X0306 4 2017-12-31 0 0000897448 AMARIN CORP PLC\UK AMRN 0001199637 THERO JOHN F C/O AMARIN PHARMA, INC. 1430 ROUTE 206 BEDMINSTER NJ 07921 1 1 0 0 President and CEO Ordinary Shares 2017-12-31 4 M 0 37500 A 1172503 D Ordinary Shares 2017-12-31 4 F 0 15732 4.01 D 1156771 D Restricted Stock Units 0.00 2017-12-31 4 M 0 37500 0.00 D Ordinary Shares 37500 225000 D The Ordinary Shares may be represented by American Depositary Shares, each of which represents one Ordinary Share. As previously reported on July 8, 2015, the Reporting Person was granted 600,000 Restricted Stock Units ("RSUs") under the Amarin Corporation plc 2011 Stock Incentive Plan (the "Plan"). These RSUs vest in 16 equal quarterly installments. The tenth vesting event occurred on December 31, 2017. Not applicable. Please see the section titled "Remarks" below for additional information. Represents a 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. Each RSU represents a contingent right to receive one Ordinary Share or cash in lieu thereof at the Issuer's discretion. In the event of a Change of Control (as defined in the Plan), the grant described in this Form 4 vests in full. As of the date of this Form 4, the Reporting Person owns or holds the right to acquire an aggregate of 9,572,112 Ordinary Shares of the Issuer in the form of Ordinary Shares, stock options and Restricted Stock Units granted under the Amarin Corporation plc 2002 Stock Option Plan and the Plan /s/ John F. Thero 2018-01-02