WHERE YOU CAN FIND ADDITIONAL INFORMATION

        This Joint Proxy Statement/Prospectus incorporates by reference important business and financial information about Assertio that is not included in or delivered with this Joint Proxy Statement/Prospectus, which is available without charge from the U.S. Securities and Exchange Commission's (the "SEC") website at www.sec.gov. See "Incorporation of Certain Information by Reference" on page 4. Copies of documents related to Assertio may also be obtained without charge from the Internet at www.assertiotx.com, under the "Investors" section, by contacting Assertio Therapeutics, Inc., 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045, Attn: Investor Relations, or by calling (224) 419-7106. If you wish to obtain any of these documents from Assertio you should make your request no later than May 12, 2020 to ensure timely delivery.

        Copies of documents related to Zyla, including Zyla's Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, ownership reports for insiders and any amendments to these reports filed with or furnished to the SEC are available free of charge on the SEC's website at www.sec.gov. These documents may also be obtained without charge under the "Investor Relations" section of Zyla's Internet website at www.zyla.com as soon as reasonably practicable after filing with the SEC, by contacting Zyla at Zyla Life Sciences, Attn: Secretary, 600 Lee Road, Suite 100, Wayne, PA 19087 or by calling (610) 833-4200.

        Assertio has appointed Innisfree M&A Incorporated as proxy solicitor for the Joint Proxy Statement/Prospectus solicitation. Any questions about the Merger, requests for additional copies of documents or assistance voting your shares may be directed to Innisfree M&A Incorporated by telephone toll-free at (877) 717-3930 (banks and brokers may call collect at (212) 750-5833.

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INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

        Assertio files annual, quarterly and current reports, proxy statements and other information with the SEC. Assertio's SEC filings are available to the public from commercial retrieval services and are available at the Internet website maintained by the SEC at www.sec.gov. The filings are also available on Assertio's website at http://www.assertiotx.com. The information contained in Assertio's website does not constitute a part of this Joint Proxy Statement/Prospectus.

        Assertio is "incorporating by reference" into this Joint Proxy Statement/Prospectus the information in certain documents that Assertio previously filed with the SEC, which means that Assertio can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this Joint Proxy Statement/Prospectus. Any reports filed by Assertio on or after the date of this Joint Proxy Statement/Prospectus supersede any information contained, or incorporated by reference, herein. Assertio incorporates by reference in this Joint Proxy Statement/Prospectus the documents listed below and any filings on or after the date hereof that Assertio makes with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), excluding any information furnished pursuant to Item 2.02 or Item 7.01 on any Current Report on Form 8-K. The future filings with the SEC made by Assertio will automatically update and supersede any inconsistent information in this Joint Proxy Statement/Prospectus and any earlier dated incorporated document.

•

Assertio's Annual Report on Form 10-K for the fiscal year ended December 31, 2019, filed on March 10, 2020; and



•

Assertio's Current Reports on Form 8-K filed on January 13, 2020, January 16, 2020, February 7, 2020, February 13, 2020, February 20, 2020, and March 17, 2020.

        This Joint Proxy Statement/Prospectus does not incorporate by reference any documents or portions thereof or exhibits thereto specifically listed above that are deemed furnished and not filed with the SEC.

        You may also request a copy of any or all of the documents referred to above that have been or will be incorporated by reference into this Joint Proxy Statement/Prospectus (other than an exhibit to a filing unless that exhibit is specifically incorporated by reference into that filing) at no cost, by writing to Assertio at 100 South Saunders Road, Suite 300, Lake Forest, Illinois, 60045, and Assertio's telephone number is (224) 419-7106.

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QUESTIONS AND ANSWERS ABOUT THE PROPOSALS AND STOCKHOLDER MEETINGS

General Questions and Answers for Assertio Stockholders and Zyla Stockholders

Q:

What are the proposed Transactions?

A:

Assertio, certain of Assertio Therapeutics' subsidiaries, and Zyla entered into the Merger Agreement, which is attached to this Joint Proxy Statement/Prospectus as Annex A. The Merger Agreement provides for a business combination of Assertio Therapeutics and Zyla by means of a two-step merger process. As a result of the transactions contemplated by the Merger Agreement, Assertio Therapeutics' and Zyla's respective businesses will be owned by a new holding company, which we refer to as "Assertio Holdings" or the "combined company." We sometimes refer to the Merger and the other transactions contemplated by the Merger Agreement, taken as a whole, as the "transactions."

In the first merger, a subsidiary of Assertio Holdings formed specifically for the purpose of effectuating the transactions will merge with and into Assertio Therapeutics. Assertio Therapeutics will be the surviving company in this merger and will become a wholly-owned subsidiary of Assertio Holdings. We refer to this first merger as the "Assertio Reorganization." Following consummation of the Assertio Reorganization, Assertio Therapeutics may be merged with and into a newly-formed Delaware limited liability company that is a direct wholly-owned subsidiary of Assertio Holdings with the limited liability company surviving (the "Assertio LLC Conversion").

In the second merger, which will occur simultaneously or promptly following the Assertio Reorganization, a second subsidiary of Assertio Holdings, also formed specifically for the purpose of effectuating the transactions, will merge with and into Zyla. Zyla will be the surviving company in this merger and will become a wholly owned subsidiary of Assertio Holdings. We refer to this merger as the "Merger." Following the consummation of the Merger, Zyla may be merged with and into a newly-formed Delaware limited liability company that is a direct wholly-owned subsidiary of Assertio Holdings, with the limited liability company surviving (the "Zyla LLC Conversion").

Upon completion of the Assertio Reorganization, Assertio Holdings will assume Assertio's listing on Nasdaq under Assertio Therapeutics' current ticker symbol, "ASRT." At the Effective Time, we expect that the former Assertio Therapeutics stockholders will hold approximately 68%, and that former Zyla stockholders will hold approximately 32% of the outstanding shares of Assertio Holdings Common Stock, calculated on a fully-diluted basis (treasury-stock method), immediately following the completion of the transactions.

Q:

Why is the Merger and the issuance of shares of Assertio Holdings Common Stock in the Merger being proposed?

A:

After careful consideration, Assertio Therapeutics' board of directors and Zyla's board of directors each determined that it is advisable and in the best interests of the Assertio Therapeutics stockholders and Zyla stockholders, respectively, to enter into the Merger Agreement and consummate the Merger and the other transactions contemplated thereby. Therefore, after such consideration, each of Assertio Therapeutics' board of directors and Zyla's board of directors approved the Merger Agreement and declared that the transactions are in the best interests of the Assertio Therapeutics stockholders and Zyla stockholders, respectively. In reaching their respective decisions, each board of directors consulted with its management, as well as its legal and financial advisors, and considered its fiduciary obligations, due diligence matters and the terms of the Merger Agreement. Each of Assertio's and Zyla's management believes that:

•

combining Assertio Therapeutics with Zyla is expected to establish the largest portfolio of branded NSAIDs in the United States, significantly enhancing the competitive position of the

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combined company by providing increased scale and broader commercial reach, and provide opportunities to expand into new therapeutic areas;

•

the combined company will have a stronger financial position than either Assertio Therapeutics or Zyla on a stand-alone basis, with attractive pro forma revenues, 2020 non-GAAP adjusted EBITDA margin expected to be greater than 25% and anticipated 2020 debt to EBITDA leverage of two times; and



•

the Merger of Zyla with Assertio is expected to provide potential synergies of at least $40 million annually resulting from the transaction, and the anticipated increase in salesforce productivity from complementary call points of Assertio Therapeutics and Zyla.

See "The Merger—Assertio's Reasons for the Merger and the Share Issuance" beginning on page 98 and "The Merger—Zyla's Reasons for the Merger" beginning on page 100.

Q:

What will happen if the Merger is completed?

A:

If the Merger is completed, Assertio Holdings will acquire Zyla through the merger of Merger Sub, a wholly-owned subsidiary of Assertio Holdings, with and into Zyla. Zyla will be the surviving corporation in the Merger. After the Merger, Zyla will continue as a wholly-owned subsidiary of Assertio Holdings. Following the consummation of the Merger, Zyla may be merged with and into a newly-formed Delaware limited liability company that is a direct, wholly-owned subsidiary of Assertio Holdings, with the limited liability company surviving, and Assertio Therapeutics may be merged with and into a newly-formed Delaware limited liability company that is a direct, wholly-owned subsidiary of Assertio Holdings, with the limited liability company surviving.

Q:

When will the Merger be completed?

A:

The Merger will be completed when the conditions described below under "The Agreement and Plan of Merger—Conditions to the Merger" are satisfied or waived, as permitted by the Merger Agreement and applicable law, and the related certificate of merger has been filed with the Secretary of State of the State of Delaware. Assertio and Zyla currently expect that the Merger can be completed by mid-2020. There can be no guarantee, however, as to when all conditions to the Merger will be satisfied and the completion of the Merger will occur, if at all. See "Risk Factors—Risks Relating to the Merger" beginning on page 34.

Q:

Who will be the directors of Assertio Holdings following the Merger?

A:

Upon the completion of the Merger, Assertio Holdings is expected to have a board of directors of nine directors, comprised of (a) Arthur Higgins, as the non-executive chairman of the board of directors, and Heather L. Mason, William T. McKee, Peter D. Staple, James L. Tyree, David E. Wheadon, each as an Assertio designee, and (b) Todd N. Smith, Timothy P. Walbert, as the lead independent director of the board of directors, and Andrea Heslin Smiley, each as a Zyla designee. The aforementioned board of directors will have an audit committee, a compensation committee and a nominating and corporate governance committee, in accordance with the rules of Nasdaq.

Q:

Who will be the Chief Executive Officer, Chief Financial Officer and Chief Operating Officer of Assertio Holdings following the Merger?

A:

Upon completion of the Merger, it is expected that Todd N. Smith will be Chief Executive Officer of Assertio Holdings, with Daniel A. Peisert as its Chief Financial Officer and Mark Strobeck as its Chief Operating Officer.

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Questions and Answers for Assertio Stockholders

Q:

Why am I receiving these materials?

A:

Assertio has made these materials available to you in connection with Assertio's solicitation of proxies for use at the Assertio Annual Meeting to be held on May 19, 2020 at 1:00 p.m. Central Time, and at any adjournments or postponements thereof. Assertio invites you to attend the Assertio Annual Meeting online and requests that you vote on the proposals described in this Joint Proxy Statement/Prospectus.

Q:

How do I attend the virtual Assertio Annual Meeting?

A:

The Assertio Annual Meeting will be a virtual meeting conducted exclusively via live webcast starting at 1:00 p.m. Central Time. You will be able to attend the Assertio Annual Meeting online, submit your questions during the meeting and vote your shares electronically at the meeting by going to https://www.cstproxy.com/assertiotx/2020 and entering your 16-digit control number, which is included on the proxy card or voting instruction form that you received. Because the Assertio Annual Meeting is completely virtual and being conducted via live webcast, stockholders will not be able to attend the meeting in person.

In light of the rapidly changing developments related to coronavirus (COVID-19), Assertio is pleased to offer its stockholders a completely virtual Assertio Annual Meeting, which provides worldwide access and communication, while protecting the health and safety of Assertio stockholders, directors, management and other stakeholders. Assertio is committed to ensuring that stockholders will be afforded the same rights and opportunities to participate as they would at an in-person meeting. Assertio will try to answer as many stockholder-submitted questions as time permits that comply with the Assertio Annual Meeting rules of conduct. However, Assertio reserves the right to edit profanity or other inappropriate language, or to exclude questions that are not pertinent to meeting matters or that are otherwise inappropriate. If substantially similar questions are received, Assertio will group such questions together and provide a single response to avoid repetition.

Q:

Do I need to register to attend the Assertio Annual Meeting?

A:

Yes. Pre-registration at https://www.cstproxy.com/assertiotx/2020 is recommended but is not required in order to attend.

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Any stockholder wishing to attend the virtual annual meeting should register for the meeting before it begins. To register for the virtual meeting, please follow these instructions as applicable to the nature of your ownership Assertio Common Stock:

•

If your shares are registered in your name with Assertio's transfer agent and you wish to attend the online-only virtual meeting, go to www.cstproxy.com/assertiotx/2020, enter the control number you received on your proxy card or notice of the meeting and click on the "Click here to preregister for the online meeting" link at the top of the page. Just prior to the start of the meeting you will need to log back into the meeting site using your control number. Pre-registration is recommended but is not required in order to attend.



•

Beneficial Stockholders (those holding shares through a stock brokerage account or by a bank or other holder of record) who wish to attend the virtual meeting must obtain a legal proxy by contacting their account representative at the bank, broker, or other nominee that holds their shares and email a copy (a legible photograph is sufficient) of their legal proxy to proxy@continentalstock.com. Beneficial shareholders who email a valid legal proxy will be issued a meeting control number that will allow them to register to attend and participate in the virtual meeting. After contacting Continental a beneficial holder will receive an e-mail prior to the meeting with a link and instructions for entering the virtual meeting. Beneficial stockholders should contact Continental at least five (5) business days prior to the meeting date.

Q:

Do I have the option to call in to the Assertio Annual Meeting instead of attending the live webcast?

Yes. Assertio's stockholders will also have the option to call in to the virtual meeting and listen by telephone by calling:

Optional telephone access (listen-only):
Within the U.S. and Canada: +1 866-894-0536 (toll-free)
Outside of the U.S. and Canada: +1 312-780-0854 (standard rates apply)

Passcode for telephone access:
25749471#

Q:

How do I submit questions for the Virtual Annual Meeting?

A:

Stockholders participating in the virtual meeting will be in a listen-only mode and will not be able to speak during the webcast. However, in order to maintain the interactive nature of the virtual meeting, virtual attendees are able submit questions before and during the meeting through the virtual meeting portal by typing in the "Submit a question" box. You can also submit any questions by emailing the company at corpgov@assertiotx.com.

Q:

Who do I contact if I am encountering difficulties attending the meeting online?

A:

If you encounter any difficulties during the check-in process or during the meeting, please call (917) 262-2373, and a technician will be ready to assist you.

Q:

What items will be voted on at the Assertio Annual Meeting?

A:

Stockholders will vote on the following items at the Annual Meeting:

1.

To approve the issuance of shares of Assertio Holdings Common Stock in connection with the Merger with Zyla, as described in greater detail in Chapter I of this Joint Proxy Statement/Prospectus.

2.

To elect the nine directors of Assertio named in this Joint Proxy Statement/Prospectus to serve until the 2021 Annual Meeting of Stockholders, or until their successors are duly elected and qualified, including in connection with the closing of the Merger.

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3.

To approve an increase in the number of shares available for issuance under Assertio's Amended and Restated 2014 Omnibus Incentive Plan, a copy of which is attached as Annex G to this Joint Proxy Statement/Prospectus. If the proposal to issue stock in connection with the Merger (Proposal 1) is not approved, the proposal to increase the number of shares available under Assertio's Amended and Restated 2014 Omnibus Incentive Plan will be automatically withdrawn.



4.

To approve an increase in the number of shares available for issuance under Assertio's Amended and Restated 2004 Employee Stock Purchase Plan, a copy of which is attached as Annex H to this Joint Proxy Statement/Prospectus.



5.

To approve an amendment to Assertio's certificate of incorporation to effect a reverse stock split at a ratio of not less than 1-for-2 and not greater than 1-for-4.



6.

To approve, on an advisory basis, the compensation of Assertio's named executive officers.



7.

To approve, on an advisory basis, Merger-related executive compensation arrangements.



8.

To ratify the appointment of Ernst & Young LLP as Assertio's independent registered public accounting firm for the fiscal year ended December 31, 2020.



9.

To approve the adjournment from time to time of the Assertio Annual Meeting if necessary to solicit additional proxies if there are not sufficient votes to adopt the proposal to issue stock in connection with the Merger (Proposal 1) at the time of the Assertio Annual Meeting or any adjournment or postponement thereof.



10.

To transact such other business as may properly come before the Assertio Annual Meeting and any adjournments or postponements thereof.

Q:

What are the Assertio board of director's voting recommendations?

A:

The Assertio board of directors recommends that you vote "FOR" each of the proposals and each director nominee.

Q:

How will I be affected by the Assertio Reorganization, the Merger and related share issuance?

A:

Under the Merger Agreement, the Assertio Reorganization will occur shortly prior to the Merger. After the Assertio Reorganization, each share of Assertio Therapeutics Common Stock will automatically be converted into one share of Assertio Holdings Common Stock. Assertio Holdings Common Stock will be listed on Nasdaq under Assertio Therapeutics' current ticker symbol, "ASRT." You will have the same number of shares of Assertio Holdings Common Stock as shares of Assertio Common Stock that you had immediately prior to the Assertio Reorganization. However, because Assertio Holdings will be issuing new shares of Assertio Holdings Common Stock to Zyla stockholders in the Merger, each outstanding share of Assertio Holdings Common Stock immediately prior to the Merger will represent a smaller percentage of the aggregate number of shares of Assertio Holdings Common Stock issued and outstanding after the Merger. For United States federal income tax purposes, it is intended that either (i) each of the Assertio Reorganization (together with the Assertio LLC Conversion, if any) and the Merger (together with the Zyla LLC Conversion, if any) qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, or the Code, or (ii) such transactions taken together qualify as a transaction governed by Section 351 of the Code. Assuming that each of the transactions so qualify, Assertio stockholders who exchange their Assertio Common Stock solely for shares of Assertio Holdings Common Stock pursuant to such transactions, in each case, will not recognize gain or loss for U.S. federal income tax purposes, other than gain or loss attributable to the receipt of cash in lieu of fractional shares of Assertio Holdings common stock. Tax matters are very complicated, and the tax consequences of the Merger to a particular Assertio stockholder will

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depend on such stockholder's circumstances. Accordingly, you should consult your tax advisor for a full understanding of the tax consequences of the Merger to you, including the applicability and effect of federal, state, local and foreign income and other tax laws. For more information, please see the section titled "Material U.S. Federal Income Tax Consequences of the Mergers."

Q:

What rights will I have as an Assertio Holdings stockholder following the completion of the Assertio Reorganization?

A:

Assertio Therapeutics and Assertio Holdings are both Delaware corporations, and, as part of the Assertio Reorganization, Assertio Holdings will be adopting substantially the same forms of Certificate of Incorporation and Bylaws of Assertio Therapeutics. Consequently, as a stockholder of Assertio Holdings following the completion of the Merger, you will have the same rights as an Assertio Holdings stockholder as you currently do as an Assertio Therapeutics stockholder.

Q:

What should I do now in order to vote on the proposals to be voted on at the Assertio Annual Meeting?

A:

After carefully reading and considering the information contained in this Joint Proxy Statement/Prospectus, please mark, sign and date the enclosed proxy card and return it in the enclosed postage-paid envelope as soon as possible so that your shares may be represented at the Assertio Annual Meeting. You may also cast your vote by attending the virtual Assertio Annual Meeting or by voting your shares via the Internet or by telephone by following the instructions on the back of your proxy card.

Q:

Who is entitled to vote and how do I vote?

A:

Only holders of record of Assertio Common Stock at the close of business on April 15, 2020 (the "Record Date") are entitled to attend (virtually) and to vote at the Assertio Annual Meeting. Each share is entitled to one vote on each matter presented at the Assertio Annual Meeting. Assertio stockholders do not have cumulative voting rights. As of the Record Date, there were 81,344,829 shares of common stock outstanding.

To ensure that your vote is recorded promptly, please vote as soon as possible, even if you plan to attend the virtual Assertio Annual Meeting in person. Assertio stockholders of record may vote online at the Assertio Annual Meeting by following the instructions available on the meeting website during the meeting or by mail, using the paper proxy card. All proxy cards received by Assertio that are properly signed and have not been revoked will be voted in accordance with the instructions contained in the proxy cards. If a signed proxy card is received which does not specify a vote or an abstention, the shares represented by that proxy card will be voted "FOR" each of the nominees to the Assertio board of directors listed on the proxy card under Proposal 2 and "FOR" Proposals 1, 3, 4, 5, 6, 7, 8, 9 and such other business as may come up. Beneficial owners may vote by telephone or online if their bank or broker makes those methods available, in which case the bank or broker will enclose the instructions with the proxy materials. For further instructions on voting, see your proxy card. If you vote by proxy using the paper proxy card, by telephone or online, the shares represented by the proxy will be voted in accordance with your instructions. Please note, however, that if your shares are held in "street name" and you wish to vote at the Assertio Annual Meeting, you must obtain a legal proxy issued in your name from the broker, bank or other nominee of record. Without a valid proxy, beneficial holders cannot vote at the Assertio Annual Meeting because their brokerage firm, bank or other financial institution may have already voted or returned a broker non-vote on their behalf.

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Q:

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

A:

Stockholder of Record. If your shares are registered directly in your name with Assertio's transfer agent, you are considered the stockholder of record with respect to those shares, and Assertio sent the proxy materials directly to you.

Beneficial Owner of Shares Held in Street Name. If your shares are held in an account at a brokerage firm, bank, broker-dealer or other similar organization, then you are the beneficial owner of shares held in "street name," and the proxy materials were forwarded to you by that organization. The organization holding your account is considered the stockholder of record for purposes of voting at the Assertio Annual Meeting. As a beneficial owner, you have the right to instruct that organization on how to vote the shares held in your account.

Q:

What if I submit a proxy and later change my mind?

A:

If you have given your proxy and later wish to revoke it, you may do so at any time before it is voted at the Assertio Annual Meeting by (a) delivering a proxy revocation or another duly executed proxy bearing a later date to Attn: Legal, Assertio at 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045 or (b) attending the virtual Assertio Annual Meeting and voting online. Attendance online at the Assertio Annual Meeting will not revoke a proxy unless the stockholder actually votes online during the virtual meeting.

Q:

What happens if other matters are raised at the Assertio Annual Meeting?

A:

Assertio is not aware, as of the date hereof, of any matters to be voted upon at the Assertio Annual Meeting other than those stated in this Joint Proxy Statement/Prospectus and the accompanying Notice of Annual Meeting of Stockholders. If any other matters are properly brought before the Assertio Annual Meeting, the enclosed proxy card gives discretionary authority to the persons named as proxies to vote the shares represented by the proxy card in their discretion.

Q:

What constitutes a quorum?

A:

A majority of the outstanding shares of Assertio's Common Stock as of the Record Date, present in person or by proxy and entitled to vote at the Assertio Annual Meeting, constitutes a quorum. Broker non-votes and abstentions will be counted for purposes of determining whether a quorum is present.

Q:

How is it determined whether a matter has been approved?

A:

Assuming a quorum is present, the approval of the matters specified in the Notice of Assertio Annual Meeting will be determined as follows:

•

For the election of directors in Proposal 2, each nominee will be elected if the number of votes cast for their election exceeds the number of votes cast against their election;

•

For the approval of an amendment to Assertio's certificate of incorporation in Proposal 5, the proposal must receive the affirmative vote of a majority of the total number of shares issued and outstanding as of the Record Date; and

•

For the approval of Proposals 1, 3, 4, 6, 7, 8, 9 and such other business as may come up, each proposal must receive the affirmative vote of a majority of the shares of Assertio's Common Stock, present online or by proxy and entitled to vote at the Assertio Annual Meeting.

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Q:

What vote of Assertio stockholders is required to approve the share issuance?

A:

The issuance of shares of Assertio Holdings Common Stock in the Merger requires the approval by a majority of the outstanding shares of Assertio Common Stock present and entitled to vote on the share issuance proposal at the Assertio Annual Meeting. This stockholder vote is required under the rules of Nasdaq because the aggregate number of shares of Assertio Holdings Common Stock to be issued to Zyla stockholders in the Merger will exceed 20% of the total number of shares of Assertio Holdings Common Stock issued and outstanding immediately prior to the completion of the Merger.

Q:

What are broker non-votes and abstentions?

A:

Broker non-votes occur when a broker has not received voting instructions from the beneficial owner of shares held in street name and the broker does not have discretionary authority to vote the shares. Abstentions occur when a stockholder who is present at the meeting, either in person on the meeting website or by proxy, affirmatively chooses not to vote on a proposal.

Q:

What effect does a broker non-vote or an abstention have?

A:

Broker non-votes and abstentions will be counted for purposes of determining whether a quorum is present. Broker non-votes and abstentions will have no effect on the outcome of the election of directors because broker non-votes and abstentions are not counted as votes cast for purposes of this proposal. Abstentions will have the same effect as a vote against any of the other matters specified in the Notice of Assertio Annual Meeting because abstentions are considered shares entitled to vote on these proposals. Broker non-votes will have no effect on such matters because they are not considered shares entitled to vote on these proposals. In order to minimize the number of broker non-votes, Assertio encourages you to provide voting instructions to the organization that holds your shares by carefully following the instructions provided in this Joint Proxy Statement/Prospectus.

Q:

What will happen if I abstain from voting on the share issuance proposal?

A:

Assuming the presence of a quorum for purposes of voting on the proposal to approve the issuance of shares of Assertio Holdings Common Stock in the Merger, an abstention will have the same effect as a vote against the proposal.

Q:

Do I have appraisal rights?

A:

No. Assertio stockholders will not have appraisal rights under Delaware law as a result of the Merger.

Q:

Where can I find the voting results of the Assertio Annual Meeting?

A:

The preliminary voting results will be announced at the Assertio Annual Meeting. The final voting results will be tallied by the Inspector of Election and published in a Current Report on Form 8-K, which Assertio is required to file with the SEC on or before the fourth business day following the Assertio Annual Meeting.

Q:

Who is paying for the cost of this proxy solicitation?

A:

The Assertio proxy card accompanying this Joint Proxy Statement/Prospectus is solicited by the Assertio board of directors. Assertio will pay all of the costs of soliciting proxies for the Assertio Annual Meeting. In addition to solicitation by mail, officers, directors and employees of Assertio may solicit proxies personally, or by telephone, without receiving additional compensation. Assertio has retained Innisfree M&A Incorporated (Innisfree), a proxy solicitation firm, to assist in the

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solicitation of proxies in connection with the Assertio Annual Meeting. Assertio will pay Innisfree customary fees in connection with such engagement, which Assertio expects will be approximately $50,000 plus reasonable expenses. Assertio, if requested, will also pay brokers, banks and other fiduciaries that hold shares of common stock for beneficial owners for their reasonable out-of-pocket expenses of forwarding these materials to stockholders.

Q:

Who should I contact if I have questions?

A:

If you have any questions about this Joint Proxy Statement/Prospectus, the Merger Agreement, the Merger or the issuance of shares of Assertio Holdings Common Stock in the Merger or if you need additional copies of this Joint Proxy Statement/Prospectus or the enclosed proxy card, you should contact the Secretary of Assertio at 100 South Saunders Road, Suite 300, Lake Forest, Illinois 60045. Additionally, any questions about the Merger, requests for additional copies of documents, or assistance voting your shares may be directed to Innisfree M&A Incorporated by telephone toll-free at 1-877-717-3930 (banks and brokers may call collect at 1-212-750-5833).

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Questions and Answers for Zyla Stockholders

Q:

What are Zyla stockholders being asked to consider and vote on?

A:

Zyla stockholders are being asked to consider and vote on the following three proposals:

•

to consider and vote on a proposal to adopt the Merger Agreement, which is referred to as the "Merger Agreement Proposal";

•

to consider and vote on a proposal to approve the adjournment from time to time of the Zyla Special Meeting if necessary to solicit additional proxies if there are not sufficient votes to approve the Merger Agreement Proposal at the time of the Zyla Special Meeting or any adjournment or postponement thereof, which is referred to as the "Zyla Adjournment Proposal"; and

•

to consider and vote on a proposal to approve, on an advisory (non-binding) basis, the compensation that will or may be paid or provided by Zyla to its named executive officers in connection with the Merger which is referred to in this notice as the "Zyla Compensation Advisory Proposal".

The adoption of the Merger Agreement by Zyla stockholders is a condition to the obligations of Zyla and Assertio to complete the Merger. Neither the approval of the Zyla Adjournment Proposal nor the Zyla Compensation Advisory Proposal is a condition to the obligations of Zyla or Assertio to complete the Merger.

Q:

Does Zyla's board of directors recommend that the Zyla stockholders approve the Merger Agreement Proposal?

A:

Yes. Zyla's board of directors determined that the Merger Agreement and the transactions contemplated by the Merger Agreement, including the Merger (together with the Zyla LLC Conversion, if any), are advisable, fair to and in the best interests of Zyla and its stockholders and recommends that Zyla stockholders vote "FOR" the Merger Agreement Proposal. See "Zyla Proposal 1: Adoption of the Merger Agreement" in this Joint Proxy Statement/Prospectus.

Q:

Does Zyla's board of directors recommend that the Zyla stockholders adopt the Zyla Adjournment Proposal?

A:

Yes. Zyla's board of directors recommends that Zyla stockholders vote "FOR" the Zyla Adjournment Proposal. See "Zyla Proposal 2: Adjournment of the Zyla Special Meeting" in this Joint Proxy Statement/Prospectus.

Q:

What is the Zyla Compensation Advisory Proposal and why am I being asked to vote on it?

A:

The SEC has adopted rules that require Zyla to seek an advisory (non-binding) vote on compensation that is tied to or based on completion of the Merger and that will or may be paid or provided by Zyla to its named executive officers in connection with the Merger.

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Q:

Does Zyla's board of directors recommend that Zyla stockholders approve, on an advisory (non-binding) basis, the Zyla Compensation Advisory Proposal?

A:

Yes. Zyla's board of directors recommends that Zyla stockholders vote "FOR" the Zyla Compensation Advisory Proposal. See "Zyla Proposal 3: Advisory Vote On Merger-Related Executive Compensation Arrangements" in this Joint Proxy Statement/Prospectus.

Q:

What happens if the Zyla Compensation Advisory Proposal is not approved?

A:

Approval of the Zyla compensation advisory proposal is not a condition to the obligations of Zyla or Assertio to complete the Merger. The vote is an advisory vote and is not binding on Zyla, the surviving company or Assertio. If the Merger is completed, the Merger-related compensation may be paid to Zyla's named executive officers to the extent payable in accordance with the terms of the compensation agreements and arrangements even if Zyla stockholders fail to approve the Zyla compensation advisory proposal.

Q:

What Zyla stockholder vote is required for the approval of each proposal at the Zyla Special Meeting?

A:

The following are the vote requirements for the proposals at the Zyla Special Meeting:

•

Adoption of the Merger Agreement:  The affirmative vote of the holders of a majority of the outstanding shares of common stock of Zyla, $0.001 par value per share (the "Zyla Common Stock") entitled to vote on this proposal. A Zyla stockholder's abstention from voting, the failure of a Zyla stockholder who holds their shares in "street name" through a broker, bank or other nominee to give voting instructions to that broker, bank or other nominee, or any other failure of a Zyla stockholder to vote, will have the same effect as a vote "AGAINST" this proposal.

•

Approval of the Zyla Adjournment Proposal (if necessary):

Quorum Not Present:    If a quorum is not present at the Zyla Special Meeting, the affirmative vote of holders of a majority of the shares of Zyla Common Stock present online or represented by proxy at the Zyla Special Meeting. A Zyla stockholder's abstention from voting on the Zyla Adjournment Proposal will have the same effect as a vote "AGAINST" this proposal. The failure of a Zyla stockholder who holds his or her shares in "street name" through a broker, bank or other nominee to give voting instructions to that broker, bank or other nominee, or any other failure of a Zyla stockholder to vote, will have no effect on the approval of this proposal.

Quorum Present:    If a quorum is present at the Zyla Special Meeting, the affirmative vote of the holders of a majority of the votes cast online or by proxy at the Zyla Special Meeting. A Zyla stockholder's abstention from voting on the Zyla Adjournment Proposal will have no effect on the approval of the proposal if a quorum is present. The failure of a Zyla stockholder who holds his, her or its shares in "street name" through a broker, bank or other nominee to give voting instructions to that broker, bank or other nominee, or any other failure of a Zyla stockholder to vote, will have no effect on the approval of this proposal.

•

Approval of the Zyla Compensation Advisory Proposal:  The affirmative vote of the holders of a majority of the votes cast online or by proxy at the Zyla Special Meeting. Accordingly, a Zyla stockholder's abstention from voting will have no effect on the approval of this proposal. The failure of a Zyla stockholder who holds his, her or its shares in "street name" through a broker, bank or other nominee to give voting instructions to that broker, bank or other nominee, or any other failure of a Zyla stockholder to vote, will have no effect on the approval of this proposal except to the extent it results in there being insufficient shares present at the Zyla Special Meeting to establish a quorum.

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Q:

How many votes must be present to hold the virtual Zyla Special Meeting?

A:

A quorum of Zyla stockholders is necessary to hold a valid special meeting. A quorum will be present if Zyla stockholders holding at least a majority of the outstanding Zyla shares entitled to vote are present at the Zyla Special Meeting online or represented by proxy. On the Zyla record date, there were 9,591,957 Zyla shares outstanding and entitled to vote. Thus, the holders of at least 4,795,979 Zyla shares must be present online or represented by proxy at the Zyla Special Meeting to achieve a quorum.

Your Zyla shares will be counted toward the quorum only if you submit a valid proxy (or one is submitted on your behalf by your broker, bank or other nominee) or if you vote online at the meeting. Abstentions and broker non-votes will be counted toward the quorum requirement. If there is no quorum, the holders of a majority of votes entitled to be cast by the Zyla stockholders entitled to vote at the meeting and present at the meeting online or represented by proxy may adjourn the meeting to another date.

Q:

Who can vote at the Zyla Special Meeting?

A:

Only Zyla stockholders of record at the close of business on April 15, 2020 will be entitled to vote at the Zyla Special Meeting. On the Zyla record date, there were 9,591,957 shares of Zyla Common Stock outstanding and entitled to vote.

•

Zyla Stockholder of Record: Shares Registered in Your Name:

If on April 15, 2020, your shares of Zyla Common Stock were registered directly in your name with Zyla's transfer agent, Computershare, then you are a stockholder of record of Zyla. As a stockholder of record of Zyla, you may vote online at the Zyla Special Meeting or vote by proxy. Whether or not you plan to join the Zyla Special Meeting, Zyla urges you to fill out and return the enclosed Zyla proxy card to ensure your vote is counted.

•

Beneficial Owner: Shares Registered in the Name of a Broker, Bank or Other Agent:

If on April 15, 2020, your shares of Zyla Common Stock were held, not in your name, but rather in an account at a brokerage firm, bank, dealer or other similar organization, then you are the beneficial owner of shares held in "street name" and the notice is being forwarded to you by that organization. The organization holding your account is considered to be the stockholder of record for purposes of voting at the Zyla Special Meeting. As a beneficial owner, you have the right to direct your broker or other agent regarding how to vote the Zyla shares in your account. You are also invited to join the Zyla Special Meeting. However, since you are not the Zyla stockholder of record, you may not vote your shares online at the meeting unless you request and obtain a valid proxy from your broker or other agent. As a beneficial owner, you may view the proxy materials at http://www.edocumentview.com/ZCOR.

Q:

How can I join and participate in the virtual Zyla Special Meeting?

A:

The virtual Zyla Special Meeting will be held on May 19, 2020 at 10:00 a.m., Eastern Time. Information on how to vote at the Zyla Special Meeting is discussed below.

•

To participate in the virtual Zyla Special Meeting visit http://www.envisionreports.com/ZCOR; the virtual meeting will begin promptly at 10:00 a.m., Eastern Time on May 19, 2020.

•

Enter your 15-digit control number, if applicable, as indicated.

•

Zyla stockholders may submit questions during the meeting.

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Q:

How can I vote my shares online at the virtual Zyla Special Meeting?

A:

If you are a Zyla stockholder of record, you may join the Zyla Special Meeting and vote via the virtual meeting website, http://www.envisionreports.com/ZCOR, where Zyla stockholders may vote and submit questions during the meeting. Please have your 15-Digit Control Number to join the Zyla Special Meeting. Instructions on how to join and participate via the Internet are posted at http://www.envisionreports.com/ZCOR.

Q:

What are "broker non-votes"?

A:

Broker non-votes occur when a beneficial owner of shares held in "street name" does not give instructions to the broker or nominee holding the shares as to how to vote on matters deemed "non-routine." Generally, if shares are held in street name, the beneficial owner of the shares is entitled to give voting instructions to the broker or nominee holding the shares. If the beneficial owner does not provide voting instructions, the broker or nominee can still vote the shares with respect to matters that are considered to be "routine," but not with respect to "non-routine" matters. To the extent that the proposals at the Zyla Special Meeting are considered to be not routine matters, your broker will not be able to exercise its discretion to vote uninstructed shares on any such proposals presented at the Zyla Special Meeting.

Q:

How many votes do I have?

A:

On each matter to be voted upon, you have one vote for each share of Zyla Common Stock you owned as of April 15, 2020.

Q:

How do I vote?

A:

The procedures for voting are as follows:

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record, you may vote online at the virtual Zyla Special Meeting, vote by proxy over the telephone, vote by proxy through the Internet, or vote by proxy using a proxy card. Whether or not you plan to join the virtual Zyla Special Meeting, Zyla urges you to vote by proxy to ensure your vote is counted. You may still join the virtual Zyla Special Meeting and vote online, even if you have already voted by proxy.

•

Online:  To vote online, join and vote at the virtual Zyla Special Meeting.



•

By Mail:  To vote using the proxy card, simply complete, sign and date the proxy card and return it promptly in the envelope provided. If you return your signed, completed and dated proxy card to Zyla before the Zyla Special Meeting, Zyla will vote your shares as you direct.



•

By Telephone:  To vote over the telephone, dial toll-free 1-800-652-VOTE (8683) using a touch-tone phone and follow the recorded instructions. Have your proxy available when you call. You will be asked to provide the Zyla number and control number from the notice. Your telephone vote must be received by the time the polls close at the Zyla Special Meeting on May 19, 2020 to be counted.



•

Via the Internet:  To vote through the Internet, go to http://www.envisionreports.com/ZCOR and follow the on-screen instructions. Your Internet vote must be received by the time the polls close at the Zyla Special Meeting on May 19, 2020 to be counted.

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Beneficial Owner: Shares Registered in the Name Bank or Other Agent

If you are a beneficial owner of shares registered in the name of your broker, bank, or other agent, you should have received a notice containing voting instructions from that organization rather than from Zyla. Simply follow the voting instructions in that notice to ensure that your vote is counted. To vote online at the virtual Zyla Special Meeting, you must obtain a valid proxy from your broker, bank or other agent. Follow the instructions included with these proxy materials, or contact your broker, bank or other agent to request a proxy form.

Q:

What happens if I do not vote?

A:

Stockholder of Record: Shares Registered in Your Name

If you are a stockholder of record and do not vote by duly signing, completing and returning your proxy card, by telephone, or online at the Zyla Special Meeting, your shares may or may not be voted.

Beneficial Owner: Shares Registered in the Name Bank or Other Agent

        See "What are broker non-votes?" above.

Q:

If I return a blank proxy, how will my shares be voted at the Zyla Special Meeting?

A:

If you sign your proxy card and return it without indicating how you would like to vote your shares, your proxy will be voted as Zyla's board of directors recommends, which is:

•

"FOR" the Merger Agreement Proposal;

•

"FOR" the Zyla Adjournment Proposal; and

•

"FOR" the Zyla Compensation Advisory Proposal.

If you do not give instructions to your broker, see "What are broker non-votes?" above.

Q:

Can I change my vote after submitting my proxy?

A:

Yes. You can revoke your proxy at any time before the final vote at the meeting.

Stockholder of Record: Shares Registered in Your Name

If you are the record holder of your shares, you may revoke your proxy in any one of the following ways:

•

You may submit another properly completed proxy card with a later date;



•

You may grant a subsequent proxy by telephone or through the Internet;



•

You may send a timely written notice that you are revoking your proxy to the Secretary at Zyla Life Sciences, 600 Lee Road, Suite 100, Wayne, PA 19087; or



•

You may join the virtual Zyla Special Meeting and vote online. Simply joining the meeting will not, by itself, revoke your proxy.

        Your most current proxy card or telephone or Internet proxy is the one that is counted.

Beneficial Owner: Shares Registered in the Name of Broker, Bank or Other Agent

If your shares are held by your broker, bank or other agent as a nominee, you should follow the instructions provided by your broker, bank or other agent.

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Q:

How can I submit a question for the Zyla Special Meeting?

If you want to submit a question during the Zyla Special Meeting, you may do so at http://www.envisionreports.com/ZCOR, entering your 15-digital control number, and following the on-screen instructions.

Q:

What happens if I sell my shares of Zyla Common Stock after the record date but before the Zyla Special Meeting?

A:

The record date for the Zyla Special Meeting (the close of business on April 15, 2020) is earlier than the date of the Zyla Special Meeting and earlier than the date that the Merger is expected to be completed. If you sell or otherwise transfer your shares of Zyla Common Stock after the record date but before the date of the Zyla Special Meeting, you will, unless the transferee obtains a proxy from you, retain your right to vote at the Zyla Special Meeting. However, you will not have the right to receive the Merger Consideration to be received by Zyla stockholders in the Merger. In order to receive the Merger Consideration, you must hold your shares immediately prior to completion of the Merger.

Q:

Are Zyla stockholders entitled to appraisal rights?

A:

Yes. Zyla stockholders who do not vote in favor of the adoption of the Merger Agreement are entitled to exercise appraisal rights under the Delaware General Corporation Law, which is referred to in this Joint Proxy Statement/Prospectus as the DGCL, in connection with the Merger if they take certain actions and meet certain conditions. For additional information, see the section entitled "Appraisal Rights or Dissenters' Rights of Zyla Stockholders" beginning on page 151 of this Joint Proxy Statement/Prospectus and the full text of Section 262, attached as Annex F to this Joint Proxy Statement/Prospectus. Because of the complexity of the DGCL relating to appraisal rights, if you wish to exercise your appraisal rights, Zyla encourages you to seek the advice of legal counsel. Failure to strictly comply with Section 262 may result in the loss of the right of appraisal.

Zyla stockholders considering seeking appraisal should be aware that the "fair value" of their shares of Zyla Common Stock as determined by the Delaware Court of Chancery under Section 262 could be greater than, the same as or less than the Merger Consideration.

Q:

Who is the inspector of the election for the Zyla Special Meeting?

A:

A representative of Computershare will serve as the independent inspector of election for the Zyla Special Meeting.

Q:

Will a proxy solicitor be used for the Zyla Special Meeting?

A:

No.

Q:

How can I find out the results of the voting at the Zyla Special Meeting?

A:

Preliminary voting results will be announced at the Zyla Special Meeting. In addition, final voting results will be published in a Current Report on Form 8-K that Zyla expects to file within four business days after the Zyla Special Meeting. If final voting results are not available to Zyla in time to file a Current Report on Form 8-K within four business days after the meeting, Zyla intends to file a Current Report on Form 8-K to publish preliminary results and, within four business days after the final results are known to us, file an additional Current Report on Form 8-K to publish the final results.

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Q:

Who is paying for this proxy solicitation?

A:

Zyla and Assertio will share equally the costs of printing and filing this Joint Proxy Statement/Prospectus and proxy cards. Arrangements will also be made with brokerage firms and other custodians, nominees and fiduciaries who are record holders of Zyla Common Stock and Assertio Common Stock for the forwarding of solicitation materials to the respective beneficial owners. Zyla and Assertio will reimburse these brokers, custodians, nominees and fiduciaries for the reasonable out-of-pocket expenses they incur in connection with the forwarding of solicitation materials. Assertio will pay Innisfree customary fees in connection with the engagement of Innisfree as proxy solicitor for its Annual Meeting, which Assertio expects will be approximately $50,000 plus reasonable expenses.

Q:

Should I send in my Zyla share certificates now?

A:

No. Zyla stockholders should not send in their share certificates at this time. After completion of the Merger, Assertio's exchange agent will send you a letter of transmittal and instructions for exchanging your shares of Zyla Common Stock for the Merger Consideration. The shares of Assertio Holdings' Common Stock you receive in the Merger will be issued in book-entry form and, unless otherwise requested, physical certificates will not be issued. See "The Agreement and Plan of Merger—Procedures for Exchange of Certificates; Fractional Shares; Dividends and Distributions" beginning on page 162 of this Joint Proxy Statement/Prospectus.

Q:

What are the intended U.S. federal income tax consequences of the Merger to Zyla United States stockholders?

A:

For U.S. federal income tax purposes, it is intended that either (i) each of the Assertio Reorganization (together with the Assertio LLC Conversion, if any) and the Merger (together with the Zyla LLC Conversion, if any) qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended, (the "Code") or (ii) such transactions taken together qualify as a transaction governed by Section 351 of the Code. Assuming that each of the transactions so qualify, Zyla stockholders who exchange their shares of Zyla Common Stock solely for shares of Assertio Holdings Common Stock pursuant to such transactions will not recognize gain or loss for U.S. federal income tax purposes, other than gain or loss attributable to the receipt of cash in lieu of fractional shares of Assertio Holdings Common Stock. Neither Assertio nor Zyla have sought, nor do they intend to seek, any ruling from the Internal Revenue Service (the "IRS") or opinion of counsel with respect to the qualification of the Assertio Reorganization or the Merger (together with the Zyla LLC Conversion, if any) as a reorganization within the meaning of Section 368(a) of the Code or as part of a transaction governed by Section 351 of the Code, and no assurance can be given that the IRS will agree with the views expressed herein, or that a court will not sustain any challenge by the IRS in the event of litigation. If the Assertio Reorganization or the Merger (together with the Zyla LLC Conversion, if any) do not so qualify, receipt of shares of Assertio Holdings Common Stock in exchange for shares of Assertio Common Stock or Zyla Common Stock in the Assertio Reorganization and the Merger would constitute a taxable exchange for U.S. federal income tax purposes and the corresponding tax consequences of the transactions could materially differ from those described here.

Tax matters are very complicated, and the tax consequences of the transactions to a particular Zyla stockholder will depend on such stockholder's circumstances. Accordingly, you should consult your tax advisor for a full understanding of the tax consequences of the transactions to you, including the applicability and effect of federal, state, local and foreign income and other tax laws. For more information, please see the section titled "Material U.S. Federal Income Tax Consequences of the Merger."

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Q:

Do persons involved in the Merger have interests that may conflict with mine as a Zyla stockholder?

A:

Some officers and directors of Zyla benefit from arrangements that provide them with interests in the Merger that are different from stockholders of Zyla generally, including, among others, service as an officer or director of the combined company following the closing of the Merger, the acceleration of equity award vesting, and continued indemnification. See "Interests of Zyla's Directors and Officers in the Merger" on page 138 for more information.

Q:

When are stockholder proposals and director nominations due for Zyla's next annual meeting?

A:

Stockholder proposals intended to be presented at the 2020 Annual Meeting of Zyla Stockholders must be received by Zyla no later than July 11, 2020 to be considered for inclusion in its annual meeting proxy statement. Upon receipt of any such proposal, Zyla will determine whether or not to include the proposal in the proxy statement and proxy in accordance with regulations governing the solicitation of proxies. Stockholders who wish to submit a proposal not intended to be included in Zyla's annual meeting proxy statement but to be presented at next year's annual meeting, or who propose to nominate a candidate for election as a director at that meeting, are required by Zyla's bylaws to provide notice of such proposal or nomination no later than the close of business on October 17, 2020, but no earlier than the close of business on September 17, 2020, to be considered for a vote at next year's annual meeting. Any proposal, nomination or notice must contain the information required by our bylaws and be delivered to Zyla's principal executive offices at Zyla Life Sciences, c/o Secretary, 600 Lee Road, Suite 100, Wayne, PA 19087.

Q:

If I am a stockholder of Zyla, who can help answer my questions?

A:

If you have questions about the Zyla Special Meeting or would like additional copies of this Joint Proxy Statement/Prospectus, you should contact Zyla's Secretary at 600 Lee Road, Suite 100, Wayne, PA 19087. Additionally, any questions about the Merger, requests for additional copies of documents, or assistance voting your shares may be directed to Innisfree M&A Incorporated by telephone toll-free at (877) 717-3930 (banks and brokers may call collect at (212) 750-5833.

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