Mallinckrodt and Endo Announce Significant Progress in Proposed Merger

S-4 Registration Statement Effective; HSR Waiting Period Expired

Irish High Court Approves Convening of Shareholder Meetings

Shareholder Vote Scheduled for June 13

Mallinckrodt plc (“Mallinckrodt”) and Endo, Inc. (OTCQX: NDOI) (“Endo”) today reported significant progress toward their proposed merger to create a global, scaled, diversified therapeutics leader.

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Mallinckrodt's registration statement on Form S-4, which includes a joint proxy statement for the special meetings of Mallinckrodt and Endo to consider and vote on the proposed transaction, became effective as of Thursday, May 8, 2025. In addition, the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 expired yesterday.

Mallinckrodt has received permission from the Irish High Court to schedule the special meetings of its shareholders for June 13, 2025. Mallinckrodt's headquarters are in Dublin, Ireland, which will serve as the combined company's global headquarters following the close, presently expected in the second half of this year. Endo has also scheduled its shareholder meeting to vote on the transaction for June 13, 2025.

“Exactly two months ago today, we announced the proposed merger and we are quite pleased by the rapid progress we have made toward creating an exciting new future for our shareholders, customers, employees, and, most importantly, the patients we serve,” said Siggi Olafsson, President and Chief Executive Officer of Mallinckrodt, who will become President and CEO of the combined company. “We remain excited about the potential benefits of this merger and for the opportunity to accelerate value creation through our unique portfolio of specialty and generic therapeutics.”

As announced on March 13, 2025, the proposed Mallinckrodt and Endo transaction envisions the spin-off of the combined generic pharmaceuticals businesses and Endo's sterile injectables business into a new standalone entity separate from the remaining branded pharmaceuticals business. Such a separation would be subject to approval by the combined company's Board of Directors and other conditions.

“This approach represents an exciting opportunity to create two leading companies that serve distinct customer sets,” said Scott Hirsch, Interim CEO of Endo. “Our businesses are highly complementary, and our strategy will create two larger and more diversified entities poised to unlock the full potential of both companies. Endo and Mallinckrodt both have talented teams that put patients first, and we look forward to bringing our organizations together to achieve even greater success.”

Under the terms of the agreement, Mallinckrodt shareholders will own 50.1% of the combined company on a pro forma basis, and Endo shareholders will receive a total of $80 million in cash (subject to potential increase) and will own 49.9% of the combined company on a pro forma basis.

Mallinckrodt will continue as the holding company for the combined business, and Endo will become a wholly owned subsidiary of Mallinckrodt.

About Mallinckrodt

Mallinckrodt is a global business consisting of multiple wholly owned subsidiaries that develop, manufacture, market and distribute specialty pharmaceutical products and therapies. The Company's Specialty Brands reportable segment's areas of focus include autoimmune and rare diseases in specialty areas like neurology, rheumatology, hepatology, nephrology, pulmonology and ophthalmology; neonatal respiratory critical care therapies; and gastrointestinal products. Its Specialty Generics reportable segment includes specialty generic drugs and active pharmaceutical ingredients. To learn more about Mallinckrodt, visitwww.mallinckrodt.com.

Mallinckrodt uses its website as a channel of distribution of important company information, such as press releases, investor presentations and other financial information. It also uses its website to expedite public access to time-critical information regarding the Company in advance of or in lieu of distributing a press release or a filing with theU.S. Securities and Exchange Commission(“SEC”) disclosing the same information. Therefore, investors should look to the Investor Relations page of the website for important and time-critical information. Visitors to the website can also register to receive automatic e-mail and other notifications alerting them when new information is made available on the Investor Relations page of the website.

About Endo

Endo is a diversified pharmaceutical company boldly transforming insights into life-enhancing therapies. Our passionate team members collaborate to develop and deliver these essential medicines. Together, we are committed to helping everyone we serve live their best life. Learn more atwww.endo.com or connect with us onLinkedIn.

No Offer or Solicitation

This communication is not intended to and shall not constitute an offer to buy or sell or the solicitation of an offer to buy or sell any securities, or a solicitation of any vote or approval, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities shall be made, except by means of a prospectus meeting the requirements of Section10 of the Securities Act of 1933, as amended.

Additional Information about the Combination and Where to Find It

In connection with the proposed transaction, Mallinckrodt has filed with the U.S. Securities and Exchange Commission (“SEC”) a registration statement on Form S-4 (as amended and as may be further amended from time to time, the “Registration Statement”), which was declared effective by the SEC on May 8, 2025, that includes a joint proxy statement of Mallinckrodt and Endo and that also constitutes a prospectus of Mallinckrodt ordinary shares. Each of Mallinckrodt and Endo may also file other relevant documents with the SEC regarding the proposed transaction. This document is not a substitute for the joint proxy statement/prospectus or Registration Statement or any other document that Mallinckrodt or Endo may file with the SEC. Mallinckrodt and Endo commenced mailing of the definitive joint proxy statement/prospectus to shareholders of Mallinckrodt and Endo, respectively, on or about May 12, 2025. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT, JOINT PROXY STATEMENT/PROSPECTUS, AND ANY OTHER RELEVANT DOCUMENTS THAT MAY BE FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. Investors and security holders will be able to obtain free copies of the Registration Statement and joint proxy statement/prospectus (if and when available) and other documents containing important information about Mallinckrodt, Endo, and the proposed transaction, once such documents are filed with the SEC through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Mallinckrodt will be available free of charge on Mallinckrodt's website at https://ir.mallinckrodt.com. Copies of the documents filed with the SEC by Endo will be available free of charge on Endo's website at https://investor.endo.com.

Participants in the Solicitation of Proxies

Mallinckrodt, Endo, and certain of their respective directors, executive officers, and other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction. Information about the directors and executive officers of Mallinckrodt, including a description of their direct or indirect interests, by security holdings or otherwise, is set forth in (i) Mallinckrodt's proxy statement for its 2025 Annual Meeting of Shareholders, which was filed with the SEC on April 03, 2025 (and which is available at https://www.sec.gov/ix?doc=/Archives/edgar/data/0001567892/000110465925031453/tm252514-2_def14a.htm), including under the headings “Our Director Nominees”, “Corporate Governance”, “Board of Directors and Board Committees,” “Compensation of Non-Employee Directors,” “Compensation of Executive Officers,” “Security Ownership and Reporting,” “Equity Compensation Plan Information” and “Proposals 1(A) Through 1(E): Election of Directors”, (ii) Mallinckrodt's Annual Report on Form 10-K for the fiscal year ended December 27, 2024, which was filed with the SEC on March 13, 2025 (and which is available at https://www.sec.gov/ix?doc=/Archives/edgar/data/1567892/000156789225000010/mnk-20241227.htm), including under the headings “Item 10. Directors, Executive Officers and Corporate Governance”, “Item 11. Executive Compensation”, “Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters”, “Item 13. Certain Relationships and Related Transactions and Director Independence”, and (iii) to the extent holdings of Mallinckrodt's securities by its directors or executive officers have changed since the amounts set forth in Mallinckrodt's proxy statement for its 2025 Annual Meeting of Shareholders, such changes have been or will be reflected on Initial Statement of Beneficial Ownership of Securities on Form 3, Statement of Changes in Beneficial Ownership on Form 4, or Annual Statement of Changes in Beneficial Ownership on Form 5 filed with the SEC, which are available at EDGAR Search Results (https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0001567892&type=&dateb=&owner=only&count=40&search_text=).

Information about the directors and executive officers of Endo, including a description of their direct or indirect interests, by security holdings or otherwise, is set forth in (i) the Registration Statement, (ii) Endo's Annual Report on Form 10-K for the fiscal year ended December 31, 2024, which was filed with the SEC on March 13, 2025 (and which is available at https://www.sec.gov/ix?doc=/Archives/edgar/data/2008861/000200886125000007/ndoi-20241231.htm), including under the headings “Item 10. Directors, Executive Officers and Corporate Governance”, “Item 11. Executive Compensation”, “Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters”, “Item 13. Certain Relationships and Related Transactions and Director Independence”, and (iii) to the extent holdings of Endo's securities by its directors or executive officers have changed since the amounts set forth in the Registration Statement, such changes have been or will be reflected on Initial Statement of Beneficial Ownership of Securities on Form 3, Statement of Changes in Beneficial Ownership on Form 4, or Annual Statement of Changes in Beneficial Ownership on Form 5 filed with the SEC, which are available at EDGAR Search Results (https://www.sec.gov/cgi-bin/browse-edgar?action=getcompany&CIK=0002008861&type=&dateb=&owner=only&count=40&search_text=). Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, is contained in the joint proxy statement/prospectus and will be contained in other relevant materials to be filed with the SEC regarding the proposed transaction when such materials become available. Investors should read these materials carefully before making any voting or investment decisions. You may obtain free copies of these documents from Mallinckrodt or Endo using the sources indicated above.

Information Regarding Forward-Looking Statements

Statements in this communication that are not strictly historical may be “forward-looking” statements within the meaning of the Private Securities Litigation Reform Act of 1995, and involve a number of risks and uncertainties.

There are a number of important factors that could cause actual events to differ materially from those suggested or indicated by such forward-looking statements and you should not place undue reliance on any such forward-looking statements. These factors include risks and uncertainties related to, among other things:

(i) transaction-related risks, including the parties' ability to successfully integrate our business andEndo's business and unanticipated costs of such integration, which may result in the combined company not operating as effectively and efficiently as expected; uncertainties related to a future separation of the combined generics pharmaceuticals businesses of Mallinckrodt and Endo and Endo's sterile injectables business; the risk that the expected benefits and synergies of the proposed transactions may not be fully realized in a timely manner, or at all; the risk associated with Mallinckrodt's and Endo's ability to obtain the approval of their shareholders and stockholders, respectively, required to consummate the proposed business combination transaction; uncertainty regarding the timing of the closing of the proposed business combination transaction; the risk that the conditions to the proposed business combination transaction may not be satisfied (or waived to the extent permitted by law) on a timely basis or at all or the failure of the proposed business combination transaction to close for any other reason or to close on the anticipated terms, including the intended tax treatment; the risk that any regulatory approval, consent or authorization that may be required for the proposed business combination transaction may not be obtained or may be obtained subject to conditions that are not anticipated; the occurrence of any event, change or other circumstance that could give rise to the termination of the proposed business combination transaction; unanticipated difficulties, liabilities or expenditures relating to the proposed transactions; the effect of the announcement, pendency or completion of the proposed transactions on the parties' business relationships and business operations generally; certain restrictions on the ability of Mallinckrodt and Endo to pursue certain business activities or strategic transactions during the pendency of the proposed business combination transaction; the effect of the announcement, pendency or completion of the proposed transactions on the long-term value of Mallinckrodt's ordinary shares and Endo's common stock; risks that the proposed transactions may disrupt current plans and operations of Mallinckrodt and Endo and their respective management teams and potential difficulties in hiring, retaining and motivating employees as a result of the proposed transactions; risks related to our increased indebtedness as a result of the proposed business combination transaction; significant transaction costs related to the proposed business combination transaction; potential litigation relating to the proposed transactions that could be instituted against Mallinckrodt, Endo or their respective officers or directors; rating agency actions and Mallinckrodt's and Endo's ability to access short- and long-term debt markets on a timely and affordable basis; and risks related to the financing in connection with the transaction;(ii) risks related toMallinckrodt's business, including potential changes in Mallinckrodt's business strategy and performance; Mallinckrodt's initiative to explore a variety of potential divestiture, financing and other transactional opportunities; the exercise of contingent value rights by the Opioid Master Disbursement Trust II (the “Trust”); governmental investigations and inquiries, regulatory actions, and lawsuits, in each case related to Mallinckrodt or its officers; Mallinckrodt's contractual and court-ordered compliance obligations that, if violated, could result in penalties; compliance with and restrictions under the global settlement to resolve all opioid-related claims; matters related to Acthar Gel, including the settlement with governmental parties to resolve certain disputes and compliance with and restrictions under the related corporate integrity agreement; the ability to maintain relationships with Mallinckrodt's suppliers, customers, employees and other third parties following the emergence from the 2023 bankruptcy proceedings; scrutiny from governments, legislative bodies and enforcement agencies related to sales, marketing and pricing practices; pricing pressure on certain of Mallinckrodt's products due to legal changes or changes in insurers' or other payers' reimbursement practices resulting from recent increased public scrutiny of healthcare and pharmaceutical costs; the reimbursement practices of governmental health administration authorities, private health coverage insurers and other third-party payers; complex reporting and payment obligations under the Medicare and Medicaid rebate programs and other governmental purchasing and rebate programs; cost containment efforts of customers, purchasing groups, third-party payers and governmental organizations; changes in or failure to comply with relevant laws and regulations; any undesirable side effects caused by Mallinckrodt's approved and investigational products, which could limit their commercial profile or result in other negative consequences; Mallinckrodt's and its partners' ability to successfully develop, commercialize or launch new products or expand commercial opportunities of existing products, including Acthar Gel (repository corticotropin injection) SelfJect™ and the INOmax Evolve DS delivery system; Mallinckrodt's ability to successfully identify or discover additional products or product candidates; Mallinckrodt's ability to navigate price fluctuations and pressures, including the ability to achieve anticipated benefits of price increases of its products; competition; Mallinckrodt's ability to protect intellectual property rights, including in relation to ongoing and future litigation; limited clinical trial data for Acthar Gel; the timing, expense and uncertainty associated with clinical studies and related regulatory processes; product liability losses and other litigation liability; material health, safety and environmental laws and related liabilities; business development activities or other strategic transactions; attraction and retention of key personnel; the effectiveness of information technology infrastructure, including risks of external attacks or failures; customer concentration; Mallinckrodt's reliance on certain individual products that are material to its financial performance; Mallinckrodt's ability to receive sufficient procurement and production quotas granted by theU.S. Drug Enforcement Administration; complex manufacturing processes; reliance on third-party manufacturers and supply chain providers and related market disruptions; conducting business internationally; Mallinckrodt's significant levels of intangible assets and related impairment testing; natural disasters or other catastrophic events; Mallinckrodt's substantial indebtedness and settlement obligation, its ability to generate sufficient cash to reduce its indebtedness and its potential need and ability to incur further indebtedness; restrictions contained in the agreements governing Mallinckrodt's indebtedness and settlement obligation on Mallinckrodt's operations, future financings and use of proceeds; Mallinckrodt's variable rate indebtedness; Mallinckrodt's tax treatment by theInternal Revenue Serviceunder Section 7874 and Section 382 of the Internal Revenue Code of 1986, as amended; future changes to applicable tax laws or the impact of disputes with governmental tax authorities; the impact of Irish laws; the impact on the holders of Mallinckrodt's ordinary shares if Mallinckrodt were to cease to be a reporting company in the United States; the comparability of Mallinckrodt's post-emergence financial results and the projections filed with theBankruptcy Court; and the lack of comparability of Mallinckrodt's historical financial statements and information contained in its financial statements after the adoption of fresh-start accounting following emergence from the 2023 bankruptcy proceedings; and(iii) risks related toEndo's business, including future capital expenditures, expenses, revenues, economic performance, financial conditions, market growth and future prospects; Endo changes in competitive, market or regulatory conditions; changes in legislation or regulations; global political changes, including those related to the new U.S. presidential administration; Endo's use of artificial intelligence and data science; the ability to obtain and maintain adequate protection for intellectual property rights; the impacts of competition such as those related to XIAFLEX®; the timing and uncertainty of the results of both the research and development and regulatory processes; health care and cost containment reforms, including government pricing, tax and reimbursement policies; litigation; the performance including the approval, introduction and consumer and physician acceptance of current and new products; the performance of third parties upon whom Endo relies for goods and services; issues associated with Endo's supply chain; Endo's ability to develop and expand its product pipeline and to launch new products and to continue to develop the market for XIAFLEX® and other branded, sterile injectable or generic products; the effectiveness of advertising and other promotional campaigns; and the timely and successful implementation of business development opportunities and/or any other strategic priorities.

The Registration Statement on Form S-4 filed with the SEC describes additional risks in connection with the proposed transaction. While the list of factors presented here is, and the list of factors presented in the Registration Statement on Form S-4 are, considered representative, no such list should be considered to be a complete statement of all potential risks and uncertainties. For additional information about other factors that could cause actual results to differ materially from those described in the forward-looking statements, please refer to Mallinckrodt's most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q, and other filings with theSEC, which are available from theSEC'swebsite (www.sec.gov) and Mallinckrodt's website (www.mallinckrodt.com) and Endo's most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q and other filings with theSEC, which are available from theSEC'swebsite (www.sec.gov) and Endo's website (www.endo.com). There may be other risks and uncertainties that we are unable to predict at this time or that we currently do not expect to have a material adverse effect on our business.

The forward-looking statements made herein speak only as of the date hereof and Mallinckrodt and Endo do not assume any obligation to update or revise any forward-looking statement, whether as a result of new information, future events and developments or otherwise, except as required by law. Given these uncertainties, one should not put undue reliance on any forward-looking statements.

Mallinckrodt Contacts

Investor RelationsBryan ReasonsExecutive Vice President and Chief Financial Officerbryan.reasons@mnk.com

MediaMichael Freitag/Aaron Palash/Aura ReinhardJoele Frank,Wilkinson Brimmer Katcher212-355-4449

Government Affairs & Patient AdvocacyDerek NatenVice President, Government Affairs202-459-4143derek.naten@mnk.com

Endo Contacts

Investor RelationsJuan Avendanoinvestor.relations@endo.com

MediaLinda Hussmedia.relations@endo.com

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SOURCE Mallinckrodt plc

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