;

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timely delivering a valid, later-dated proxy; or

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attending the Spectrum special meeting and voting.

Your attendance at the Spectrum special meeting will not revoke your proxy unless you give written notice of revocation to Spectrum’s Corporate Secretary before your proxy is exercised or unless you vote your shares in person at the Spectrum special meeting.

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If you are the beneficial owner of shares held in “street name,” you should contact your bank, broker, trustee or other nominee with questions about how to change or revoke your voting instructions.

Solicitation of Proxies

The Spectrum board of directors is soliciting your proxy in connection with the Spectrum special meeting, and Spectrum will bear the cost of soliciting such proxies, including the costs of printing and filing this joint proxy statement/prospectus. Spectrum has retained Innisfree as proxy solicitor to assist with the solicitation of proxies in connection with the Spectrum special meeting. Spectrum estimates it will pay Innisfree a fee not to exceed $25,000, plus reimbursement of reasonable expenses. Spectrum has agreed to indemnify Innisfree against various liabilities and expenses that relate to or arise out of its solicitation of proxies (subject to certain exceptions). Solicitation initially will be made by mail. Forms of proxies and proxy materials may also be distributed through banks, brokers and other nominees to the beneficial owners of shares of Spectrum common stock, in which case these parties will be reimbursed for their reasonable out-of-pocket expenses. Proxies may also be solicited in person or by telephone, facsimile, electronic mail, or other electronic medium by certain of Spectrum’s directors, officers and employees, without additional compensation.

Tabulation of Votes

Computershare Trust Company, N.A. will tabulate the votes at the Spectrum special meeting.

Appraisal Rights

Pursuant to Section 262 of the DGCL, Spectrum stockholders who hold their shares through the effective time, do not vote their shares in favor of adoption of the Merger Agreement and who comply fully with and properly demand appraisal for their shares under the applicable requirements of Section 262 of the DGCL and do not otherwise withdraw or lose the right to appraisal under Delaware law, have the right to seek appraisal of the “fair value” of their shares of Spectrum common stock, as determined by the Delaware Court of Chancery, if the Merger is completed. This means that such stockholders are entitled to seek appraisal of their shares of Spectrum stock and to receive payment in cash for the “fair value” of such shares of Spectrum stock, exclusive of any element of value arising from the accomplishment or expectation of the Merger, as determined by the Delaware Court of Chancery, together with interest, if any, to be paid upon the amount determined to be the fair value. The “fair value” of shares of Spectrum common stock as determined by the Delaware Court of Chancery may be more than, less than, or equal to the value of the Merger Consideration that Spectrum stockholders would otherwise be entitled to receive under the terms of the Merger Agreement. Spectrum stockholders also should be aware that an investment banking opinion as to the fairness, from a financial point of view, of the consideration payable in a sale transaction, such as the Merger, is not an opinion as to, and does not otherwise address, “fair value” under Section 262 of the DGCL. Spectrum stockholders who wish to preserve any appraisal rights they may have must so advise Spectrum by submitting a written demand for appraisal prior to the vote to adopt the Merger Agreement and approve the transactions contemplated thereby, and must otherwise follow fully the procedures prescribed by Section 262 of the DGCL.

The text of Section 262 of the DGCL is attached as Annex F to this proxy statement/prospectus. You are encouraged to read these provisions carefully and in their entirety. Due to the complexity of the procedures for exercising appraisal rights, Spectrum stockholders who are considering exercising such rights are encouraged to seek the advice of legal counsel and their financial advisors. Failure to strictly comply with these provisions will result in the loss of appraisal rights. For additional information, please see the section titled “Appraisal Rights” beginning on page 188 of this joint proxy statement/prospectus.

IN ORDER TO PROPERLY EXERCISE YOUR APPRAISAL RIGHTS IN CONNECTION WITH THE MERGER, YOU MUST DELIVER A WRITTEN DEMAND FOR APPRAISAL IN ACCORDANCE WITH THE REQUIREMENTS OF SECTION 262 OF THE DGCL TO SPECTRUM BEFORE THE VOTE IS TAKEN ON THE ADOPTION OF THE MERGER AGREEMENT AT THE SPECIAL MEETING, AND MUST NOT VOTE, IN PERSON OR BY PROXY, IN FAVOR OF THE MERGER PROPOSAL AND CONTINUE TO HOLD YOUR SHARES OF SPECTRUM COMMON STOCK OF RECORD FROM THE DATE OF MAKING THE DEMAND FOR APPRAISAL THROUGH THE EFFECTIVE DATE OF THE MERGER AND MUST COMPLY WITH THE OTHER

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REQUIREMENTS OF SECTION 262 OF THE DGCL. MERELY VOTING AGAINST THE MERGER PROPOSAL WILL NOT PRESERVE YOUR RIGHT TO APPRAISAL UNDER SECTION 262 OF THE DGCL. BECAUSE A PROXY THAT IS SIGNED AND SUBMITTED BUT DOES NOT OTHERWISE CONTAIN VOTING INSTRUCTIONS WILL, UNLESS REVOKED, BE VOTED IN FAVOR OF THE ADOPTION OF THE MERGER AGREEMENT, IF YOU SUBMIT A PROXY AND WISH TO EXERCISE YOUR APPRAISAL RIGHTS, YOU MUST INCLUDE VOTING INSTRUCTIONS TO VOTE YOUR SHARES OF COMMON STOCK AGAINST, OR ABSTAIN WITH RESPECT TO, THE ADOPTION OF THE MERGER AGREEMENT. NEITHER VOTING AGAINST THE ADOPTION OF THE MERGER AGREEMENT, NOR ABSTAINING FROM VOTING OR FAILING TO VOTE ON THE MERGER PROPOSAL, WILL IN AND OF ITSELF CONSTITUTE A WRITTEN DEMAND FOR APPRAISAL SATISFYING THE REQUIREMENTS OF SECTION 262 OF THE DGCL. THE WRITTEN DEMAND FOR APPRAISAL MUST BE IN ADDITION TO AND SEPARATE FROM ANY PROXY OR VOTE ON THE ADOPTION OF THE MERGER AGREEMENT. IF YOU HOLD YOUR SHARES OF SPECTRUM COMMON STOCK THROUGH A BANK, BROKERAGE FIRM OR NOMINEE AND YOU WISH TO EXERCISE APPRAISAL RIGHTS, YOU SHOULD CONSULT WITH YOUR BANK, BROKERAGE FIRM OR NOMINEE TO DETERMINE THE APPROPRIATE PROCEDURES FOR THE MAKING OF A DEMAND FOR APPRAISAL BY SUCH BANK, BROKERAGE FIRM OR NOMINEE. IN VIEW OF THE COMPLEXITY OF THE DGCL, SPECTRUM STOCKHOLDERS WHO MAY WISH TO PURSUE APPRAISAL RIGHTS SHOULD PROMPTLY CONSULT THEIR LEGAL AND FINANCIAL ADVISORS.

Householding of Spectrum Special Meeting Materials

The SEC rules permit brokers to participate in a practice known as “householding,” which means that only one copy of the Notice and, if applicable, this joint proxy statement/prospectus will be sent to multiple stockholders who share the same address unless we have received contrary instructions from one or more of the stockholders. Householding is designed to reduce printing and postage costs, and results in cost savings for us. Stockholders who participate in householding will continue to be able to access and receive separate proxy cards. If you receive a householding mailing this year and would like to have additional copies of this joint proxy statement/prospectus mailed to you, or if you would like to opt out of this practice for future mailings, please contact your broker or submit your request to Spectrum’s Corporate Secretary, Keith McGahan, c/o Spectrum Pharmaceuticals, Inc., Pilot House — Lewis Wharf 2 Atlantic Avenue, 6th Floor, Boston, MA 02110 or contact Spectrum by telephone at (617) 586-3900. Upon receipt of any such request, we agree to promptly deliver a copy of this joint proxy statement/prospectus to you. In addition, if you are currently a stockholder sharing an address with another stockholder and wish to receive only one copy of future proxy materials for your household, please contact Spectrum using the contact information set forth above. This joint proxy statement/prospectus are also available at https://investor.sppirx.com/shareholder-services.

Each registered Spectrum stockholder will receive one copy of this joint proxy statement/prospectus per account, regardless of whether you have the same address as another stockholder of record. SEC rules permit companies and intermediaries such as brokers to satisfy delivery requirements for proxy statements and notices with respect to two or more stockholders sharing the same address by delivering a single proxy statement or a single notice addressed to those stockholders. This process, commonly called “householding,” provides cost savings for companies. Some brokers household proxy materials, delivering a single proxy statement or notice to multiple stockholders sharing an address unless contrary instructions have been received from the affected stockholders. For more details, see the section titled “Householding of Proxy Materials” beginning on page 198 of this joint proxy statement/prospectus.

Questions

If you have more questions about the Merger or how to submit your proxy, or if you need additional copies of this joint proxy statement/prospectus or the enclosed proxy card or voting instructions, please contact Spectrum’s Corporate Secretary at (617) 586-3900, or write to Spectrum’s Corporate Secretary at Spectrum’s principal executive offices at Pilot House — Lewis Wharf 2 Atlantic Avenue, 6th Floor Boston, MA 02110.

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Assistance

If you need assistance voting or in completing your proxy card or have questions regarding the Spectrum special meeting, please contact the Spectrum solicitation agent:

Innisfree M&A Incorporated
501 Madison Avenue, 20th Floor
New York, NY 10022
Stockholders May Call: (877) 800-5185 (toll-free from the U.S. and Canada)
Banks and Brokers May Call: (212) 750-5833

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SPECTRUM PROPOSAL 1: THE SPECTRUM MERGER PROPOSAL

This joint proxy statement/prospectus is being furnished to Spectrum stockholders as part of the solicitation of proxies by the Spectrum board of directors for use at the Spectrum special meeting to consider and vote upon a proposal to adopt the Merger Agreement, which is attached as Annex A to this joint proxy statement/prospectus, and approve the transactions contemplated thereby, including the Merger.

The Spectrum board of directors, after due and careful discussion and consideration, (i) determined that the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement are fair and in the best interest of, and are advisable to, Spectrum and the Spectrum stockholders, (ii) approved and adopted the Merger Agreement and approved the Merger and the other transactions contemplated by the Merger Agreement and (iii) recommended that the Spectrum stockholders approve the Merger Agreement.

Required Vote of Stockholders

The Spectrum board of directors accordingly recommends that Spectrum stockholders vote “FOR” the proposal to adopt the Merger Agreement, as disclosed in this joint proxy statement/prospectus, particularly the related narrative disclosures in the sections of this joint proxy statement/prospectus titled “The Merger” and “The Merger Agreement” beginning on pages 71 and 127, respectively, and as attached as Annex A to this joint proxy statement/prospectus.

Obtaining approval of the Spectrum merger proposal is a condition to consummation of the Merger.

The vote on the Spectrum merger proposal is a vote separate and apart from the vote to approve either the Spectrum advisory compensation proposal or the Spectrum adjournment proposal. Accordingly, a Spectrum stockholder may vote to approve the Spectrum merger proposal and vote not to approve the Spectrum advisory compensation proposal or the Spectrum adjournment proposal, and vice versa.

Assuming that a quorum is present, the approval of the Spectrum merger proposal requires the affirmative vote of holders of a majority of the outstanding shares of Spectrum common stock entitled to vote on the proposal. A failure to vote (including a failure to instruct your bank, broker, trustee or other nominee to vote) or an abstention will have the same effect as a vote “AGAINST” the Spectrum merger proposal.

THE SPECTRUM BOARD OF DIRECTORS RECOMMENDS THAT YOU VOTE “FOR” THE SPECTRUM MERGER PROPOSAL

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SPECTRUM PROPOSAL 2: THE SPECTRUM ADVISORY COMPENSATION PROPOSAL

Pursuant to Section 14A of the Exchange Act, Spectrum is asking Spectrum stockholders to approve, on an advisory (non-binding) basis, the compensation that will or may be paid to Spectrum’s named executive officers in connection with the Merger as described in the section titled “Interests of Spectrum’s Directors and Executive Officers in the Merger” beginning on page 168 of this joint proxy statement/prospectus. The Spectrum advisory compensation proposal gives Spectrum stockholders the opportunity to express their views on the Merger-related compensation of Spectrum’s named executive officers.

Required Vote of Stockholders

Spectrum is asking Spectrum stockholders to vote “FOR” the adoption of the following resolution, on a non-binding advisory basis:

“RESOLVED, that the compensation that may be paid or become payable to the named executive officers of Spectrum that is based on or otherwise relates to the Merger, as disclosed pursuant to Item 402(t) of Regulation S-K under the section “Interests of Spectrum’s Directors and Executive Officers in the Merger” beginning on page 168 of this joint proxy statement/prospectus, including the associated narrative discussion, and the agreements, plans and other arrangements pursuant to which such compensation may be paid or become payable, be, and are hereby APPROVED.”

Because the vote on the Spectrum advisory compensation proposal is advisory only, it will not be binding on either Spectrum or Assertio. Accordingly, if the Spectrum merger proposal is approved and the Merger is consummated, the Merger-related compensation will be payable to Spectrum’s named executive officers, subject only to the conditions applicable thereto, regardless of the outcome of the approval of the Spectrum advisory compensation proposal.

Assuming a quorum is present, approval of the Spectrum advisory compensation proposal requires the affirmative vote of the holders of a majority of the shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting. Accordingly, for Spectrum stockholders of record who are not present in person or represented by proxy at the Spectrum special meeting and for beneficial owners who fail to instruct their bank, broker, trustee or other nominee to vote on the Spectrum advisory compensation proposal, a failure to vote will have no effect on the outcome of the vote for the Spectrum advisory compensation proposal. All abstentions will have the same effect as a vote “AGAINST” the Spectrum advisory compensation proposal.

The vote on the Spectrum advisory compensation proposal is a vote separate and apart from the vote to approve either the Spectrum merger proposal or the Spectrum adjournment proposal. Accordingly, a Spectrum stockholder may vote to approve the Spectrum advisory compensation proposal and vote not to approve the Spectrum merger proposal or the Spectrum adjournment proposal, and vice versa.

THE SPECTRUM BOARD OF DIRECTORS RECOMMENDS THAT YOU VOTE “FOR” THE SPECTRUM ADVISORY COMPENSATION PROPOSAL

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SPECTRUM PROPOSAL 3: THE SPECTRUM ADJOURNMENT PROPOSAL

The Spectrum special meeting may be adjourned to another time and place, including, if necessary to permit solicitation of additional proxies if there are not sufficient votes to approve the Spectrum merger proposal or to ensure that any supplemented or amended disclosure, including any supplement or amendment to this joint proxy statement/prospectus, is timely provided to Spectrum stockholders.

Spectrum is asking Spectrum stockholders to authorize the holder of any proxy solicited by the Spectrum board of directors to vote in favor of any adjournment of the Spectrum special meeting to solicit additional proxies if there are not sufficient votes to approve the Spectrum merger proposal or to ensure that any supplemental or amended disclosure, including any supplement or amendment to this joint proxy statement/prospectus, is timely provided to Spectrum stockholders.

Required Vote of Stockholders

The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” the proposal to adjourn the Spectrum special meeting, if necessary.

Assuming a quorum is present at the Spectrum special meeting, approval of the Spectrum adjournment proposal requires the affirmative vote of the holders of a majority of the shares of Spectrum common stock present in person or represented by proxy and entitled to vote thereon at the Spectrum special meeting. Accordingly, a failure to vote on the Spectrum adjournment proposal by a Spectrum stockholder of record who is not present in person or represented by proxy at the Spectrum special meeting or a failure of a Spectrum stockholder who holds shares in “street name” through a bank, broker, trustee or other nominee to give voting instructions to its bank, broker, trustee or other nominee on the Spectrum adjournment proposal will, in each case, have no effect on the Spectrum adjournment proposal.

All abstentions will have the same effect as a vote “AGAINST” the Spectrum adjournment proposal.

The vote on the Spectrum adjournment proposal is a vote separate and apart from the vote to approve the Spectrum merger proposal or the Spectrum advisory compensation proposal. Accordingly, a Spectrum stockholder may vote to approve the Spectrum adjournment proposal and vote not to approve the Spectrum merger proposal or the Spectrum advisory compensation proposal, and vice versa.

THE SPECTRUM BOARD OF DIRECTORS RECOMMENDS THAT YOU VOTE “FOR” THE SPECTRUM ADJOURNMENT PROPOSAL

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THE MERGER

The following is a description of material aspects of the Merger. While Assertio and Spectrum believe that the following description covers the material terms of the Merger, the description may not contain all of the information that is important to you. You are encouraged to read carefully this entire joint proxy statement/prospectus, including the text of the Merger Agreement attached as Annex A hereto, for a more complete understanding of the Merger. In addition, important business and financial information about each of Assertio and Spectrum is contained or incorporated by reference in this joint proxy statement/prospectus. See “Where You Can Find More Information.”

General

Assertio, Merger Sub and Spectrum have entered into the Merger Agreement, which provides for the Merger of Merger Sub with and into Spectrum. As a result of the Merger, the separate existence of Merger Sub will cease and Spectrum will continue its existence under the DGCL as the surviving corporation and as a wholly owned subsidiary of Assertio. The surviving corporation will be named “Spectrum Pharmaceuticals, Inc.”

Merger Consideration

At the effective time, each share of Spectrum common stock (other than (i) shares held in treasury by Spectrum or held directly by Assertio or Merger Sub, which shares will be cancelled) or (ii) shares that are held by any holder who is entitled to demand and properly demands appraisal of such Spectrum shares of Spectrum common stock pursuant to, and in compliance with, Section 262 of the DGCL) that was issued and outstanding immediately prior to the effective time will be converted into (A) the right to receive 0.1783 of a fully paid and non-assessable share of common stock, par value $0.0001 per share, of Assertio, and, if applicable, cash in lieu of fractional shares (without interest and less any applicable withholding taxes), and (B) one CVR per share.

The exchange ratio is fixed, which means that it will not change between now and the date of the Merger, regardless of whether the market price of Assertio or Spectrum common stock changes. Therefore, the value of the Merger Consideration will depend on the market price of Assertio common stock at the effective time. The market price of Assertio common stock has fluctuated since the date of the announcement of the Merger Agreement and is expected to continue to fluctuate from the date of this joint proxy statement/prospectus to the dates of the respective Assertio and Spectrum special meetings, through the date the Merger is completed and thereafter. The market price of Assertio common stock, when received by Spectrum stockholders in connection with the Merger, could be greater than, less than or the same as the market price of Assertio common stock on the date of this joint proxy statement/prospectus or at the time of the Spectrum special meeting. Accordingly, you should obtain current market quotations for Assertio and Spectrum common stock before deciding how to vote on any of the proposals described in this joint proxy statement/prospectus. Assertio common stock is traded on Nasdaq SM under the symbol “ASRT” and Spectrum common stock is traded on Nasdaq CM under the symbol “SPPI.”

Background of the Merger

The Spectrum board of directors, together with members of Spectrum senior management, regularly reviews and assesses the performance, future growth prospects, business plans and overall strategic direction of Spectrum. The Spectrum board of directors has also, on a regular basis, considered a variety of strategic alternatives that may be available to Spectrum, including continuing as a standalone company or pursuing potential strategic or financing transactions with third parties, in each case with the goal of maximizing stockholder value.

Following the appointment of Thomas J. Riga as Spectrum’s President and Chief Executive Officer effective January 1, 2022, the Spectrum board of directors engaged in discussions regarding potential strategic alternatives at each of its regularly scheduled meetings and authorized Mr. Riga and the Spectrum management team to explore potential strategic alternatives. Based on the near-term regulatory milestones for Spectrum’s two late-stage assets, ROLVEDON and poziotinib, the timing of this direction was intended to

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provide Spectrum with maximum optionality given the broad range of potential outcomes from pending regulatory actions of the U.S. Food and Drug Administration (“FDA”).

On January 1, 2022 Spectrum and Hanmi Pharmaceutical Co. Ltd. (“Hanmi”) entered into that certain Second Amendment to the Supply Agreement dated February 28, 2018 (as amended, the “Supply Agreement”) setting forth the revised terms pursuant to which Hanmi would continue to act as the sole manufacturer and supplier of the ROLVEDON drug substance. The Supply Agreement contemplates fixed pricing terms for three years following initial commercialization of ROLVEDON, through the latter half of 2025 and does not include any “change of control” provisions that would be implicated by a sale of Spectrum. On January 3, 2022, Spectrum and Hanmi, in connection with their discussions around the Supply Agreement, entered into a Securities Purchase Agreement, pursuant to which Hanmi’s ownership of shares of Spectrum common stock increased to 8.7% of the total outstanding shares (which has since been diluted to approximately 7.5% of the total outstanding shares) and obtained the right to appoint a designee to the Spectrum board of directors for so long as Hanmi beneficially owns at least 5% of the outstanding shares of Spectrum common stock. Hanmi designated Juhyun Lim, who remains Hanmi’s designee and a member of the Spectrum board of directors.

During the spring and summer of 2022, members of the senior management of Spectrum, under the supervision of the Spectrum board of directors, engaged in a series of additional exploratory discussions with a range of pharmaceutical companies. The objective of these discussions was to gauge interest in an acquisition of or strategic combination with Spectrum, with the goal of maximizing stockholder value. Given the pending regulatory action from the FDA on Spectrum’s two leading development assets, ROLVEDON and poziotinib, the Spectrum board of directors determined that it was unlikely that potential counterparties would be willing to transact ahead of such actions, and consequently decided not to initiate a broad proactive outreach to potential strategic counterparties until the FDA provided clarity on both assets.

In the summer of 2022, in connection with the Spectrum board of directors’ discussions of strategic alternatives, Ms. Lim, who was then-President, Global Strategy and Planning of Hanmi in addition to being a member of the Spectrum board of directors, approached Mr. Riga regarding Hanmi’s potential interest in pursuing a strategic transaction with Spectrum. Ms. Lim and Mr. Riga conducted high-level discussions with respect to the potential benefits and challenges of a strategic transaction, but no proposal was ever made to Spectrum by or on behalf of Hanmi.

The Assertio board of directors considers business development opportunities on a regular basis and reviews such opportunities at its regularly scheduled board meetings. Consistent with this approach, the Assertio board of directors discussed potential transactions at each of its quarterly board meetings in 2022. Pursuant to the Assertio board of directors’ standing instruction, Assertio management was authorized to pursue appropriate opportunities consistent with the board’s guidance on a preliminary basis, including by making preliminary indications of interest with respect to asset acquisitions without pre-approval by the Assertio board of directors.

On July 28, 2022, the Assertio board of directors engaged SVB Securities LLC (“SVB Securities”) in connection with exploring such potential business development transactions. The Assertio board of directors selected SVB Securities to act as Assertio’s non-exclusive financial advisor based on SVB Securities’ qualifications, reputation, experience and expertise in the biopharmaceutical industry, its knowledge of and involvement in recent transactions in the biopharmaceutical industry and its relationship and familiarity with Assertio and its business.

On September 9, 2022, Spectrum received the FDA’s marketing approval for ROLVEDON and immediately initiated commercialization activities.

On September 22, 2022, Spectrum announced that the FDA’s Oncologic Drugs Advisory Committee (the “ODAC”) determined that the current benefits of poziotinib for the treatment of patients with previously treated locally advanced or metastatic non-small cell lung cancer harboring HER2 exon 20 insertion mutations did not outweigh its risks. Spectrum subsequently received a complete response letter from the FDA indicating that poziotinib would not be approved in its then-current form. As a result, Spectrum deprioritized the poziotinib development program and focused its resources on the successful commercialization of ROLVEDON. Between September 19, 2022 and September 23, 2022, Spectrum’s closing share price fell from $1.06 per share to $0.43 per share, an approximately 60% drop during such period.

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In late September 2022, following the ODAC recommendation, the Spectrum board of directors selected Guggenheim Securities, LLC (“Guggenheim Securities”) as its financial advisor in connection with Spectrum’s continued exploration of a potential sale, merger, or other extraordinary corporate transaction. The Spectrum board of directors selected Guggenheim Securities as its financial advisor because of its significant expertise in the biopharmaceutical industry and its familiarity with Spectrum and its business, including having previously represented Spectrum in connection with certain strategic initiatives.

Starting in the fall of 2022, Spectrum and Guggenheim Securities engaged with over 40 counterparties, of which 14 counterparties entered into non-disclosure and standstill agreements with Spectrum and conducted due diligence on Spectrum.

On October 22, 2022, and December 5, 2022, the Spectrum board of directors met to discuss, among other things, updates with respect to the process and the options presented to Spectrum for potential fundamental transactions, including a merger or a sale of the company and directed Guggenheim Securities to solicit indications of interest from various interested parties.

On November 28, 2022, a representative of SVB Securities introduced members of the Assertio senior management team to members of the Spectrum senior management team. Spectrum and Guggenheim Securities subsequently held an initial introductory meeting with members of Assertio’s senior management to discuss a potential transaction. Thereafter, Spectrum and Assertio entered into a non-disclosure agreement effective November 30, 2022. Counterparties under non-disclosure agreements were granted access to a virtual data room.

During the fall of 2022, Ms. Lim noted, in discussions with Mr. Riga and Mr. Ashton, that she was continuing to evaluate a potential strategic transaction between Hanmi and Spectrum.

In the first week of December 2022, Ms. Lim informed the Spectrum board of directors that she would be recusing herself from future board meetings regarding strategic alternatives in light of any actual or potential conflicts of interest due to Hanmi’s ownership and commercial interests in Spectrum. As a result, Ms. Lim did not participate in the December 5, 2022 meeting or any subsequent meetings of the Spectrum board of directors through the signing of the Merger Agreement with Assertio on April 24, 2023. However, William Ashton, the Chairman of the Spectrum board of directors, and Mr. Riga continued to engage in periodic updates and discussions with representatives of Hanmi, including Ms. Lim, to keep them apprised of progress regarding Spectrum’s pursuit of strategic alternatives.

On December 15, 2022, Assertio’s senior management team sent Spectrum a list of proposed discussion topics with respect to preliminary commercial diligence, which Assertio’s senior management team discussed at a subsequent meeting on December 16, 2022, with Spectrum and SVB Securities.

On January 6, 2023, Spectrum received, through its financial advisors, a preliminary non-binding indication of interest to acquire Spectrum from a potential strategic partner (“Party A”), which was an all-stock proposal that valued Spectrum at $0.55 per share. In addition, Spectrum received a non-binding proposal from Assertio, through its financial advisors, on January 19, 2023 to acquire Spectrum’s ROLVEDON asset for an upfront purchase price of $60 million in cash and earnouts of up to $210 million, based on sales-based milestones, which represented an upfront consideration that was less than Spectrum’s equity value of approximately $115 million as of January 19, 2023.

During the J.P. Morgan Healthcare Conference (January 9-12, 2023), members of Hanmi’s Business Development team, at the direction of Ms. Lim, indicated to Spectrum that Hanmi was unlikely to engage in a strategic transaction with Spectrum in the near-term given organizational changes and a modification of strategic priorities at Hanmi. However, Ms. Lim requested that Hanmi continue to receive access to the Spectrum virtual data room in order to maintain optionality.

On January 31, 2023, Spectrum announced the expected ROLVEDON net sales for the first partial quarter of launch and following such announcement the Spectrum stock price rose approximately 50% to $0.81 per share by February 3, 2023. In February 2023, Spectrum directed Guggenheim Securities to update counterparties on ROLVEDON’s progress, which included contacting Assertio, and the majority of the other counterparties contacted since September 2022 and solicit revised indications of interest based on

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recent sales results. As part of these discussions, Guggenheim Securities advised SVB Securities, that given ROLVEDON’s status as Spectrum’s only major value driver, Spectrum’s focus was on a full equity acquisition of Spectrum.

On February 6, 2023, the CEO of another strategic counterparty (“Party B”) held a discussion with representatives of Spectrum to learn more about the process. On February 10, 2023, the CEO of Party B connected with Mr. Riga, affirming Party B’s intention to submit a proposal to acquire Spectrum following Party B’s initial diligence of Spectrum’s business and operations.

On February 13, 2023, the Assertio board of directors held a regular meeting, with Assertio’s senior management team present, to discuss the details of a potential strategic transaction with Spectrum. Among other things, the Assertio board of directors reviewed management’s initial commercial diligence findings and Spectrum’s business generally, including ROLVEDON’s early commercial success and Spectrum’s litigation profile. Based on these discussions, the Assertio board of directors authorized Assertio’s management team to continue engaging Spectrum with respect to a potential transaction, including sending a revised indication of interest.

On February 18, 2023, following discussions with the Assertio board of directors, Assertio’s senior management team, through SVB Securities, made a cash and stock proposal to acquire Spectrum which valued Spectrum at $1.05 per share.

On February 21, 2023, Party A made an all-stock proposal that valued Spectrum at approximately $0.99 per share in upfront consideration and included a contingent value right (“CVR”) to receive shares of common stock of the combined company that would be issued to Party A’s shareholders based upon the timing and nature of obtaining certain regulatory approvals relating to a drug in Party A’s development pipeline as well as a CVR to receive shares of common stock of the combined company that would be issued to Spectrum’s stockholders if such approvals were not obtained within 24 months following the closing of the proposed transaction, which CVRs could have resulted in Spectrum stockholders holding between approximately 19% and 64% of the combined company.

On February 22, 2023, the Spectrum board of directors held a virtual meeting at which certain representatives of Spectrum senior management, Guggenheim Securities and Gibson, Dunn & Crutcher LLP, outside legal counsel to Spectrum (“Gibson Dunn”), were present for all or a portion of such meeting. A representative of Gibson Dunn reviewed and discussed the Spectrum board of directors’ fiduciary duties in the context of Spectrum’s review of strategic alternatives. A representative of Guggenheim Securities presented an overview of each of the parties that had submitted or were anticipated to submit a proposal, including Party A, Party B and Assertio, and reviewed the advantages and disadvantages of each potential counterparty and their respective proposals (or anticipated proposals), including that Party B had not previously consummated a significant strategic transaction. Given the all-stock aspect of Party A’s proposal and the significant uncertainty regarding the approval of a drug in its development pipeline, the Spectrum board of directors determined to delay engagement with Party A until greater regulatory clarity was available with respect to such development candidate. The Spectrum board of directors instructed Spectrum management to further engage with Party B and Assertio and instructed Gibson Dunn to prepare an initial draft of a merger agreement to be sent to these and any other potential counterparties.

On February 23, 2023, Guggenheim Securities sent a process letter to Assertio and on March 2, 2023 Guggenheim Securities sent a process letter to Party B, in each case requesting a revised non-binding indication of interest and markup of the Merger Agreement by March 13, 2023.

On February 24, 2023, Spectrum’s management held a discussion with representatives of Party B to provide an update on Spectrum’s business and respond to diligence questions.

On February 24, 2023, Gibson Dunn, on behalf of Spectrum, sent an initial draft of the Merger Agreement for the proposed transaction to Latham & Watkins LLP (“Latham”), outside counsel to Assertio. Such initial draft included, among other terms, (i) that an unspecified number of members of the Spectrum board of directors would join the Assertio board of directors in connection with the consummation of the transaction, (ii) a “hell or high water” regulatory efforts covenant and (iii) “fiduciary out” provisions for both parties, with the amount of termination fees left blank.

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On February 28, 2023, Assertio’s senior management team held a meeting with SVB Securities, Spectrum and Guggenheim Securities to discuss outstanding commercial diligence questions related to Spectrum’s business.

On March 1, 2023, Party B made an all-cash proposal that valued Spectrum at $1.01 per share in upfront consideration and total potential consideration of $1.31 per share, including potential CVR payments to Spectrum stockholders.

Later on March 1, 2023, the Spectrum board of directors held a virtual meeting to discuss Assertio’s February 18, 2023 proposal and Party B’s March 1, 2023 proposal.

On March 2, 2023, Gibson Dunn, on behalf of Spectrum, sent an initial draft of a merger agreement for a proposed strategic transaction with Party B to Party B’s counsel.

On March 3, 2023, Spectrum and its advisors received invitations to Assertio’s virtual data room and Spectrum initiated due diligence with respect to Assertio, in light of the stock-based component of its proposal, across multiple functional groups, including legal, longevity of portfolio, finance, tax, commercial, market access, manufacturing & controls, quality, regulatory, clinical, human resources, medical affairs and information technology. Spectrum, with the assistance of its legal advisor and industry consultants, conducted due diligence of Assertio through the eventual signing of the Merger Agreement. Also on March 3, 2023, Assertio’s senior management team, together with its outside advisors held meetings with Spectrum and its advisors to discuss outstanding commercial diligence questions related to Spectrum’s business, as well as certain pending securities litigation and related derivative actions with respect to Spectrum’s business.

Between March 6, 2023, and March 9, 2023, Assertio, Spectrum and their respective advisors conducted several due diligence calls pertaining to tax, finance, IP, legal, manufacturing & controls, HR and commercial diligence as well as a follow up discussion related to pending securities litigation and related derivative actions. During this period, Spectrum and its advisors also continued to engage in due diligence with respect to Assertio. On March 9, 2023 Spectrum’s senior management team together with its advisors and Assertio’s senior management team met to discuss an overview of Assertio’s business.

On March 7, 2023, the Assertio senior management team discussed updates to the transaction with SVB Securities, including that Assertio was willing to grant Spectrum the right to designate one director to Assertio’s board of directors following the closing of the proposed transaction.

Between March 8 and March 13, 2023, Party B and Spectrum conducted several due diligence calls pertaining to supply chain, quality, manufacturing & controls, legal & IP, finance, HR, securities litigation, tax, commercialization and IT diligence.

On March 9, 2023, the Spectrum board of directors held a virtual meeting to discuss updates in respect of the sale process at which certain representatives of Spectrum senior management, Guggenheim Securities and Gibson Dunn were present for all or a portion of such meeting. Spectrum senior management reviewed with the Spectrum board of directors the Spectrum Projections, which they believed Spectrum would achieve. The Spectrum board of directors approved such Spectrum Projections and authorized them to be shared with Assertio and Party B. A representative of Guggenheim Securities described bidder engagement since the prior March 1, 2023 meeting of the Spectrum board of directors and the offers received from Party B and Assertio. Next, a representative of Guggenheim Securities reviewed discussions with Party B and Assertio regarding requested improvements to their respective offers, as well as financing considerations relating to Assertio’s offer and potential synergies that were discussed with Party B. The Guggenheim Securities representative noted that both parties had conducted substantial due diligence and were working on revised proposals.

On March 13, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives of SVB Securities to discuss its ongoing diligence efforts in respect of the proposed transaction. In particular, the Assertio senior management team discussed (i) certain securities class action litigation and related derivative suits pending with respect to the Spectrum business and (ii) the status of ongoing commercial diligence with respect to Spectrum. The Assertio board of directors also determined that it would be prudent to engage an additional financial advisor with respect to the proposed transaction and directed Assertio’s senior management team to do so.

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Following the meeting of Assertio’s board of directors, Assertio’s management engaged Wainwright to act as a financial advisor to the Assertio board of directors and to provide a second fairness opinion with respect to the proposed transaction. Assertio selected Wainwright due to its qualifications, reputation, experience and expertise in the biopharmaceutical industry, its knowledge of and involvement in recent transactions in the biopharmaceutical industry, its relationship and familiarity with Assertio and its business and its ability to provide a fairness opinion on the required timeline.

Also following the March 13, 2023 meeting of the Assertio board of directors, at the board’s direction, Assertio’s senior management team drafted a letter to Mr. Riga informing him that Assertio would be withdrawing its February 18, 2023 proposal, because, among other reasons, the requested timeline for a revised bid would not allow sufficient time for Assertio to obtain financing, and instead intended to submit a revised all-stock proposal by March 20, 2023. Guggenheim Securities separately relayed this update to Spectrum’s senior management and board of directors.

Also on March 13, 2023, Latham, on behalf of Assertio, delivered to Gibson Dunn a revised draft of the Merger Agreement for the proposed transaction, which draft contemplated, among other terms, (i) a reduced regulatory efforts standard (with no reverse termination fee or other remedy associated with a failure to obtain regulatory approvals), (ii) certain disclosure and non-solicitation requirements related to any third party acquisition proposals that may be received by Spectrum or Assertio and (iii) a requirement that Hanmi deliver a voting and support agreement with respect to the proposed transaction.

On March 15, 2023, Party B informed Guggenheim Securities that in order to finalize a proposal and enter into a transaction, it would require certain additional diligence items. Also on March 15, 2023, Assertio’s senior management team and its advisors held a meeting with Spectrum and its advisors to discuss diligence questions related to Spectrum’s business.

Later on March 15, 2023, Mr. Riga, Mr. Ashton and Ms. Lim had a conversation, in which Ms. Lim informed Mr. Riga and Mr. Ashton that, as representatives of Hanmi had previously indicated, Hanmi would not be submitting a bid to engage in a strategic transaction with Spectrum in light of Hanmi’s recent organizational changes and modification of strategic priorities. However, to forestall any potential or actual conflicts of interest arising from Hanmi’s various interests in Spectrum, Ms. Lim reiterated she would continue to recuse herself from future board meetings regarding strategic alternatives.

On March 16, 2023, Spectrum provided to Party B a schedule setting forth the timing of responses to Party B’s diligence requirements. Spectrum informed Party B that Spectrum’s efforts to meet such schedule were contingent on Party B delivering an updated proposal and the imminence of an agreed upon transaction between Spectrum and Party B.

On March 17, 2023, Party B’s counsel, on behalf of Party B, delivered to Gibson Dunn a revised draft of the merger agreement for a proposed transaction.

On March 19, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives of Latham, Wilmer Cutler Pickering Hale and Dorr LLP (“Wilmer Hale”), Assertio’s litigation counsel, SVB Securities, Wainwright, and certain other advisors. Assertio’s senior management and Latham provided an update on the status of negotiations with Spectrum’s management team regarding the proposed transaction, including the proposed terms contained in the latest draft of the Merger Agreement. Assertio’s senior management, Latham and Wilmer Hale provided an update as to ongoing commercial, legal and financial diligence. Latham additionally provided the Assertio board of directors with an overview of its fiduciary duties under Delaware law, both in general and in the context of the proposed transaction. Representatives from SVB Securities also provided an overview of the Spectrum Projections. Following a discussion on these and related topics, the Assertio board of directors authorized management to submit a revised non-binding indication of interest consisting of (i) upfront consideration of $1.00 per share in Assertio common stock, (ii) CVR payments (payable in stock or cash at Assertio’s election) with (x) a milestone payment equal to $0.15 per CVR in the event net revenue of ROLVEDON during calendar year 2024 exceeds $175 million and (y) a milestone payment equal to $0.20 per CVR in the event net revenue of ROLVEDON during calendar year 2025 exceeds $225 million, resulting in total potential consideration of up to $1.35 per share and (iii) a termination fee of up to 3.5% of the transaction value. Assertio subsequently submitted a revised all-stock, non-binding proposal to Spectrum,

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which was consistent with the terms approved by the Assertio board of directors (the “March 19 Proposal”). Assertio also indicated to Spectrum that it had completed substantially all of its due diligence and was prepared to finalize the negotiations and announce the transaction concurrently with the announcement of Spectrum’s fourth quarter 2022 earnings, scheduled for March 22, 2023. In response, Spectrum indicated to Assertio that the upfront consideration would need to be improved to $1.20 per share in order for Spectrum to agree to the proposed transaction.

On March 20, 2023, Latham, on behalf of Assertio, delivered to Gibson Dunn a further revised draft of the Merger Agreement and a draft of the CVR Agreement, which reflected the terms of the March 19 Proposal.

On March 21, 2023, Party B re-submitted a proposal on the same financial terms as its original proposal, which included an all-cash proposal valuing Spectrum at $1.01 per share in upfront consideration and total potential consideration of $1.31 per share, including potential CVR payments. Following discussion among Guggenheim Securities, Mr. Riga and Mr. Ashton, and upon the instruction of Spectrum management, Guggenheim Securities responded to Party B on behalf of Spectrum that in order to progress towards a potential transaction and receive access to additional diligence materials, the upfront consideration would need to be increased.

On March 22, 2023, Spectrum announced its fourth quarter 2022 earnings, including sales in connection with the launch of ROLVEDON commercialization. The Spectrum share price fell from $0.83 per share on March 21, 2023, to $0.71 per share on March 23, 2023.

Also on March 22, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives from SVB Securities and Wainwright. The Assertio board of directors discussed Spectrum’s Q4 2022 earnings release and the market response, as well as Spectrum’s request to increase the upfront purchase price to $1.20 per share. The Assertio board of directors directed Assertio management and SVB Securities to communicate to Spectrum that Assertio would not increase its upfront consideration to $1.20 per share.

On March 23, 2023, Assertio indicated to Spectrum that it would not increase the upfront consideration component of its proposal to $1.20 per share.

On March 24, 2023, Party B submitted an updated all-cash proposal consisting of upfront consideration of $1.05 per share in cash, plus potential all-cash CVR payments, for total potential consideration of up to $1.31 per share.

Later on March 24, 2023, the Spectrum board of directors held a virtual meeting, at which certain representatives of Spectrum senior management, Gibson Dunn and Guggenheim Securities were present for all or a portion of such meeting, to discuss, among other things, Spectrum’s stock price performance since the fourth quarter 2022 earnings announcement and updates with respect to the sale process. Representatives of Guggenheim Securities updated the Spectrum board of directors regarding Assertio’s indication that it would not increase the upfront consideration of its proposal, while Party B indicated it needed to conduct further diligence on Spectrum. The Spectrum board of directors discussed these proposals in light of the fact that Spectrum’s stock price had traded down since the earnings release. The Spectrum board of directors and management then discussed the advantages and disadvantages of pursuing a strategic transaction with either Assertio or Party B in contrast to pursuing a standalone strategy and the risks of continuing to engage, including that Party B’s additional diligence requests would be burdensome on the Spectrum management team and there was execution risk in Party B’s proposal given their lack of experience in strategic transactions. Nevertheless, the Spectrum board of directors determined that it was in the best interests of the Spectrum stockholders for Spectrum management to continue negotiating with each of Assertio and Party B in pursuit of a potential strategic transaction. As such, the Spectrum board of directors instructed Spectrum management to accommodate Party B with respect to its diligence requests and to provide Assertio additional time to make a revised offer.

Over the week of March 26, 2023, Spectrum and Party B conducted additional diligence.

On March 29, 2023, SVB Securities indicated to Guggenheim Securities that Assertio remained interested in engaging in further discussions at an offer price below $1.20 per share.

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On March 30, 2023, Assertio’s senior management team corresponded with Assertio’s board of directors regarding a revised proposal consisting of increased upfront consideration of $1.10 per share in Assertio common stock, with reduced CVR payments (payable in stock or cash at Assertio’s election), maintaining the total potential consideration of $1.35 per share, which the Assertio board of directors authorized on March 31, 2023, and which Assertio subsequently submitted to Spectrum that day. As part of this proposal, Assertio requested exclusivity through April 10, 2023, but Spectrum, wishing to continue to negotiate with each of Assertio and Party B, did not agree to such request.

On April 2, 2023, members of Assertio’s senior management team and Spectrum’s senior management team discussed, among other things, updates with respect to Spectrum’s revenue in the first quarter of 2023, Spectrum’s ongoing reverse due diligence efforts and possible exclusivity between the parties. Additionally, Spectrum’s senior management team indicated that a revised proposal of $1.15 per share may be sufficient for the Spectrum board of directors to move forward with the transaction.

Later on April 2, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives from SVB Securities. The Assertio board of directors discussed with SVB Securities potential changes to the upfront per share purchase price, and authorized Assertio management to submit an updated proposal consisting of upfront consideration of $1.15 per share of Assertio common stock, with CVR payments (payable in stock or cash at Assertio’s election) bringing the total potential consideration to $1.30 per share. Also on April 2, 2023, Gibson Dunn, on behalf of Spectrum, delivered to Latham a revised draft of the Merger Agreement for the proposed transaction, continuing to negotiate the terms of the regulatory efforts and related remedies and leaving the termination fee blank. On April 4, 2023, Gibson Dunn, on behalf of Spectrum, delivered to Latham a revised draft of the form of CVR Agreement, which draft contemplated, among other terms, (i) revised measurement periods for the milestone payments from the calendar years 2024 and 2025, respectively, to any consecutive 12-month period ending before December 31, 2024 or December 31, 2025, respectively, (ii) expanding the scope of the sales milestones related to the CVR payments to encompass products resulting from the combination of ROLVEDON with other drug substances (a “Combination Product”) and (iii) requiring that Assertio use a defined level of efforts to achieve the ROLVEDON sales milestones relating to the 2024 and 2025 milestone payments.

Between April 4, 2023, and April 5, 2023, Assertio’s senior management team held meetings with its advisors (including SVB Securities, Latham and certain other advisors), and Spectrum and its advisors (including Guggenheim Securities, Gibson Dunn and certain other advisors), to discuss various tax, manufacturing, quality assurance, regulatory, employment and legal diligence matters. Additionally, between April 4, 2023, and April 5, 2023, Assertio’s senior management team held meetings with its advisor, SVB Securities, Spectrum and the parties’ respective legal advisors, to discuss various financial diligence matters and revenue projections, along with certain commercial and marketing diligence matters.

Also on April 5, 2023, Mr. Riga and Daniel Peisert, President and Chief Executive Officer of Assertio, met to discuss the status of ongoing negotiations and diligence.

Further on April 5, 2023, Party B submitted an updated all-cash proposal consisting of upfront consideration of $1.05 per share, with CVR payments bringing the total potential consideration to $1.46 per share. Spectrum management communicated to Party B that in order for Spectrum to move forward with Party B, it would need to increase the upfront consideration.

On April 6, 2023, Party B submitted an updated all-cash proposal consisting of upfront consideration of $1.10 per share, with CVR payments bringing the total potential consideration to $1.46 per share.

Also on April 6, 2023, Assertio submitted an updated proposal consisting of upfront consideration of $1.15 per share in Assertio common stock, with CVR payments (payable in stock or cash at Assertio’s election) bringing the total potential consideration to $1.30 per share. As part of this proposal, Assertio requested exclusivity through April 17, 2023, but Spectrum did not agree to such request, wishing to continue to negotiate with each of Assertio and Party B.

Later on April 6, 2023, the Spectrum board of directors held a virtual meeting to discuss updates in respect of the sale process and at which certain representatives of Spectrum senior management, Guggenheim Securities and Gibson Dunn were present for all or a portion of such meeting. Members of Spectrum’s

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senior management presented updates with respect to engagement with Party B and Assertio and discussed their view regarding Spectrum’s due diligence of Assertio, and their perspective on Assertio’s financial projections as a stand-alone company. A representative of Guggenheim Securities reviewed bidder engagement since the prior board meetings. Such representative reviewed each of Party B’s and Assertio’s revised proposals, as well as the requisite financing considerations for each party. Guggenheim Securities discussed certain precedent transactions comparable to the proposed transaction with each of Party B and Assertio and the likelihood of being able to achieve a signing and closing of the transaction on the proposed timeline with respect to each bidder. The Spectrum board of directors believed the Spectrum stockholders may prefer an all-cash transaction, subject to receipt of acceptable terms from Party B, though it expressed concern that there was significant execution risk in engaging with Party B in light of its lack of experience consummating strategic transactions, which was demonstrated by certain of their due diligence requests and engagement to date. Acknowledging its view that a strategic transaction was a better outcome for its stockholders than pursuing a standalone strategy, the Spectrum board of directors authorized Spectrum senior management and Guggenheim Securities to seek to finalize a proposal with either of Party B or Assertio at the highest price reasonably obtainable.

Between April 6, 2023 and April 12, 2023, Spectrum senior management and its advisors negotiated and engaged with Party B and its advisors to seek to finalize the transaction documents and respond to all of Party B’s diligence requests on the basis of its April 6, 2023 all-cash proposal of $1.10 per share in upfront consideration and CVR payments bringing the total potential consideration to $1.46 per share.

On April 7, 2023, following the discussion of the Spectrum board of directors, Spectrum management indicated to Assertio that it needed to increase the first CVR milestone payment amount so that the resulting total potential value of its offer would match Assertio’s March 31, 2023 proposal consisting of upfront consideration of $1.10 per share in Assertio common stock and two potential CVR milestone payments (payable in stock or cash at Assertio’s election) with an aggregate potential value equal to $0.25 per CVR. Spectrum management further indicated to Assertio that it was in discussions with Hanmi regarding its support of the proposed transaction.

Later on April 7, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives from Latham, SVB Securities and Wainwright. Assertio’s senior management team and Latham provided an update on the status of negotiations with Spectrum’s management team since the Assertio board of directors’ previous meeting and an overview of the remaining open items in the Merger Agreement, including certain closing conditions, regulatory covenants and a revised termination fee of a 3.75% to be included in an updated draft of the Merger Agreement to Spectrum. Assertio’s senior management team provided the Assertio board of directors with an update regarding ongoing discussions between Spectrum and Hanmi regarding a potential voting agreement in support of the proposed transaction. Representatives from SVB Securities reviewed the Assertio Projections with the Assertio board of directors that were proposed to be used in the preparation of each advisor’s fairness opinion. The Assertio board of directors approved the use of the Assertio Projections in preparing the fairness opinions. Later on April 7, 2023, Assertio submitted a further updated proposal (the “April 7 Proposal”) consisting of upfront consideration of $1.15 per share of Assertio common stock, with a CVR milestone payment (payable in stock or cash at Assertio’s election) of up to $0.10 per CVR in the event net revenue of ROLVEDON during calendar year 2024 exceeds $175 million and (ii) a CVR milestone payment (payable in stock or cash at Assertio’s election) of up to $0.10 per CVR in the event net revenue of ROLVEDON during calendar year 2025 exceeds $225 million, less any amount paid in connection with the 2024 milestone payment and, in each case, subject to a cap in the event that the CVR payments could result in the value of the upfront consideration constituting less than 80% of the aggregate merger consideration (the “CVR Cap”), bringing the total potential consideration to $1.35 per share. As part of this proposal, Assertio requested exclusivity through April 17, 2023, which Spectrum refused to grant.

Also on April 7, 2023, Latham, on behalf of Assertio, delivered an updated draft of the Merger Agreement and CVR Agreement for the proposed transaction to Gibson Dunn. Among other things, the Merger Agreement was updated to revise (i) proposed treatment of Spectrum equity awards, (ii) interim operating covenants applicable to Assertio and (iii) the termination fee equal to 3.75% of the total merger consideration. The CVR Agreement was revised to contemplate (i) payment of up to $0.10 per CVR (payable in stock or cash at Assertio’s election) upon achieving certain revenue milestones, consistent with

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the April 7 Proposal, (ii) revisions such that the milestone payments would only be measured based on net sales of ROLVEDON, and would not include Combination Products and (iii) revisions to the defined level of efforts standard proposed in Gibson Dunn’s April 4, 2023 draft of the CVR Agreement.

During early- to mid-April, Spectrum provided Hanmi with updates concerning Spectrum’s ongoing sale process. Around such time, Hanmi indicated its desire to renegotiate the drug substance fixed pricing under the Supply Agreement in connection with any proposed transaction with Assertio. Spectrum reminded Hanmi that pricing under the Supply Agreement was fixed through the latter half of 2025 and that Hanmi did not have the ability to renegotiate pricing terms in connection with the transaction, which Hanmi did not dispute. Hanmi informed Spectrum that it intended to abstain from any vote in a strategic transaction with Assertio due to Hanmi’s limited knowledge of Assertio and its strategy. On April 11, 2023, Spectrum conveyed to Assertio that Hanmi had indicated its desire to renegotiate pricing under the Supply Agreement in connection with the transaction.

On April 11, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present. Mr. Peisert provided an update regarding Spectrum’s continued discussions with Hanmi, including Hanmi’s request to renegotiate the fixed pricing under the Supply Agreement. Following discussions, the Assertio board of directors instructed Assertio’s management to pause continued negotiations with Spectrum regarding the proposed transaction until Spectrum had come to a resolution with Hanmi or modified its offer to address any potential future change in pricing under the Supply Agreement. Assertio indicated the same to Spectrum.

On April 12, 2023, the CEO of Party B, Party B’s counsel, Mr. Riga and Spectrum’s counsel held a meeting at which the CEO of Party B confirmed that its board of directors was supportive of the all-cash proposal of $1.10 per share in upfront consideration with CVR payments bringing the total potential consideration to $1.46 per share and that all documents were in agreed form among the parties. In addition, the CEO of Party B indicated that Party B would be prepared to sign and announce a merger agreement on such terms the following day, after each party’s final board meetings.

On April 13, 2023, Party B reduced the upfront consideration of its proposal to $0.85 per share citing additional discussions with its board of directors, the transaction size relative to its financial capacity and the long-term uncertainty around the Long Acting Granulocyte Colony Stimulating Factor market in which ROLVEDON competes.

On April 13, 2023, the Spectrum board of directors held a virtual meeting at which Spectrum management, Guggenheim Securities and Gibson Dunn were present for all or a portion of such meeting. During the meeting the Spectrum board of directors instructed Spectrum management, Guggenheim Securities and Gibson Dunn to cease engaging with Party B and its advisors but to continue to engage with Assertio in an effort to secure an acceptable proposal.

On April 19, 2023, Peter Staple, Chairman of the Assertio board of directors, met with Mr. Ashton to discuss the progress of Spectrum’s discussions with Hanmi regarding pricing under the Supply Agreement. In particular, Mr. Ashton noted that Spectrum had reminded Hanmi that pricing under the Supply Agreement was fixed through the latter half of 2025 and that Hanmi did not have the ability to renegotiate pricing terms in connection with the transaction, and that Hanmi had not disputed this. Mr. Ashton further relayed to Mr. Staple that Hanmi would not provide a voting and support agreement prior to the announcement of the transaction.

On April 19, 2023, Gibson Dunn, on behalf of Spectrum, delivered to Latham a revised draft of the Merger Agreement for the proposed transaction, which draft contemplated, among other things, (i) removing the requirement that Spectrum obtain a voting and support agreement from Hanmi with respect to the proposed transaction with Assertio, (ii) additional interim operating covenants for Assertio and (iii) a revised termination fee equal to $5,000,000.

On April 21, 2023, Gibson Dunn, on behalf of Spectrum, delivered to Latham a revised draft of the form of CVR Agreement, which draft contemplated, among other things, (i) net revenue generated in any twelve month period prior to the applicable milestone date would count towards meeting the applicable milestone, (ii) CVR payments would not be subject to the CVR Cap and (iii) revisions such that the milestone payments would be measured based on net sales of ROLVEDON, including Combination Products.

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Later on April 21, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives from Latham, SVB Securities, Wainwright and certain other advisors. Mr. Peisert then discussed with the board Hanmi’s prior request to renegotiate pricing under the Supply Agreement. Mr. Peisert and Mr. Staple understood from conversations with Spectrum that Spectrum had reminded Hanmi that pricing under the Supply Agreement was fixed through the latter half of 2025, and Hanmi had not disputed this. Mr. Peisert also informed the Board that Hanmi and Spectrum had previously engaged in discussions regarding the possibility of Hanmi acquiring Spectrum. Latham provided the Assertio board of directors with an overview of the Supply Agreement and other agreements between Spectrum and Hanmi, including certain key terms and how each agreement will be treated upon the closing of the proposed transaction. Assertio’s senior management provided Assertio’s board of directors with a preliminary feasibility assessment for a potential technology transfer of ROLVEDON drug substance manufacturing to a second supplier. Representatives from SVB Securities provided the Assertio board of directors with an update regarding the Assertio Projections and the Assertio adjusted Spectrum Projections that were proposed to be used in the preparation of each advisor’s fairness opinion. Following such discussions, the Assertio board of directors determined to rely on the existing contractual commitments under the Supply Agreement with Hanmi, and that (i) a $0.05 reduction in the per share purchase price, and (ii) subjecting the milestones for each CVR payment to dollar-for-dollar adjustment for any actual expenditure on technology transfer activity of ROLVEDON drug substance manufacturing to a second supplier, were appropriate to account for concerns discussed with respect to the Hanmi agreements and certain pricing considerations in SVB Securities’ presentation. The Assertio board of directors further determined that, given the execution risk implied by Hanmi’s participation in the process, Assertio should continue to require a termination fee at the high end of the market range in connection with the proposed transaction.

On April 22, 2023, Assertio submitted a revised proposal consisting of upfront consideration of $1.10 per share made up entirely of Assertio stock, with CVR payments (payable in stock or cash at Assertio’s election) bringing the total potential consideration to $1.30 per share.

On April 23, 2023, Latham, on behalf of Assertio, delivered to Gibson Dunn a revised draft of the Merger Agreement for the proposed transaction, which among other things, (i) revised certain interim operating covenants applicable to Assertio and Spectrum, (ii) clarified that Spectrum would have the right to designate one director to the Assertio board, subject to Assertio’s consent and (iii) included a termination fee equal to $9,187,500.

On April 23, 2023, Latham, on behalf of Assertio, additionally delivered an updated draft of the form of CVR Agreement to Gibson Dunn, which draft contemplated that (i) only net revenue generated during the 2024 and 2025 calendar years would count towards meeting the applicable milestone, (ii) CVR payments be subject to the CVR Cap and (iii) as a result of Hanmi’s indication to Spectrum that it would not sign a voting agreement in support of the transaction and the possibility that Hanmi may attempt to negotiate an increase of the pricing terms of the Supply Agreement when pricing comes up for negotiation in the latter half of 2025, milestones for each CVR payment would be subject to dollar-for-dollar adjustment for any actual expenditure on technology transfer activity in the event that Assertio determined, in its sole discretion, to pursue a technology transfer of ROLVEDON drug substance manufacturing to a second supplier.

On April 23, 2023, based on the last closing price of Spectrum’s shares and Assertio’s shares, Assertio and Spectrum agreed to convert Assertio’s proposal to an exchange ratio of 0.1783, which represented the $1.10 per share upfront consideration set forth in Assertio’s April 22 proposal. As of the close of business on April 24, 2023, the exchange ratio of 0.1783 represented upfront consideration of $1.14 per share, with CVR payments bringing the total potential consideration to $1.34 per share.

During the night of April 23, 2023, and throughout the course of April 24, 2023, Gibson Dunn and Latham exchanged several drafts of the Merger Agreement for the proposed transaction and the form of CVR Agreement and representatives of Gibson Dunn and Latham met virtually several times to discuss and finalize all terms the Merger Agreement and form of CVR Agreement. The parties agreed to a termination fee of $8.3 million (along with an expense reimbursement provision under certain circumstances described in greater detail in “The Merger Agreement — Termination Fees”) and to the inclusion of Combination Products for purposes of measuring the net sales milestones under the CVR Agreement.

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On April 24, 2023, the Assertio board of directors held a virtual meeting, with Assertio’s senior management team present along with representatives from Latham, SVB Securities, Wainwright and certain other advisors. A representative from Latham provided an update to the Assertio board of directors regarding the proposed final terms of the Merger Agreement and the CVR Agreement, along with an overview of the Board’s fiduciary duties under Delaware law both in general and in the context of the proposed transaction. Also at this meeting, after referencing its financial analyses of the Merger Consideration, SVB Securities delivered to the Assertio board of directors its oral opinion, which was subsequently confirmed by delivery of a written opinion dated April 24, 2023, to the effect that, as of such date and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered in connection with the preparation of such opinion, the Merger Consideration to be paid by Assertio pursuant to the terms of the Merger Agreement was fair, from a financial point of view, to Assertio, as more fully described under “Opinion of Assertio’s Financial Advisors — Opinion of SVB Securities LLC”. Also at this meeting, after referencing its financial analyses of the Merger Consideration, Wainwright delivered to the Assertio board of directors its oral opinion, subsequently confirmed by delivery of a written opinion dated April 24, 2023, to the effect that, as of such date and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered in connection with the preparation of such opinion, the Merger Consideration to be paid pursuant to the Merger Agreement was fair from a financial point of view to Assertio, as more fully described under “Opinion of Assertio’s Financial Advisors — Opinion of H.C. Wainwright & Co., LLC”. After discussions, including as to the matters described below under “Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger,” the Assertio board of directors unanimously (i) determined that the terms of the Merger Agreement and the merger were fair to and in the best interests of Assertio and its stockholders; (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the merger and the share issuance, each on the terms and subject to the conditions set forth in the Merger Agreement; and (iii) recommended that Assertio stockholders approve the Assertio Share Issuance Proposal.

In the evening on April 24, 2023, the Spectrum board of directors held a special virtual meeting at which certain representatives of Spectrum senior management, Guggenheim Securities and Gibson Dunn were present for all or a portion of such meeting. Representatives of Spectrum senior management provided the Spectrum board of directors an update with respect to the negotiation of the Merger Agreement and the form of CVR Agreement since the prior Spectrum board of directors meeting on April 6, 2023. Representatives of Guggenheim Securities then reviewed and discussed with the Spectrum board of directors its financial analyses with respect to the potential strategic transaction in light of the most recent trading prices of Spectrum shares and Assertio shares. Guggenheim Securities then delivered its oral opinion to the Spectrum board of directors, which opinion was subsequently confirmed in a written opinion dated April 24, 2023, to the effect that, as of such date, and based on and subject to the matters considered, the procedures followed, the assumptions made and various limitations of and qualifications to the review undertaken, the Exchange Ratio and CVR Consideration was fair, from a financial point of view, to the stockholders of Spectrum, as more fully described under “Opinion of Spectrum’s Financial Advisor — Opinion of Guggenheim Securities, LLC”. Thereafter, the Spectrum board of directors (other than Ms. Lim who had recused herself) unanimously (i) determined that the Merger Agreement, the merger and the other transactions contemplated by the Merger Agreement and the form of CVR Agreement were advisable and fair to, and in the best interests of, Spectrum and the Spectrum stockholders; (ii) approved, authorized, adopted and declared advisable the Merger Agreement, the merger and the other transactions contemplated by the Merger Agreement and the form of CVR Agreement; and (iii) recommended that the Spectrum stockholders vote in favor of adopting the Merger Agreement. For a description of the various factors considered by the Spectrum board of directors, see the section entitled “The Merger — Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger” of this joint proxy statement/prospectus.

Later on April 24, 2023, following the approval of the Merger Agreement and the merger by the Assertio board of directors and the Spectrum board of directors, Assertio and Spectrum finalized and executed the Merger Agreement, and on the morning of April 25, 2023, prior to the opening of trading, issued a joint press release announcing the transaction.

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Recommendation of the Assertio Board of Directors; Assertio’s Reasons for the Merger

At a special meeting held on April 24, 2023, the Assertio board of directors unanimously: (i) determined that the terms of the Merger Agreement and the Merger are fair to and in the best interests of Assertio and its stockholders; (ii) approved and declared advisable the Merger Agreement and the transactions contemplated thereby, including the Merger and the share issuance, each on the terms and subject to the conditions set forth in the Merger Agreement; and (iii) recommended that Assertio stockholders approve the Assertio share issuance proposal.

ACCORDINGLY, THE ASSERTIO BOARD OF DIRECTORS UNANIMOUSLY RECOMMENDS THAT ASSERTIO STOCKHOLDERS VOTE “FOR” THE ASSERTIO SHARE ISSUANCE PROPOSAL AND “FOR” THE ASSERTIO ADJOURNMENT PROPOSAL.

As described under “— Background of the Merger,” in evaluating the Merger Agreement and the transactions contemplated thereby, including the Merger and the share issuance, the Assertio board of directors held a number of meetings and consulted with Assertio senior management and its outside legal and financial advisors. In reaching its decision to approve the Merger Agreement and to recommend that Assertio stockholders vote to approve the Assertio share issuance proposal, the Assertio board of directors considered a number of factors, including, but not limited to the following (which are not necessarily presented in order of their relative importance to the Assertio board of directors):

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Benefits of the Acquisition. The Assertio board of directors believe that the acquisition of Spectrum enhances Assertio’s leadership position in the pharmaceutical industry and expands Assertio’s branded prescription portfolio. In particular, the Assertio board of directors noted:

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that the incorporation of ROLVEDON into Assertio’s product portfolio represents meaningful further asset and revenue diversification and extends the portfolio’s weighted average duration of exclusivity;

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the expectation that the Merger will be accretive to Assertio’s adjusted-EPS and operating cash flow beginning in 2024;

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that Assertio’s innovative digital non-personal sales model complements Spectrum’s in-person commercial infrastructure, providing greater market access and resources than either company as a standalone entity;

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the expectation that the combined company’s enhanced scale and greater diversification of revenue generating commercial assets is expected to result in a more attractive profile to investors and benefit from greater access to the capital markets;

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that the transaction enables the combined company to have a more scalable and competitive infrastructure for continuing the commercialization and acquisition of existing products suited to Assertio’s unique omni-channel sales strategy or Spectrum’s in-person oncology-focused commercial infrastructure;

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the Merger is expected to better position Assertio to benefit from specialty pharmaceutical market conditions, including opportunities for additional company and product acquisitions;

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the fact that, upon completion of the transactions, the five person board of directors of Assertio will be expanded to include an additional Spectrum director nominee; and

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the Assertio board of directors’ consideration of the structure of the transaction as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code as discussed under “— U.S. Federal Income Tax Considerations Relating to the Merger”.

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Exchange Ratio and Merger Consideration. The Assertio board of directors considered the relative favorability of the exchange ratio relative to the exchange ratios historically implied by the relative trading prices of Assertio and Spectrum common stock over various periods and relative to the current assessment of the valuation of each company and of the synergies and other benefits of the Merger, in addition to:

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the fact that, upon completion of the Merger (without consideration of the shares of Assertio common stock underlying the CVRs), Assertio stockholders and former Spectrum stockholders

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will own approximately 65% and 35%, respectively, of the combined company (based on fully diluted shares outstanding of the combined company);

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the fact that the CVRs will require Assertio to pay additional consideration only upon achievement of certain net sales milestones with respect to ROLVEDON, and on other terms and conditions specified in the CVR Agreement;

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the oral opinion of SVB Securities, rendered to the Assertio board of directors, subsequently confirmed in a written opinion dated April 24, 2023, to the effect that, as of April 24, 2023, and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by SVB Securities in connection with the preparation of its opinion, the Merger Consideration provided for in the Merger Agreement was fair, from a financial point of view, to Assertio (which opinion is more fully described below under “— Opinions of Assertio’s Financial Advisors — Opinion of SVB Securities LLC” and is attached as Annex C hereto); and

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the oral opinion of Wainwright, rendered to the Assertio board of directors, subsequently confirmed in a written opinion dated April 24, 2023, to the effect that, as of April 24, 2023, and subject to the procedures followed, assumptions made, qualifications and limitations on the review undertaken and other matters considered by Wainwright in connection with the preparation of its opinion, the consideration to be paid pursuant to the Merger Agreement, consisting of the Merger Consideration, was fair from a financial point of view to Assertio (which opinion is more fully described below under “— Opinions of Assertio’s Financial Advisors — Opinion of H.C. Wainwright & Co., LLC” and is attached as Annex D hereto).

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Other Factors Considered by the Assertio Board of Directors. In addition to considering the factors described above, the Assertio board of directors considered the following additional factors that weighed in favor of the Merger:

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historical information concerning Assertio’s and Spectrum’s respective businesses, financial condition, results of operations, earnings, trading prices, managements, competitive positions and prospects on stand-alone and forecasted combined bases; and

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the current and prospective business environment in which Assertio and Spectrum operate, including international, national and local economic conditions and the competitive and regulatory environment, and the likely effect of these factors on Assertio and the combined company.

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Terms of the Merger Agreement. The Assertio board of directors considered that the terms of the Merger Agreement, taken as a whole, including the parties’ representations, warranties and covenants, and the circumstances under which the Merger Agreement may be terminated, in its belief, are reasonable. The Assertio board of directors also reviewed and considered the conditions to the completion of the Merger, and concluded that while the completion of the Merger is subject to customary closing conditions, such conditions were likely to be satisfied on a timely basis.

The Assertio board of directors weighed these advantages and opportunities against a number of potentially negative factors in its deliberations concerning the Merger Agreement and the Merger, including:

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the risk that Spectrum’s financial performance may not meet Assertio’s expectations;

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the risk that, because the exchange ratio under the Merger Agreement would not be adjusted for changes in the market price of Assertio or Spectrum common stock, the then-current trading price of the shares of Assertio common stock to be issued to holders of shares of Spectrum common stock upon the consummation of the Merger could be significantly higher than the trading price prevailing at the time the Merger Agreement was entered into;

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the fact that each of the opinions of SVB Securities and Wainwright as to the fairness, from a financial point of view, of the Merger Consideration set forth in the Merger Agreement speaks only as of the date of such opinion and did not and will not take into account events occurring or information that becomes available after such date, including any changes in the operations and prospects of Assertio or Spectrum, general economic, monetary, market and other conditions and

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other factors that may be beyond the control of Assertio and Spectrum and on which the fairness opinions were based, any of which may be material;

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the risks inherent in the businesses of Assertio and Spectrum, including the costs and risks of manufacturing and supply issues and delay and failure in clinical development programs and commercial launch efforts;

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the risks posed by certain pending securities litigation (and related derivative actions) that Spectrum is subject to with respect to its ROLVEDON and poziotinib products, as described in greater detail in Spectrum’s public filings;

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the risk that the Merger may not be completed or may be delayed despite the parties’ efforts, including the possibility that conditions to the parties’ obligations to complete the Merger may not be satisfied, and the potential resulting disruptions to Assertio’s and Spectrum’s businesses;

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the potential length of the regulatory approval process and the possibility that governmental authorities might seek to require certain actions of Assertio or Spectrum or impose certain terms, conditions or limitations on Assertio’s or Spectrum’s businesses in connection with granting approval of the Merger or might otherwise seek to prevent or delay the Merger;

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the difficulties and challenges inherent in completing the Merger and integrating the businesses, operations and workforce of Spectrum with those of Assertio and the possibility of encountering difficulties in achieving expected revenue growth;

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the possible diversion of management attention for an extended period of time during the pendency of the Merger and, following closing, the integration of the two companies;

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the substantial costs to be incurred in connection with the Merger, including those incurred regardless of whether the Merger is consummated;

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the risk that Assertio stockholders may not approve the Assertio share issuance proposal at the Assertio special meeting or that Spectrum stockholders may not approve the adoption of the Merger Agreement at the Spectrum special meeting;

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that Assertio would be required to pay to Spectrum a termination fee of $8.3 million in the event the Merger Agreement were to be terminated by Assertio in order to accept a superior acquisition proposal from another bidder or a change in the recommendation by the Assertio board of directors to its stockholders with respect to approval of the share issuance (as more fully described below under “— The Merger Agreement — Assertio Termination Fee”);

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the ability of the Spectrum board of directors, subject to certain conditions, to change its recommendation supporting the Merger in response to a superior proposal or an intervening event other than a superior proposal, if the Spectrum board of directors determines in good faith, after consultation with its outside legal counsel and its financial advisor, that failure to take such action would reasonably be expected to be inconsistent with the Spectrum board of directors’ fiduciary duties to its stockholders under applicable laws;

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the ability of the Spectrum board of directors, subject to certain conditions, to terminate the Merger Agreement in order to enter into a definitive agreement providing for a superior proposal; and

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risks of the type and nature described under entitled “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements.”

The Assertio board of directors considered all of these factors as a whole and, on balance, concluded that the potential benefits of the Merger outweighed the risks and uncertainties of the Merger.

In addition, the Assertio board of directors was aware of and considered that Assertio directors and executive officers would have the right to continued service for, employment by and the right to continued indemnification by the combined company. See “Interests of Assertio’s Directors and Executive Officers in the Merger.”

The foregoing discussion of the information and factors that the Assertio board of directors considered is not intended to be exhaustive, but rather is meant to include the material factors that the Assertio board

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of directors considered. The Assertio board of directors collectively reached the conclusion to approve the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement in light of the various factors described above and other factors that the members of the Assertio board of directors believed were appropriate. In view of the complexity and wide variety of factors, both positive and negative, that the Assertio board of directors considered in connection with its evaluation of the Merger, the Assertio board of directors did not find it practical, and did not attempt, to quantify, rank or otherwise assign relative or specific weights or values to any of the factors it considered in reaching its decision and did not undertake to make any specific determination as to whether any particular factor, or any aspect of any particular factor, was favorable or unfavorable to the ultimate determination of the Assertio board of directors. In considering the factors discussed above, individual directors may have given different weights to different factors.

The foregoing description of Assertio’s consideration of the factors supporting the Merger is forward-looking in nature. This information should be read in light of the factors discussed under “Cautionary Statement Regarding Forward-Looking Statements.”

Recommendation of the Spectrum Board of Directors; Spectrum’s Reasons for the Merger

The Spectrum board of directors, at a meeting held on April 24, 2023, among other things, (i) determined that the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement are fair and in the best interest of, and are advisable to, Spectrum and the Spectrum stockholders, (ii) approved and adopted the Merger Agreement and approved the Merger and the other transactions contemplated by the Merger Agreement and (iii) recommended that the Spectrum stockholders approve the Merger Agreement. The Spectrum board of directors recommends that Spectrum stockholders vote “FOR” the Spectrum merger proposal.

As described above in the section titled “The Merger — Background of the Merger” beginning on page 71 of this joint proxy statement/prospectus, in evaluating the Merger Agreement, the Merger and the other transactions contemplated by the Merger Agreement, the Spectrum board of directors consulted with Spectrum’s senior management, outside legal counsel and Spectrum’s financial, tax and strategy advisors. The Spectrum board of directors determined that entering into the Merger Agreement with Assertio was fair and in the best interests of, and advisable to, Spectrum and Spectrum stockholders. In arriving at this determination and in recommending that the Spectrum stockholders vote their shares of Spectrum common stock in favor of adoption of the Merger Agreement, the Spectrum board of directors considered a number of factors, including the following factors (not necessarily in order of relative importance) which the Spectrum board of directors viewed as being generally positive or favorable in coming to its determination, approval and related recommendation:

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The Spectrum board of directors’ belief that the Merger will create a differentiated pharmaceutical company with complementary businesses, which will enhance opportunities for product cross-selling and market expansion and benefit stockholders by creating long-term growth potential.

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The Spectrum board of directors’ belief that the Merger will allow for Spectrum to commercialize ROLVEDON faster and more efficiently than Spectrum could achieve on a standalone basis.

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The Spectrum board of directors’ belief that the combined company is more valuable to Spectrum’s stockholders than Spectrum’s value as an independent, standalone public company. The Spectrum board of directors reviewed Spectrum’s business, operations, assets, operating results, financial conditions, prospects, business strategy, competitive position and industry, including the potential impact (which cannot be quantified numerically) of those factors on the trading price of Spectrum’s common stock, to assess the prospects and risks associated with remaining an independent, standalone public company, including:

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the risks associated with the marketing and commercialization of ROLVEDON and the early-stage nature of Spectrum’s other product candidates which may not be successfully developed into products that are marketed and sold, and the development of Spectrum’s product pipeline, including the initiation and completion of planned preclinical studies and clinical trials, delays or failures to obtain or make applicable regulatory filings and approvals, the

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uncertainty of FDA approval for Spectrum’s product candidates and the risk that Spectrum’s ongoing product development activities are not successful;

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the cost that Spectrum would be required to incur to commercialize ROLVEDON and its other product candidates on a standalone basis, if its preclinical studies and clinical trials are successful and FDA approval is received;

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the capital requirements forecasted to achieve profitability, the uncertainty of availability of adequate capital to Spectrum on reasonable terms for Spectrum to effectively launch its product candidates, if approved, independently, and the significant dilution to existing stockholders that would likely result from future fundraising at Spectrum;

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the uncertainty regarding future pricing for Spectrum’s product candidates for the indications currently being considered and uncertainty regarding the availability of, level of, or restrictions related to reimbursement from insurance companies and government payors;

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potential future competition, including from larger and better funded companies which might have competitive advantages from their broader commercial scope and economies of scale in pricing;

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the risks inherent in the pharmaceutical industry and, in light of the regulatory, financial and competitive challenges facing industry participants, the belief of the Spectrum board of directors that the combined company following the Merger would be better positioned to meet these challenges if the expected strategic and financial benefits of the transaction were fully realized; and

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the risks of failure of Spectrum’s ongoing preclinical studies or any clinical trials.

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The expectation that, following the Merger, the combined company would have a strong financial and credit profile, which may unlock access to capital that is not available to Spectrum on a standalone basis.

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The Spectrum board of directors’ consideration, with the assistance of Spectrum’s advisors and Spectrum senior management, of the potential for alternative transactions or remaining as a standalone company, and belief that it was unlikely that an alternative transaction or remaining as a standalone company would provide more long-term value to the Spectrum stockholders than the Merger.

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The Spectrum board of directors’ belief that the combined company’s enhanced scale and diversified revenue mix would result in improved opportunities for growth and cost savings and enhance the combined company’s ability to capitalize on new growth opportunities and to compete for customers and key employee talent.

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The Spectrum board of directors’ belief that the combined company will have enhanced scale and sufficient balance sheet flexibility to make technological and other investments to serve customers.

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The implied value of the Upfront Merger Consideration to be received by Spectrum stockholders (which was $1.14 per share of Spectrum common stock, calculated based on the closing price of Assertio common stock on the Nasdaq on April 24, 2023, representing a premium of approximately 65% over the closing price of the Spectrum common stock on the same date and a premium of approximately 61.4% over the 30-day volume weighted average trading price of the Spectrum common stock).

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The fact that the exchange ratio in the Merger is fixed and will not fluctuate as a result of changes in the market value of Assertio common stock or Spectrum common stock, which provides certainty as to the respective pro forma percentage ownership of the combined company, limits the impact of external factors on the Merger and affords Spectrum stockholders the opportunity to benefit from any increase in the market value of the Assertio common stock between the announcement and consummation of the Merger.

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The fact that the consideration to be received by Spectrum stockholders in the Merger, consisting of shares of Assertio common stock, which will be listed for trading on the Nasdaq, continues to provide liquidity for Spectrum stockholders desiring to liquidate their investment after the Merger

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and provides Spectrum stockholders the opportunity to participate in the future growth of the combined company following the Merger.

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The fact that the Merger Consideration includes one CVR per share, which provides Spectrum stockholders an opportunity to realize additional value from future payments.

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The fact that the strategic combination with Assertio will allow the Spectrum stockholders to have a meaningful ownership interest in the combined company, with an expected pro forma ownership of approximately 35%, and allow certain continuing Spectrum officers and directors to participate in the execution of the strategy and business plan of the combined company through the appointment of one Spectrum director to the Assertio board of directors, in each case effective as of the closing.

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The requirement that Spectrum stockholders approve the Spectrum merger proposal as a condition to the Merger.

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The Spectrum board of directors’ consideration of the fact that Guggenheim Securities engaged in discussions with over 40 potential counterparties, which the Spectrum board of directors, Spectrum management and Guggenheim Securities believed could be likely interested parties, concerning their interest in an acquisition of Spectrum, and that no other counterparty provided a better offer.

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The Spectrum board of directors considered the oral opinion, which was confirmed by delivery of a written opinion each dated as of April 24, 2023, of Guggenheim Securities, as to the fairness, from a financial point of view and as of the date of the opinion, of the exchange ratio and CVR consideration (taken together), to the stockholders of Spectrum, which opinion was based on and subject to the matters considered, the procedures followed, the assumptions made and various limitations of and qualifications to the review undertaken as more fully described under the section entitled “The Merger — Opinion of Spectrum’s Financial Advisor — Opinion of Guggenheim Securities, LLC” beginning on page 105 of this joint proxy statement/prospectus.

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The Spectrum board of directors’ and Spectrum senior management’s knowledge of the business, product portfolio, operations, financial condition, earnings and prospects of Assertio and Spectrum, taking into account the results of Spectrum’s due diligence review of Assertio, the expected pro forma effect of the Merger on the combined company, as well as its and their knowledge of the current and prospective environment in which Assertio and Spectrum operate, including economic and market conditions.

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The Spectrum board of directors’ consideration of the terms of the Merger Agreement related to Spectrum’s ability to respond to unsolicited acquisition proposals and determination that third parties would be unlikely to be deterred from making a competing proposal by the provisions of the Merger Agreement, including because the Spectrum board of directors may, under certain circumstances, furnish information with respect to Spectrum and participate in discussions or negotiations in connection with an acquisition proposal if necessary to comply with their fiduciary duties, including that:

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subject to its compliance with the Merger Agreement and prior to the adoption of the Merger Agreement by the Spectrum stockholders, the Spectrum board of directors can change its recommendation to the Spectrum stockholders with respect to the adoption of the Merger Agreement if, among other things, it determines that the failure to withdraw or modify its recommendation to the Spectrum stockholders would be reasonably likely to be inconsistent with its fiduciary duties under applicable law; and

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while the Merger Agreement contains the Company Termination Fee that Spectrum would be required to pay to Assertio in certain circumstances, the Spectrum board of directors believes that the Company Termination Fee is reasonable in light of such circumstances and the overall terms of the Merger Agreement, consistent with fees in comparable transactions, and not preclusive of other offers. For further discussion regarding the circumstances in which Spectrum would be required to pay the Company Termination Fee to Assertio, please see the section titled “The Merger Agreement — Termination Fees — Spectrum Termination Fee” beginning on page 149 of this joint proxy statement/prospectus.

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The fact that upon termination of the Merger Agreement in certain circumstances, Assertio would be required to pay to Spectrum the Parent Termination Fee, as applicable, that would help offset some of the costs of the transaction as further described in the section titled “The Merger Agreement — Termination Fees — Assertio Termination Fee” beginning on page 150 of this joint proxy statement/prospectus.

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The fact that if the Merger Agreement is terminated by either party because Assertio shareholders do not approve the Merger, then Assertio has agreed to reimburse Spectrum for the Company Expenses, as further described in the sections titled “The Merger Agreement — Termination Fees — Spectrum Termination Fee” and “The Merger Agreement — Termination Fees — Assertio Termination Fee” beginning on pages 148 and 149 of this joint proxy statement/prospectus, respectively.

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The Spectrum board of directors’ belief in the ability of Assertio senior management to successfully oversee the integration of and operations of Spectrum’s business.

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The Spectrum board of directors’ belief that the combined company will offer opportunities for career advancement to Spectrum and Assertio personnel within the combined company.

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The fact that Spectrum and Assertio agreed to use their respective reasonable best efforts to consummate the Merger and obtain the necessary approvals and clearances required under applicable Antitrust Laws.

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The Spectrum board of directors’ belief that, although the consummation of the Merger is subject to approval under the HSR Act, such approval is likely to be obtained and the Merger consummated on a timely basis.

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The Spectrum board of directors’ belief of the reasonable likelihood that the Merger will be consummated based on, among other things, the conditions to the Merger and that the Termination Date allows for sufficient time to consummate the Merger.

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The Spectrum board of directors’ belief that the strong track record of Assertio’s senior management team as an experienced acquirer and proven integrator will facilitate an effective and timely integration of the two companies’ operations.

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The fact that there are no financing conditions or contingencies, and that Assertio does not require financing in order to consummate the Merger.

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The fact that Spectrum has the right to specifically enforce Assertio’s obligations under the Merger Agreement.

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The fact that the Merger is intended to qualify for the Intended Tax Treatment for U.S. federal income tax purposes with the result that holders of shares of Spectrum common stock that are subject to U.S. federal income taxation generally will not recognize any gain or loss for U.S. federal income tax purposes upon the receipt of Assertio common stock in exchange for Spectrum common stock in the Merger.

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The Spectrum board of directors’ belief, based on its review in consultation with Spectrum advisors, that the structure of the Merger and the financial and other terms of the Merger Agreement, taken as a whole, including the parties’ representations, warranties and covenants and the circumstances under which the Merger Agreement may be terminated, including related termination fees, are reasonable.

The Spectrum board of directors also considered and balanced against the potentially positive factors a number of uncertainties, risks and factors it deemed generally negative or unfavorable in making its determination, approval and related recommendation, including the following (not necessarily in order of relative importance):

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The fact that the Spectrum stockholders will not receive cash in the transaction even though certain of the Spectrum stockholders may desire liquidity.

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The fact that the CVRs may not be sold, assigned, transferred, pledged or encumbered, subject to limited exceptions, and will not be registered with the SEC or listed on any securities exchange.

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The fact that obligations in respect to the CVRs will represent general, unsecured obligations of Assertio and that holders of the CVRs will face the same risks with respect to the future financial capability of Assertio to satisfy its obligations under the CVRs as any general, unsecured creditor of Assertio.

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The fact that, after the Merger, Spectrum stockholders will have a significantly lower ownership and voting interest in the combined company than they currently have in Spectrum and will exercise less influence over management.

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The ability of Assertio to terminate the Merger Agreement (i) under specified circumstances in order to enter into an agreement providing for the implementation of an Assertio Superior Proposal upon payment by Assertio to Spectrum of the Parent Termination Fee, or (ii) under specified other circumstances, as applicable, upon payment by Assertio to Spectrum of the Company Expenses; for more information, see the sections titled “The Merger Agreement — Termination of the Merger Agreement” and “The Merger Agreement — Termination Fees — Assertio Termination Fee” beginning on pages 147 and 149 of this joint proxy statement/prospectus, respectively.

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The limitations on Spectrum’s ability to solicit alternative transactions prior to the termination of the Merger Agreement or consummation of the Merger.

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Spectrum’s obligation to pay to Assertio the Company Termination Fee or the Parent Expenses, as applicable, if the Merger Agreement is terminated under specified circumstances; for more information, see the section titled “The Merger Agreement — Termination Fees — Spectrum Termination Fee” beginning on page 148 of this joint proxy statement/prospectus.

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The possibility that the Company Termination Fee could potentially deter a potential acquirer from proposing an alternative transaction that would provide greater value to Spectrum stockholders than the proposed Merger.

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Notwithstanding the likelihood of the Merger being consummated, the Merger may not be consummated, or that consummation may be unduly delayed, including because Spectrum stockholders may not approve the Merger and the other transactions contemplated by the Merger Agreement, the Assertio stockholders may not approve the Share Issuance Proposal, applicable regulatory approvals may not be obtained or because of reasons beyond the control of Assertio and Spectrum.

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The possibility that governmental entities may oppose or refuse to grant regulatory clearances of the Merger or impose conditions on Assertio and Spectrum prior to approving the Merger that may adversely impact the ability of the combined company to realize the anticipated benefits that are projected to occur in connection with the Merger.

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The impact that failure to consummate or delays in consummating the Merger and the other transactions contemplated by the Merger Agreement could have on the market value of shares of Spectrum common stock and Spectrum’s operating results.

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The cost savings, cost synergies and other benefits to the Spectrum stockholders that are expected to result from the Merger might not be fully realized or not realized at all.

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The challenges of integrating the businesses, management teams, operations, workforce, strategies and organizations of Assertio and Spectrum, including the possibility that the Merger and resulting integration process could result in the disruption of ongoing business.

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The substantial costs to be incurred in connection with the transaction, including the transaction expenses arising from the Merger and the costs of integrating the businesses of Assertio and Spectrum.

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The fact that Spectrum’s directors and executive officers may have interests in the Merger that are different from, or in addition to, those of Spectrum’s stockholders generally, including that one of Spectrum’s directors will serve as a director on the Assertio board of directors following the Merger and certain interests arising from the employment and compensation arrangements of Spectrum’s executive officers and the manner in which they would be affected by the Merger, as detailed in the sections titled “Interests of Spectrum’s Directors and Executive Officers in the Merger” and “Interests of Spectrum’s Directors and Executive Officers in the Merger” beginning on pages 166 and 167 of this joint proxy statement/prospectus, respectively.

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The restrictions on the conduct of Spectrum’s business during the period between the execution of the Merger Agreement and the consummation of the Merger; for more information, see the section titled “The Merger Agreement — Conduct of Business Prior to the Merger’s Completion” beginning on page 136 of this joint proxy statement/prospectus.

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The diversion of management focus and resources from operational matters and other strategic opportunities while working to implement the Merger.

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The combined company’s potential inability to retain key employees.

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The fixed exchange ratio will not adjust to compensate for any increase in the market value of Spectrum common stock prior to the consummation of the Merger.

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The fact that the opinion of Guggenheim Securities as to the fairness to the stockholders of Spectrum, from a financial point of view, of the exchange ratio and CVR consideration speaks only as of the date of such opinion and did not and will not take into account events occurring or information that has become available after such date, including any changes in the operations and prospects of Spectrum or Assertio, financial, economic, market and other conditions and other factors that may be beyond the control of Spectrum and Assertio and on which such opinion was based, any of which may be material.

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Other matters described in the sections titled “Cautionary Statement Regarding Forward-Looking Statements” and “Risk Factors” beginning on pages 34 and 36 of this joint proxy statement/prospectus, respectively.

The Spectrum board of directors considered all of these factors as a whole, as well as others, and, on balance, concluded that the potential benefits of the Merger to Spectrum stockholders outweighed the risks, uncertainties, restrictions and potentially negative factors associated with the Merger.

The foregoing discussion of factors considered by the Spectrum board of directors is not, and is not intended to be, exhaustive. The Spectrum board of directors collectively reached the conclusion to approve the Merger Agreement in light of the various factors described above and other factors that the members of the Spectrum board of directors believed were appropriate. In light of the variety of factors considered in connection with its evaluation of the Merger, the Spectrum board of directors did not find it practicable to, and did not, quantify or otherwise assign relative weights to the specific factors considered in reaching its determinations and recommendations. Moreover, each member of the Spectrum board of directors applied his or her own personal business judgment to the process and may have given different weight to different factors. The Spectrum board of directors did not undertake to make any specific determination as to whether any factor, or any particular aspect of any factor, supported or did not support its ultimate determination. The Spectrum board of directors based its recommendation on the totality of the information available to it, including discussions with Spectrum’s management and outside legal and financial advisors.

It should be noted that this explanation of the reasoning of the Spectrum board of directors and certain information presented in this section is forward-looking in nature and should be read in light of the factors set forth in the section titled “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 34 of this joint proxy statement/prospectus.

Opinions of Assertio’s Financial Advisors

Opinion of SVB Securities LLC

Introduction

Assertio retained SVB Securities as its financial advisor in connection with the Merger and the other transactions contemplated by the Merger Agreement, which are referred to throughout this section, collectively, as the “Transaction.” In connection with this engagement, Assertio requested that SVB Securities evaluate the fairness, from a financial point of view, to Assertio of the Merger Consideration. On April 24, 2023, SVB Securities rendered to the Assertio board of directors its oral opinion, which was subsequently confirmed by delivery of a written opinion dated April 24, 2023 that, as of such date and based upon and

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subject to the various assumptions, qualifications and limitations upon the review undertaken by SVB Securities in preparing its opinion, the Merger Consideration provided for in the Merger Agreement was fair, from a financial point of view, to Assertio.

The full text of SVB Securities’ written opinion, dated April 24, 2023, which describes the assumptions made and limitations upon the review undertaken by SVB Securities in preparing its opinion, is attached as Annex C and is incorporated herein by reference. The summary of SVB Securities’ written opinion set forth below is qualified in its entirety by the full text of the written opinion attached as Annex C. SVB Securities’ financial advisory services and opinion were provided for the information and assistance of the Assertio board of directors (in their capacity as directors and not in any other capacity) in connection with and for purposes of its consideration of the Transaction and SVB Securities’ opinion addressed only the fairness, from a financial point of view, as of the date thereof, to Assertio of the Merger Consideration proposed to be paid by Assertio pursuant to the terms of the Merger Agreement. SVB Securities’ opinion did not address any other term or aspect of the Merger Agreement or the Transaction and does not constitute a recommendation to any stockholder of Assertio or Spectrum as to whether or how such holder should vote with respect to the Merger or otherwise act with respect to the Transaction or any other matter.

In connection with rendering the opinion described above and performing its related financial analyses, SVB Securities reviewed, among other things:

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a draft, dated April 24, 2023, of the Merger Agreement;

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a draft, dated April 24, 2023, of the CVR Agreement;

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the Annual Reports on Form 10-K for the fiscal year ended December 31, 2022, as filed by each of Assertio and Spectrum with the SEC;

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certain Current Reports on Form 8-K, as filed by each of Assertio and Spectrum with, or furnished by each of Assertio and Spectrum to, the SEC;

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certain publicly available research analyst reports for each of Assertio and Spectrum; and

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certain financial forecasts and other information and data, relating to each of Assertio and Spectrum prepared by management of Assertio and furnished to us by Assertio for purposes of SVB Securities’ analysis, which financial forecasts are described further under “The Merger — Assertio Unaudited Financial Projections” and “— Spectrum Unaudited Financial Projections” (the “Forecasts”).

SVB Securities also conducted discussions with members of the senior management and representatives of Assertio regarding their assessment of the Forecasts. In addition, SVB Securities reviewed the historical trading prices and trading activity for the Assertio common stock and the Spectrum common stock. Furthermore, SVB Securities reviewed publicly available financial and stock market data regarding companies in the biopharmaceutical industry that SVB Securities believed to be comparable in certain respects to each of Assertio and Spectrum. SVB Securities also conducted such other financial studies and analyses and took into account such other information as SVB Securities deemed appropriate.

SVB Securities assumed, without independent verification or any responsibility therefor, the accuracy and completeness of the financial, legal, regulatory, tax, accounting and other information supplied to, discussed with, or reviewed by SVB Securities for purposes of its opinion and, with the consent of the Assertio board of directors, relied upon such information as being complete and accurate. In that regard, SVB Securities assumed, with the consent of the Assertio board of directors, that the Forecasts had been reasonably prepared on bases reflecting the best currently available estimates and judgments of the management of Assertio as to the matters covered thereby. SVB Securities relied, at the direction of the Assertio board of directors, on the Forecasts for purposes of SVB Securities’ analysis and its opinion. SVB Securities expressed no view or opinion as to the Forecasts or the assumptions on which they were based. In addition, with the consent of the Assertio board of directors, SVB Securities did not make any independent evaluation or appraisal of any of the assets or liabilities (contingent, derivative, off-balance-sheet or otherwise) of Assertio or Spectrum, nor was SVB Securities furnished with any such evaluation or appraisal, and SVB Securities was not asked to conduct, and did not conduct, a physical inspection of the properties or

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assets of Assertio or Spectrum. Furthermore, at the direction of the Assertio board of directors, SVB Securities ascribed no value to the CVRs issuable pursuant to the CVR Agreement.

SVB Securities assumed, with the consent of the Assertio board of directors, that the final executed Merger Agreement and CVR Agreement would not differ in any respect material to SVB Securities’ analysis or its opinion from the last drafts of the Merger Agreement and CVR Agreement reviewed by SVB Securities. SVB Securities also assumed, with the consent of the Assertio board of directors, that the T