Equity	6 Months Ended
Jun. 30, 2021
Equity [Abstract]
Equity	(6) Equity Preferred Stock In March 2015, the Company entered into subscription agreements with both existing and new investors, or the Purchasers, for the private placement of a total of 391,017,970 restricted American Depositary Shares, or ADSs, each representing one share of Amarin’s Series A Convertible Preference Shares, par value £0.05 per share, in the capital of the Company, or Series A Preference Shares. For each restricted ADS, the Purchasers paid a negotiated price of $0.15 (equating to $1.50 on an as-if-converted-to-ordinary-shares basis), resulting in gross proceeds to the Company of approximately $58.6 million before deducting estimated offering expenses of approximately $0.7 million. At the request of the holders and provided certain conditions were met, each ten Series A Preference Shares were able to be consolidated and redesignated as one ordinary share, par value £0.50 per share, in the capital of the Company, each ordinary share to be represented by ADSs. During the years ended December 31, 2020, 2018, and 2015, the Company issued 28,931,746, 3,886,718, and 6,283,333 ADSs, respectively, upon consolidation and redesignation of Series A Preference Shares at the request of the holders, such that no Series A Preference Shares remained outstanding as of June 30, 2021 and December 31, 2020. Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 for a more complete background. Common Stock During the six months ended June 30, 2021 and 2020, in addition to ordinary shares issued as described in Preferred Stock above and in Incentive Equity Awards below, the Company issued 226,402 and 123,608 ordinary shares, respectively, under the Amarin Corporation plc 2017 Employee Stock Purchase Plan. Incentive Equity Awards As of June 30, 2021, there were an aggregate of 19,666,637 stock options and 10,413,802 restricted stock units, or RSUs, outstanding, representing approximately 5% and 2%, respectively, of outstanding shares on a fully diluted basis. During the six months ended June 30, 2021 and 2020, the Company issued 810,459 and 560,755 common shares, respectively, as a result of the exercise of stock options, resulting in gross and net proceeds of $2.1 million during the six months ended June 30, 2021 and $1.7 million during the six months ended June 30, 2020. During the six months ended June 30, 2021 and 2020, the Company issued 1,031,171 and 1,143,934 common shares, respectively, related to the vesting of RSUs, of which 398,214 and 418,847 shares, respectively, were retained as treasury shares as settlement of employee tax obligations. During the six months ended June 30, 2021 and 2020, in connection with the achievement of certain regulatory and sales performance conditions associated with the REDUCE-IT clinical trial and subsequent revenue growth, the Company issued 1,762,244 and 974,754 common shares, respectively, upon vesting of performance-based RSUs granted in 2017 and 2018, of which 747,955 and 411,956 shares, respectively, were retained as treasury shares as settlement of employee tax obligations. These performance-based RSUs will continue to vest ratably monthly through the end of August 2021. On June 14, 2021, the Company granted a total of 218,000 RSUs and 278,271 stock options to members of the Company’s Board of Directors under the Amarin Corporation plc 2020 Stock Incentive Plan, or the 2020 Plan. The RSUs vest in equal installments over a three-year period upon the earlier of the anniversary of the grant date or the Company’s annual general meeting of shareholders in such anniversary year, and are subject to deferred settlement upon the Director’s separation of service with the Company. The stock options vest in full upon the earlier of the one-year anniversary of the grant date or the Company’s annual general meeting of shareholders in such anniversary year. Upon termination of service to the Company or upon a change of control, each director shall be entitled to a payment equal to the fair market value of one share of Amarin common stock per award vested or granted, respectively, which is required to be made in shares. On January 4, 2021, the Company granted a total of 3,265,700 RSUs and 3,100,200 stock options to employees under the 2020 Plan. The RSUs vest annually over a three-year period and the stock options vest quarterly over a four-year period with a one-year cliff vesting. Also on January 4, 2021, the Company granted a total of 1,345,800 RSUs to certain employees under the 2020 Plan that vest upon the achievement of specified operational performance conditions. On June 1, 2020, the Company granted a total of 782,520 RSUs to employees under the Amarin Corporation plc 2011 Stock Incentive Plan, or the 2011 Plan. The RSUs vest quarterly over a three-year period. On March 2, 2020 and February 3, 2020, the Company granted a total of 821,950 RSUs and 1,875,000 stock options, respectively, to employees under the 2011 Plan. The RSUs vest annually over a three-year period and the stock options vest quarterly over a four-year period. Also on February 3, 2020, the Company granted a total of 1,253,400 RSUs to employees under the 2011 Plan that vest upon the achievement of specified sales performance conditions.

Equity

6 Months Ended

Jun. 30, 2021

(6) Equity

Preferred Stock

In March 2015, the Company entered into subscription agreements with both existing and new investors, or the Purchasers, for the private placement of a total of 391,017,970 restricted American Depositary Shares, or ADSs, each representing one share of Amarin’s Series A Convertible Preference Shares, par value £0.05 per share, in the capital of the Company, or Series A Preference Shares. For each restricted ADS, the Purchasers paid a negotiated price of $0.15 (equating to $1.50 on an as-if-converted-to-ordinary-shares basis), resulting in gross proceeds to the Company of approximately $58.6 million before deducting estimated offering expenses of approximately $0.7 million. At the request of the holders and provided certain conditions were met, each ten Series A Preference Shares were able to be consolidated and redesignated as one ordinary share, par value £0.50 per share, in the capital of the Company, each ordinary share to be represented by ADSs. During the years ended December 31, 2020, 2018, and 2015, the Company issued 28,931,746, 3,886,718, and 6,283,333 ADSs, respectively, upon consolidation and redesignation of Series A Preference Shares at the request of the holders, such that no Series A Preference Shares remained outstanding as of June 30, 2021 and December 31, 2020. Refer to the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 for a more complete background.

Common Stock

During the six months ended June 30, 2021 and 2020, in addition to ordinary shares issued as described in Preferred Stock above and in Incentive Equity Awards below, the Company issued 226,402 and 123,608 ordinary shares, respectively, under the Amarin Corporation plc 2017 Employee Stock Purchase Plan.

Incentive Equity Awards

As of June 30, 2021, there were an aggregate of 19,666,637 stock options and 10,413,802 restricted stock units, or RSUs, outstanding, representing approximately 5% and 2%, respectively, of outstanding shares on a fully diluted basis.

During the six months ended June 30, 2021 and 2020, the Company issued 810,459 and 560,755 common shares, respectively, as a result of the exercise of stock options, resulting in gross and net proceeds of $2.1 million during the six months ended June 30, 2021 and $1.7 million during the six months ended June 30, 2020. During the six months ended June 30, 2021 and 2020, the Company issued 1,031,171 and 1,143,934 common shares, respectively, related to the vesting of RSUs, of which 398,214 and 418,847 shares, respectively, were retained as treasury shares as settlement of employee tax obligations. During the six months ended June 30, 2021 and 2020, in connection with the achievement of certain regulatory and sales performance conditions associated with the REDUCE-IT clinical trial and subsequent revenue growth, the Company issued 1,762,244 and 974,754 common shares, respectively, upon vesting of performance-based RSUs granted in 2017 and 2018, of which 747,955 and 411,956 shares, respectively, were retained as treasury shares as settlement of employee tax obligations. These performance-based RSUs will continue to vest ratably monthly through the end of August 2021.

On June 14, 2021, the Company granted a total of 218,000 RSUs and 278,271 stock options to members of the Company’s Board of Directors under the Amarin Corporation plc 2020 Stock Incentive Plan, or the 2020 Plan. The RSUs vest in equal installments over a three-year period upon the earlier of the anniversary of the grant date or the Company’s annual general meeting of shareholders in such anniversary year, and are subject to deferred settlement upon the Director’s separation of service with the Company. The stock options vest in full upon the earlier of the one-year anniversary of the grant date or the Company’s annual general meeting of shareholders in such anniversary year. Upon termination of service to the Company or upon a change of control, each director shall be entitled to a payment equal to the fair market value of one share of Amarin common stock per award vested or granted, respectively, which is required to be made in shares.

On January 4, 2021, the Company granted a total of 3,265,700 RSUs and 3,100,200 stock options to employees under the 2020 Plan. The RSUs vest annually over a three-year period and the stock options vest quarterly over a four-year period with a one-year cliff vesting. Also on January 4, 2021, the Company granted a total of 1,345,800 RSUs to certain employees under the 2020 Plan that vest upon the achievement of specified operational performance conditions.

On June 1, 2020, the Company granted a total of 782,520 RSUs to employees under the Amarin Corporation plc 2011 Stock Incentive Plan, or the 2011 Plan. The RSUs vest quarterly over a three-year period.

On March 2, 2020 and February 3, 2020, the Company granted a total of 821,950 RSUs and 1,875,000 stock options, respectively, to employees under the 2011 Plan. The RSUs vest annually over a three-year period and the stock options vest quarterly over a four-year

period. Also on February 3, 2020, the Company granted a total of 1,253,400 RSUs to employees under the 2011 Plan that vest upon the achievement of specified sales performance conditions.