Sec Form 4 Filing - Ketchum Steven B @ AMARIN CORP PLC\UK - 2021-12-31

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Ketchum Steven B 2. Issuer Name and Ticker or Trading Symbol AMARIN CORP PLC\UK [ AMRN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Scientific Officer (Last) (First) (Middle) C/O AMARIN PHARMA, INC., 440 US HIGHWAY 22 3. Date of Earliest Transaction (MM/DD/YY) 12/31/2021 (Street) BRIDGEWATER, NJ08807 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Ordinary Shares( 1 ) 12/31/2021 M( 2 ) 47,767 A 502,908 D Ordinary Shares( 1 ) 12/31/2021 F( 4 ) 24,433 D $ 3.35 478,475( 5 ) D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Restricted Stock Units( 6 ) $ 0 12/31/2021 M 47,767 ( 2 ) ( 3 ) Ordinary Shares( 1 ) 47,767 $ 0 95,533 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Ketchum Steven B C/O AMARIN PHARMA, INC. 440 US HIGHWAY 22 BRIDGEWATER, NJ08807 Chief Scientific Officer Signatures /s/ Michael W. Kalb, by power of attorney 01/04/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The Ordinary Shares may be represented by American Depositary Shares, each of which currently represents one Ordinary Share. ( 2 )On January 4, 2021, the Reporting Person was granted 143,300 Restricted Stock Units ("RSUs") under the Amarin Corporation plc 2020 Stock Incentive Plan (the "2020 Plan"). These RSUs vest in three equal installments on each of December 31, 2021, December 31, 2022 and December 31, 2023. The first vesting event occurred on December 31, 2021. ( 3 )Not applicable. ( 4 )Represents withholding by the Issuer of shares in respect of tax liability incident to the vesting of a security issued in accordance with Rule 16b-3, and not a market sale of securities. ( 5 )Please see the section titled "Remarks" below for additional information. ( 6 )Each RSU represents a contingent right to receive one Ordinary Share or cash in lieu thereof at the Issuer's discretion.

Remarks: As of the date of this Form 4, the Reporting Person owns or holds the right to acquire an aggregate of 1,387,794 Ordinary Shares of the Issuer in the form of Ordinary Shares, stock options and RSUs outstanding under the Issuer's stock incentive plans, including but not limited to certain performance-based RSUs that are earned only if certain pre-defined operational milestones are achieved and, in certain cases, then vest only if the recipient remains with the company for an extended period of time.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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