Notice of Proposed Sale · 144

Alkermes plc

ALKSNASDAQEQUITYCurrent

Notice of Proposed Sale

Filed Oct 2, 2026Accepted Oct 2, 2026, 4:04 PM EDTFiling CIK 1675905Accession 0001964306-26-000464

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Structured filing — 144

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Notice of proposed sale. The proposed amounts below do not establish that a sale occurred.

Proposed-sale notice

Issuer: Alkermes plc.
Issuer CIK: 0001520262
SEC file number: 001-35299
Phone: 00-353-1-772-8000
Person for whose account securities are to be sold: Gaffin David Joseph
Relationships to issuer: Officer
Street: CONNAUGHT HOUSE
Street (continued): 1 BURLINGTON ROAD
City: DUBLIN 4
State / country code: L2
Postal code: 00000

Securities proposed for sale

Securities proposed for sale · 1 reported row
Security	Proposed units	Aggregate market value	Units outstanding	Approximate sale date	Exchange	Broker / market maker
Common Stock	2,034	83,455.02	167,763,272	10/02/2026	NASDAQ	Merrill Lynch

Broker / market maker — proposed row 1, entry 1

Name: Merrill Lynch
Street: 225 Liberty Street
Street (continued): Floor 37
City: New York
State / country code: NY
Postal code: 10281

Acquisition of securities to be sold

Acquisition of securities to be sold · 3 reported rows
Security	Acquired	Nature of acquisition	Acquired from	Amount acquired	Gift transaction	Payment date	Nature of payment
Common Stock	05/17/2014	Vesting of restricted stock unit award	Alkermes plc.	1,349	N	05/17/2014	Granted as part of issuer equity compensation plan
Common Stock	05/21/2015	Vesting of restricted stock unit award	Alkermes plc.	74	N	05/21/2015	Granted as part of issuer equity compensation plan
Common Stock	05/20/2015	Vesting of restricted stock unit award	Alkermes plc.	611	N	05/20/2015	Granted as part of issuer equity compensation plan

Sales reported in the preceding three months

Sales reported in the preceding three months · 4 reported rows
Seller	Security	Sale date	Amount sold	Gross proceeds
David Gaffin	Common Stock	06/04/2026	2,034	87,563.70
David Gaffin	Common Stock	07/06/2026	2,034	109,897.02
David Gaffin	Common Stock	08/03/2026	2,034	98,811.72
David Gaffin	Common Stock	09/03/2026	2,034	97,652.34

Seller — prior-sale row 1, entry 1

Name: David Gaffin
Street: CONNAUGHT HOUSE
Street (continued): 1 BURLINGTON ROAD
City: DUBLIN
State / country code: L2
Postal code: 00000

Seller — prior-sale row 2, entry 1

Name: David Gaffin
Street: CONNAUGHT HOUSE
Street (continued): 1 BURLINGTON ROAD
City: DUBLIN
State / country code: L2
Postal code: 00000

Seller — prior-sale row 3, entry 1

Name: David Gaffin
Street: CONNAUGHT HOUSE
Street (continued): 1 BURLINGTON ROAD
City: DUBLIN
State / country code: L2
Postal code: 00000

Seller — prior-sale row 4, entry 1

Name: David Gaffin
Street: CONNAUGHT HOUSE
Street (continued): 1 BURLINGTON ROAD
City: DUBLIN
State / country code: L2
Postal code: 00000

Prior-sale reporting

Nothing to report for the preceding three months: N

Notice signature

Notice date: 10/02/2026
Signed: David Gaffin
Plan adoption dates: 11/19/2025

Company context

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. The company has a portfolio of proprietary commercial products for the treatment of alcohol dependence, opioid dependence, schizophrenia, bipolar I disorder and narcolepsy. Alkermes’ pipeline includes late-stage clinical candidates in development for narcolepsy and idiopathic hypersomnia, and orexin 2 receptor agonists in early clinical development for other neurological disorders, including attention-deficit hyperactivity disorder (ADHD) and fatigue associated with multiple sclerosis and Parkinson’s disease. 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.

Current securities

ALKSNASDAQ · EQUITY · Current

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