Alkermes Contacts: For Investors: Sandy Coombs +1 781 609 6377 For Media: Katie Joyce +1 781 249 8927 Alkermes plc Announces Agreement to Acquire Avadel Pharmaceuticals plc NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION, I

Alkermes plc Announces Agreement to Acquire

Avadel Pharmaceuticals plc

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION, IN

WHOLE OR IN PART, IN, INTO OR FROM ANY JURISDICTION WHERE TO DO SO WOULD CONSTITUTE A VIOLATION OF THE RELEVANT LAWS OR REGULATIONS

OF SUCH JURISDICTION

THIS ANNOUNCEMENT IS BEING MADE PURSUANT

TO RULE 2.7 OF THE IRISH TAKEOVER RULES

Revenue Growth Profile and Diversifies Alkermes' Commercial Portfolio with New High Growth Product, LUMRYZ (Sodium Oxybate)

Alkermes' Commercial Entry into Sleep Medicine Market and Provides Strong Foundation for Potential Launch of Alixorexton

to be Immediately Accretive and Enhance Profitability Upon Closing

the Combined Organization to Accelerate Innovation and Expand its Leadership in Development of Treatments for Sleep Disorders and Other

Neurological Disorders

Valued at $18.50 per Share in Cash with a CVR for an Additional $1.50 per Share in Cash, for Total Consideration of up to $20.00 per

share, or a Transaction Value of up to $2.1 Billion

to Host Conference Call and Webcast on Oct. 22, 2025 at 8:00 a.m. ET

DUBLIN, October 22, 2025 -

Alkermes plc (Nasdaq: ALKS) ("Alkermes") and Avadel Pharmaceuticals plc (Nasdaq: AVDL) ("Avadel") today announced

that the companies have entered into a definitive agreement under which Alkermes will acquire Avadel, a commercial-stage biopharmaceutical

company, for total transaction consideration of up to $20.00 per share in cash, which values Avadel at approximately $2.1 billion and

represents a premium of 38% to the weighted average trading price of Avadel over the three months prior to today's announcement

and a premium of 12% to Avadel's closing price on Oct. 21, 2025 (being the last business day prior to publication of this

announcement). The transaction has been approved by the boards of directors of both companies and is expected to close in the first

The planned acquisition adds Avadel's FDA-approved

product, LUMRYZ (sodium oxybate) for the treatment of cataplexy or excessive daytime sleepiness in patients over 7 years of age

with narcolepsy, to Alkermes' commercial portfolio. This strategic move accelerates Alkermes' entry into the sleep medicine

market and enhances its ability to unlock the full potential of its late-stage development pipeline focused on central disorders of hypersomnolence.

The transaction is expected to be immediately accretive upon closing and represents a compelling financial and strategic opportunity,

leveraging Alkermes' existing commercial expertise and operational infrastructure and adding new capabilities in rare disease.

Avadel is a recognized innovator in the sleep

medicine space, committed to addressing significant unmet needs for patients. Since launching LUMRYZ in 2023, Avadel has successfully

built and scaled a commercial organization that has driven strong demand. Approximately 3,100 patients were on LUMRYZ therapy

as of June 30, 2025, with new patient starts outpacing the twice-nightly mixed-salts competitor by more than 2:1 since July 2023.

With net revenues of $265 - $275 million expected in 2025 and an estimated population of >50,000 oxybate-eligible narcolepsy

patients in the United States, LUMRYZ has been on a robust growth trajectory, with significant opportunity for growth ahead.

"This transaction represents a pivotal

step in Alkermes' strategic evolution. With the acquisition of Avadel, we are able to accelerate our commercial entry into the

sleep medicine market at a critical inflection point as we prepare to advance alixorexton into a phase 3 program in narcolepsy. Avadel's

innovative portfolio, commercial capabilities and dedicated employees provide a strong foundation for growth in this therapeutic area.

Enabled by our strong balance sheet, this all-cash transaction enhances our revenue growth profile and is expected to be immediately

accretive, reinforcing our commitment to delivering long-term value for shareholders," said Richard Pops, Chief Executive Officer

"This transaction represents a compelling

outcome for our shareholders and a powerful validation of our strategy, execution, commercial capabilities and the differentiated value

of LUMRYZ . We've built a company deeply committed to transforming the lives of people living with narcolepsy, and I'm

incredibly proud of what our team has accomplished. Alkermes shares our passion for innovation and patient impact and, together, we will

continue this important work on behalf of people living with central disorders of hypersomnolence," said Greg Divis, Chief Executive

Under the terms of and subject to the conditions

set out in the Transaction Agreement, Alkermes will acquire all outstanding ordinary shares of Avadel for $18.50 per share, payable

in cash at closing. In addition, Alkermes will provide Avadel shareholders with a non-transferable contingent value right (CVR) entitling

holders to a potential additional cash payment of $1.50 per share, contingent upon final FDA approval of LUMRYZ for the treatment

of idiopathic hypersomnia in adults by the end of 2028. Taken together, this potential per share acquisition price represents an enterprise

value of approximately $2.1 billion. Alkermes expects to finance the acquisition with cash on hand, supplemented by the issuance of new

The transaction, which has been approved by the

boards of directors of both Alkermes and Avadel, is expected to close in the first quarter of 2026, subject to the Conditions set out

in Appendix III of this Announcement, including certain regulatory approvals and approvals by Avadel's shareholders.

J.P. Morgan is acting as exclusive financial

advisor to Alkermes, and Paul, Weiss, Rifkind, Wharton & Garrison LLP and McCann FitzGerald LLP are acting as legal counsel

to Alkermes for the transaction. J.P. Morgan has provided fully committed financing to Alkermes in support of the transaction. Cleary

Gottlieb Steen & Hamilton LLP is acting as legal counsel to Alkermes for the financing. Morgan Stanley and Goldman Sachs are

acting as financial advisors to Avadel, and Goodwin Procter LLP and Arthur Cox LLP are acting as legal counsel to Avadel.

Alkermes will host a conference call and webcast

with accompanying slides at 8:00 a.m. ET (1:00 p.m. BST) on Wednesday, Oct. 22, 2025, to discuss the planned acquisition.

The webcast may be accessed on the Investors section of Alkermes' website at www.alkermes.com. The conference call may be accessed

by dialing +1 877 407 2988 for U.S. callers and +1 201 389 0923 for international callers. In addition, a replay of the conference call

may be accessed by visiting Alkermes' website.

Alkermes plc (Nasdaq: ALKS), a mid-cap growth

and value equity, is a global biopharmaceutical company that seeks to develop innovative medicines in the field of neuroscience. Alkermes

has a portfolio of proprietary commercial products for the treatment of alcohol dependence, opioid dependence, schizophrenia and bipolar

I disorder, and a pipeline of clinical and preclinical candidates in development for neurological disorders, including narcolepsy and

idiopathic hypersomnia. Headquartered in Ireland, Alkermes also has a corporate office and research and development center in Massachusetts

and a manufacturing facility in Ohio. For more information, please visit Alkermes' website at www.alkermes.com.

About Avadel Pharmaceuticals plc

Avadel Pharmaceuticals plc (Nasdaq: AVDL)

is a biopharmaceutical company focused on transforming medicines to transform lives. Avadel's approach includes applying innovative

solutions to the development of medications that address the challenges patients face with current treatment options. Avadel's

commercial product, LUMRYZ , was approved by the U.S. Food & Drug Administration (FDA) as the first and only

once-at-bedtime oxybate for extended-release oral suspension for the treatment of cataplexy or excessive daytime sleepiness (EDS) in

patients 7 years and older with narcolepsy. For more information, please visit Avadel's website at www.avadel.com.

This summary should be read in conjunction with,

and is subject to, the full text of the remainder of the Rule 2.7 Announcement set out below (including its appendices). The Acquisition

is subject to the conditions set out in Appendix III to this Announcement and the further terms to be set out in the Transaction Agreement.

The sources and bases of information contained in this Announcement are set out in Appendix I of this Announcement. Certain definitions

and expressions used in this Announcement are set out in Appendix II of this Announcement. A copy of the Transaction Agreement entered

into between Alkermes and Avadel, which relates to, among other things, the implementation of the acquisition, is set out in Appendix

IV of this Announcement. Finally, Appendix V contains the Company FY25 Profit Forecast and the Company Q3 2025 Profit Forecast and the

confirmation required by the Company Directors in respect thereof pursuant to Rule 28.1(c)(i) of the Takeover Rules.

The release, publication or distribution of this

Announcement in or into jurisdictions other than Ireland and the United States may be restricted by Law and therefore any persons who

are subject to the Law of any jurisdiction other than Ireland and the United States should inform themselves about, and observe, any

applicable legal or regulatory requirements. In particular, the ability of persons who are not resident in Ireland or the United States,

to vote their Avadel shares with respect to the Scheme at the Scheme Meeting, or to appoint another person as proxy to vote at the Scheme

Meeting on their behalf, may be affected by the Laws of the relevant jurisdictions in which they are located. Any failure to comply with

the applicable legal or regulatory requirements may constitute a violation of the Laws of any such jurisdiction. To the fullest extent

permitted by applicable Law, the Alkermes and Avadel persons involved in the proposed transaction disclaim any responsibility or liability

for the violation of such restrictions by any person.

This Announcement has been prepared for the purpose

of complying with the Laws of Ireland and the Irish Takeover Rules, 2022 (the "Takeover Rules") and the information disclosed

herein may not be the same as that which would have been disclosed if this Announcement had been prepared in accordance with the Laws

of jurisdictions outside of Ireland.

NOT FOR RELEASE, PUBLICATION OR DISTRIBUTION