X0202 SCHEDULE 13D/A 0000899140-22-000088 0001577524 XXXXXXXX LIVE 16 Ordinary Shares, par value 50 pence per share 08/25/2026 false 0000897448 023111206 Amarin Corporation PLC/UK

One Central Plaza, 5th Floor 36 Dame Street Dublin 2 L2 D02 EF64

Alexander J Denner 203-302-2330 Sarissa Capital Management LP 500 West Putnam Avenue, Suite 400 Greenwich CT 06830 0001577524 N Sarissa Capital Management LP WC DE 0 25743900 0 25743900 25743900 N 6.09 PN 0001361754 N Alexander J Denner AF X1 0 25743900 0 25743900 25743900 N 6.09 IN Ordinary Shares, par value 50 pence per share Amarin Corporation PLC/UK One Central Plaza, 5th Floor 36 Dame Street Dublin 2 L2 D02 EF64 This Amendment No. 16 to Schedule 13D ("Amendment No. 16") relates to American Depositary Shares ("ADS(s)"), each ADS presently representing twenty ordinary shares, par value 50 pence per share (the "Ordinary Shares"), issued by Amarin Corporation plc, a company incorporated under the laws of England and Wales (the "Issuer"), and amends the initial statement on Schedule 13D filed with the Securities and Exchange Commission (the "SEC") on January 24, 2022 (the "Initial Schedule 13D"), as amended by Amendment No. 1 to Schedule 13D filed on June 3, 2022, Amendment No. 2 to Schedule 13D filed on June 16, 2022, Amendment No. 3 to Schedule 13D filed on October 11, 2022, Amendment No. 4 to Schedule 13D filed on January 11, 2023, Amendment No. 5 to Schedule 13D filed on January 19, 2023, Amendment No. 6 to Schedule 13D filed on February 8, 2023, Amendment No. 7 to Schedule 13D filed on February 10, 2023, Amendment No. 8 to Schedule 13D filed on February 14, 2023, Amendment No. 9 to Schedule 13D filed on February 15, 2023, Amendment No. 10 to Schedule 13D filed on February 21, 2023, Amendment No. 11 to Schedule 13D filed on February 27, 2023, Amendment No. 12 to Schedule 13D filed on February 28, 2023, Amendment No. 13 to Schedule 13D filed on September 5, 2023, Amendment No. 14 to Schedule 13D filed on December 5, 2023 and Amendment No. 15 to Schedule 13D filed on March 25, 2025 (the Initial Schedule 13D as so amended, the "Schedule 13D"). All capitalized terms contained herein but not otherwise defined shall have the meanings ascribed to such terms in the Schedule 13D. This Amendment No. 16 is being filed to amend Item 2(b), Item 5(a), Item 5(c) and Item 7 as follows: The address of the principal business and principal office of each of the Reporting Persons is c/o Sarissa Capital Management LP, 500 West Putnam Avenue, Suite 400, Greenwich, CT 06830. The Reporting Persons may be deemed to beneficially own, in the aggregate, 25,743,900 Ordinary Shares representing approximately 6.09% of the outstanding Ordinary Shares. Percentages of the outstanding Ordinary Shares are based upon the 422,456,685 Ordinary Shares outstanding as of July 24, 2026, including 20,632,560 Ordinary Shares held as ADSs, each representing 20 Ordinary Shares, as set forth in the Form 10-Q of the Issuer filed with the SEC on July 29, 2026 for the quarterly period ended June 30, 2026. Within the past 60 days, the Reporting Persons have transacted in the Issuer's securities as set forth in Exhibit 17, attached hereto and incorporated herein by reference. Material to Be Filed as Exhibits. Item 7 is hereby amended to include the following: Exhibit 17 Transactions in Securities Sarissa Capital Management LP /s/ Alexander J Denner 08/27/2026 Alexander J Denner /s/ Alexander J Denner 08/27/2026