Amarin (AMRN) 10-K 1 Mar 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Feb. 24, 2023	Jun. 30, 2022
Document And Entity Information [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Trading Symbol	AMRN
Entity Registrant Name	AMARIN CORP PLC\UK
Entity Central Index Key	0000897448
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false
Entity Public Float			$ 721.2
Entity File Number	0-21392
Entity Incorporation, State or Country Code	X0
Entity Address, Address Line One	Iconic Offices, The Greenway
Entity Tax Identification Number	00-0000000
Entity Address, Address Line Two	Block C Ardilaun Court
Entity Address, Address Line Three	112-114 St Stephens Green
Entity Address, City or Town	Dublin
Entity Address, Postal Zip Code	2
Entity Address, Country	IE
City Area Code	353 (0) 1
Local Phone Number	6699 020
Document Annual Report	true
Document Transition Report	false
Title of each class	American Depositary Shares (ADS(s)), each ADSrepresenting the right to receive one (1) Ordinary Share ofAmarin Corporation plc
Name of each exchange on which registered	NASDAQ
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Certain information required to be disclosed in Part III of this Annual Report on Form 10-K is incorporated by reference from the registrant’s definitive proxy statement to be filed not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K.
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Iselin, New Jersey
American Depositary Shares
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		385,785,809
Ordinary Shares
Document And Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		20,329,912

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current Assets:
Cash and cash equivalents	$ 217,666	$ 219,454
Restricted cash	523	3,918
Short-term investments	91,695	234,674
Accounts receivable, net	130,990	163,653
Inventory	228,732	234,676
Prepaid and other current assets	19,492	22,352
Total current assets	689,098	878,727
Property, plant and equipment, net	874	1,425
Long-term investments	1,275	34,996
Long-term inventory	163,620	121,254
Operating lease right-of-use asset	9,074	7,660
Other long-term assets	458	456
Intangible asset, net	21,780	23,547
TOTAL ASSETS	886,179	1,068,065
Current Liabilities:
Accounts payable	64,602	114,922
Accrued expenses and other current liabilities	192,678	253,111
Current deferred revenue	2,199	2,649
Total current liabilities	259,479	370,682
Long-Term Liabilities:
Long-term deferred revenue	13,147	14,060
Long-term operating lease liability	10,015	8,576
Other long-term liabilities	8,205	7,648
Total liabilities	290,846	400,966
Commitments and contingencies (Note 7)
Stockholders’ Equity:
Common stock, GBP 0.50 par, unlimited authorized; 412,333,087 shares issued, 404,346,256 shares outstanding at December 31, 2022; 404,084,775 shares issued, 396,598,008 shares outstanding at December 31, 2021	299,002	294,027
Additional paid-in capital	1,885,352	1,855,246
Treasury stock; 7,986,831 shares at December 31, 2022; 7,486,767 shares at December 31, 2021	(61,770)	(60,726)
Accumulated deficit	(1,527,251)	(1,421,448)
Total stockholders’ equity	595,333	667,099
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 886,179	$ 1,068,065

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - £ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value	£ 0.50	£ 0.50
Common stock, shares authorized, unlimited	Unlimited	Unlimited
Common stock, issued	412,333,087	404,084,775
Common stock, outstanding	404,346,256	396,598,008
Treasury stock, shares	7,986,831	7,486,767

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Total revenue, net	$ 369,193	$ 583,187	$ 614,060
Less: Cost of goods sold	108,631	121,327	131,444
Less: Cost of goods sold - restructuring inventory	18,078
Gross margin	242,484	461,860	482,616
Operating expenses:
Selling, general and administrative	304,416	408,334	463,312
Research and development	30,411	29,307	38,959
Restructuring	13,526	13,717
Total operating expenses	348,353	451,358	502,271
Operating (loss) income	(105,869)	10,502	(19,655)
Interest income	2,819	1,220	4,901
Interest expense	(15)	(129)	(2,605)
Other (expense) income, net	(740)	(302)	104
(Loss) income from operations before taxes	(103,805)	11,291	(17,255)
Provision for income taxes	(1,998)	(3,562)	(745)
Net (loss) income	$ (105,803)	$ 7,729	$ (18,000)
(Loss) earnings per share:
Basic	$ (0.26)	$ 0.02	$ (0.05)
Diluted	$ (0.26)	$ 0.02	$ (0.05)
Weighted average shares outstanding:
Basic	401,155	395,992	381,759
Diluted	401,155	402,480	381,759
Product Revenue, Net
Total revenue, net	$ 366,511	$ 580,320	$ 607,025
Licensing and Royalty Revenue
Total revenue, net	$ 2,682	$ 2,867	$ 7,035

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Shares	Common Shares	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2019	$ 608,263	$ 21,850	$ 269,173	$ (35,900)	$ 1,764,317	$ (1,411,177)
Balance (in shares) at Dec. 31, 2019		289,317,460	365,014,893
Balance, Treasury Shares (in shares) at Dec. 31, 2019				(4,910,992)
Conversion of Series A Convertible Preferred Stock, net	(504)	$ (21,850)	$ 18,020		3,326
Conversion of Series A Convertible Preferred Stock, net (in shares)		(289,317,460)	28,931,746
Issuance of common stock under employee stock purchase plan	1,957		$ 225		1,732
Issuance of common stock under employee stock purchase plan (in shares)			347,153
Exercise of stock options	5,158		$ 1,062		4,096
Exercise of stock options (in shares)			1,623,460
Vesting of restricted stock units	(15,182)		$ 1,635	$ (15,182)	(1,635)
Vesting of restricted stock units (in shares)			2,507,748	(975,927)
Stock-based compensation	45,813				45,813
Income (loss) for the period	(18,000)					(18,000)
Balance at Dec. 31, 2020	627,505		$ 290,115	$ (51,082)	1,817,649	(1,429,177)
Balance (in shares) at Dec. 31, 2020			398,425,000
Balance, Treasury Shares (in shares) at Dec. 31, 2020				(5,886,919)
Issuance of common stock under employee stock purchase plan	1,650		$ 275		1,375
Issuance of common stock under employee stock purchase plan (in shares)			399,286
Exercise of stock options	$ 2,921		$ 827		2,094
Exercise of stock options (in shares)	1,203,845		1,203,845
Vesting of restricted stock units	$ (9,644)		$ 2,810	$ (9,644)	(2,810)
Vesting of restricted stock units (in shares)			4,056,644	(1,599,848)
Stock-based compensation	36,938				36,938
Income (loss) for the period	7,729					7,729
Balance at Dec. 31, 2021	$ 667,099		$ 294,027	$ (60,726)	1,855,246	(1,421,448)
Balance (in shares) at Dec. 31, 2021			404,084,775
Balance, Treasury Shares (in shares) at Dec. 31, 2021	7,486,767			(7,486,767)
Issuance of common stock under employee stock purchase plan	$ 605		$ 283		322
Issuance of common stock under employee stock purchase plan (in shares)			456,696
Issuance of common stock for milestone payment	8,203		$ 3,461		4,742
Issuance of common stock for milestone payment (in shares)			5,817,942
Exercise of stock options	$ 60		$ 21		39
Exercise of stock options (in shares)	33,303		33,303
Vesting of restricted stock units	$ (1,044)		$ 1,210	$ (1,044)	(1,210)
Vesting of restricted stock units (in shares)			1,940,371	(500,064)
Stock-based compensation	26,213				26,213
Income (loss) for the period	(105,803)					(105,803)
Balance at Dec. 31, 2022	$ 595,333		$ 299,002	$ (61,770)	$ 1,885,352	$ (1,527,251)
Balance (in shares) at Dec. 31, 2022			412,333,087
Balance, Treasury Shares (in shares) at Dec. 31, 2022	7,986,831			(7,986,831)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net (loss) income	$ (105,803)	$ 7,729	$ (18,000)
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Depreciation and amortization	551	587	597
Amortization of investments	473	1,929	1,602
Stock-based compensation	26,213	36,938	45,813
Amortization of debt discount and debt issuance costs			635
Amortization of intangible asset	2,545	2,270	1,441
Changes in assets and liabilities:
Accounts receivable, net	32,663	(9,079)	(38,144)
Inventory	(36,422)	(167,066)	(112,095)
Prepaid and other current assets	2,860	8,595	(17,636)
Other long-term assets	(2)	(24)	642
Interest receivable	341	738	(1,329)
Accrued interest payable			(428)
Deferred revenue	(1,363)	(1,923)	(2,214)
Accounts payable, accrued expenses and other current liabilities	(102,729)	51,516	114,741
Other long-term liabilities	581	1,253	2,629
Net cash used in operating activities	(180,092)	(66,537)	(21,746)
CASH FLOWS FROM INVESTING ACTIVITIES:
Sale and maturities of securities	257,520	394,294	301,989
Purchases of securities	(81,633)	(290,195)	(678,700)
Investment in website development costs	(599)
Disposal (purchases) of furniture, fixtures and equipment		4	(252)
Net cash provided by (used in) investing activities	175,288	104,103	(376,963)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock under employee stock purchase plan	605	1,650	1,957
Proceeds from exercise of stock options, net of transaction costs	60	2,921	5,158
Payment of transaction costs for conversion of preferred stock			(504)
Payment on debt from royalty-bearing instrument			(50,336)
Taxes related to stock-based awards	(1,044)	(9,644)	(15,182)
Net cash used in financing activities	(379)	(5,073)	(58,907)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS AND RESTRICTED CASH	(5,183)	32,493	(457,616)
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, BEGINNING OF PERIOD	223,372	190,879	648,495
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH, END OF PERIOD	218,189	223,372	190,879
Cash (paid) received during the year for:
Interest			(2,043)
Income taxes	(1,782)	3,656	(207)
Supplemental disclosure of non-cash transactions:
Laxdale milestone		$ 12,000
Shares issued in settlement of Laxdale milestone payment	8,203
Initial recognition of operating lease right-of-use asset	$ 2,041
Conversion of Series A Convertible Preferred Stock into common stock			$ 18,020

Nature of Business and Basis of

Nature of Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Nature of Business and Basis of Presentation	(1) Nature of Business and Basis of Presentation Nature of Business Amarin Corporation plc, or Amarin, or the Company, is a pharmaceutical company focused on the commercialization and development of therapeutics to improve cardiovascular, or CV, health and reduce CV risk. Most of the Company’s historical revenue and sales, marketing and administrative activities and costs have been associated with commercial operations in the United States, or U.S. The Company has launched commercial operations in certain European countries, such as the United Kingdom, or the UK, and continues pre-launch commercial activities throughout the rest of Europe. The Company’s operations outside of the U.S. and Europe are in early stages of development with reliance on third-party commercial partners in select geographies. The Company’s commercialized product, VASCEPA ® (icosapent ethyl), was approved by the U.S. Food and Drug Administration, or U.S. FDA, in July 2012 for use as an adjunct to diet to reduce triglyceride, or TG, levels in adult patients with severe ( > 500 mg/dL) hypertriglyceridemia, or the MARINE indication. VASCEPA was also approved for another indication in December 2019 for use as an adjunct to maximally tolerated statin therapy for reducing persistent cardiovascular risk in select high risk patients, or the REDUCE-IT indication. In 2020, following our unsuccessful appeals of a court ruling in favor of two generic drug companies, Dr. Reddy's Laboratories, Inc., or Dr. Reddy's, and Hikma Pharmaceuticals USA Inc., or Hikma, and certain of their affiliates, or collectively, the Defendants, several of the Company's patents covering the MARINE indication were declared as invalid. As a result, the following generic versions of VASCEPA have obtained U.S. FDA approval with labeling consistent with the MARINE indication of VASCEPA and have entered the U.S. market with a 1-gram capsule: Company FDA MARINE Indication Approval Launch Date Hikma Pharmaceuticals USA Inc. May 2020 November 2020 Dr. Reddy’s Laboratories, Inc. August 2020 June 2021 Teva Pharmaceuticals USA, Inc. September 2020 September 2022 (1) Apotex, Inc. June 2021 January 2022 (1) - Teva launched a 0.5-gram capsule in September 2022 and a 1-gram capsule in January 2023. On March 26, 2021, the European Commission, or EC, approved the marketing authorization application for VAZKEPA, hereinafter along with the U.S. brand name VASCEPA, collectively referred to as VASCEPA, in the European Union, or EU, to reduce the risk of cardiovascular events in high-risk, statin-treated adult patients who have elevated triglycerides ( > 150 mg/dL) and either established cardiovascular disease or diabetes and at least one additional cardiovascular risk event. On April 22, 2021, the Company announced that the Medicines and Healthcare Products Regulatory Agency, or MHRA, approved VAZKEPA in England, Scotland and Wales to reduce cardiovascular risk through MHRA’s new ‘reliance’ route. On December 7, 2022, the Company announced that Swissmedic approved VAZKEPA in Switzerland. Collectively CHMP, EMA, EC and MHRA are referred to herein as the European Regulatory Authorities. In November 2020, the Company announced topline results from the Phase 3 clinical trial of VASCEPA conducted by the Company’s partner in China. On February 9, 2021, the Company announced that regulatory review processes for approval of VASCEPA in Mainland China and Hong Kong had commenced. The Chinese National Medical Products Administration, or NMPA, has accepted for review the new drug application for VASCEPA based on the results from the Phase 3 clinical trial and the results from the Company’s prior studies of VASCEPA. On February 23, 2022, the Hong Kong Department of Health concluded their evaluation and approved the use of VASCEPA under the REDUCE-IT indication. The Company currently has strategic collaborations to develop and commercialize VASCEPA in select territories outside the United States. Amarin is responsible for supplying VASCEPA to all markets in which the product is sold, including the United States, and certain countries throughout Europe, as well as, in Canada, Lebanon and the United Arab Emirates where the drug is promoted and sold via collaboration with third-party companies that compensate Amarin for such supply. Amarin is not responsible for providing any generic company with drug product. The Company operates in one business segment. Basis of Presentation The consolidated financial statements included herein have been prepared by the Company in accordance with accounting principles generally accepted in the United States and pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC. The consolidated financial statements reflect all adjustments of a normal and recurring nature that, in the opinion of management, are necessary to present fairly the Company’s financial position, results of operations and cash flows for the periods indicated. The preparation of the Company’s consolidated financial statements in conformity with U.S. Generally Accepted Accounting Principles, or GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. The results of operations for the years ended December 31, 2022, 2021 and 2020 are not necessarily indicative of the results for any future period. Certain numbers presented throughout this document may not add precisely to the totals provided due to rounding. Absolute and percentage changes are calculated using the underlying amounts in thousands. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. The accompanying consolidated financial statements of the Company and subsidiaries have been prepared on a basis which assumes that the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business, as well as the ongoing global pandemic, COVID-19. At December 31, 2022, the Company had Total assets of $ 886.2 million, of which $ 310.6 million consisted of cash and liquid short-term and long-term investments. More specifically, the Company had Current assets of $ 689.1 million, including Cash and cash equivalents of $ 217.7 million, Short-term investments of $ 91.7 million, Accounts receivable, net, of $ 131.0 million and Inventory of $ 228.7 million. In addition, at December 31, 2022, the Company had Long-term investments of $ 1.3 million and Long-term inventory of $ 163.6 million. At December 31, 2022 , the Company had no debt outstanding.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Significant Accounting Policies	(2) Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates Accounting estimates are based on historical experience and other factors that are considered reasonable under the circumstances. Estimates and assumptions relied upon in preparing these consolidated financial statements relate to, but are not limited to, such items as provisions for sales returns, rebates and incentives, chargebacks, and other sales allowances; depreciable/amortizable lives; asset impairments; valuation allowance on deferred taxes; probabilities of achievement of performance conditions for certain equity awards; amounts recorded for licensing revenue; contingencies and accruals. Because of the uncertainties inherent in such estimates, actual results may differ from these estimates. Management periodically evaluates estimates used in the preparation of the consolidated financial statements for continued reasonableness. Use of Forecasted Financial Information in Accounting Estimates The use of forecasted financial information is inherent in many of the Company’s accounting estimates including, but not limited to, determining the estimated fair values of intangible assets, evaluating the need for valuation allowances for deferred tax assets, and assessing the Company’s ability to continue as a going concern. Such forecasted financial information is comprised of numerous assumptions regarding the Company’s future revenues, cash flows, and operational results. Management believes that its financial forecasts are reasonable and appropriate based upon current facts and circumstances. Because of the inherent nature of forecasts, however, actual results may differ from these forecasts. Management regularly reviews the information related to these forecasts and adjusts the carrying amounts of the applicable assets prospectively, if and when actual results differ from previous estimates. Revenue Recognition In accordance with Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers , or Topic 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services committed within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For a complete discussion of accounting for net product revenue and licensing revenue, see Note 13—Revenue Recognition. Distribution Costs The Company records distribution costs related to shipping product to its customers, primarily through the use of common carriers or external distribution services, in Cost of goods sold. Cash and Cash Equivalents and Restricted Cash Cash and cash equivalents consist of cash, deposits with banks and short-term highly liquid money market instruments with original maturities at the date of purchase of 90 days or less. Restricted cash represents cash and cash equivalents pledged to guarantee repayment of certain expenses which may be incurred for business travel under corporate credit cards held by employees. Accounts Receivable, net Accounts receivable, net, comprised of trade receivables, are generally due within 45 days and are stated at amounts due from customers. The Company recognizes an allowance for losses on accounts receivable in an amount equal to the estimated probable losses net of any recoveries. The allowance is based primarily on assessment of specific identifiable customer accounts considered at risk or uncollectible, as well as an analysis of current receivables aging and expected future write-offs. The expense associated with the allowance for doubtful accounts is recognized as Selling, general, and administrative expense. The Company has not historically experienced any significant credit losses. All customer accounts are actively managed and no losses in excess of amounts reserved are currently expected; however, the Company is monitoring the potential negative impact of COVID-19 on the Company’s customers’ ability to meet their financial obligations. The following table summarizes the impact of accounts receivable reserves on the gross trade accounts receivable balances at December 31, 2022 and 2021: In thousands December 31, 2022 December 31, 2021 Gross trade accounts receivable $ 187,418 $ 262,948 Trade allowances ( 44,626 ) ( 86,636 ) Chargebacks ( 11,802 ) ( 11,714 ) Allowance for doubtful accounts — ( 945 ) Accounts receivable, net $ 130,990 $ 163,653 Inventory The Company states inventories at the lower of cost or net realizable value. Cost is determined based on actual cost using the average cost method. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company classifies inventory as long-term inventory when consumption of the finished goods and work in process inventory is expected beyond the normal operating cycle. The Company classifies finished goods expected to be consumed within a normal operating cycle and all of VASCEPA's active pharmaceutical ingredient, or API, as current inventory. An allowance is established when management determines that certain inventories may not be saleable. If inventory cost exceeds expected net realizable value due to obsolescence, damage or quantities in excess of expected demand, changes in price levels or other causes, the Company will reduce the carrying value of such inventory to net realizable value and recognize the difference as a component of cost of goods sold in the period in which it occurs. The Company capitalizes inventory purchases of saleable product from approved suppliers while inventory purchases from suppliers prior to regulatory approval are included as a component of research and development expense. The Company expenses inventory identified for use as marketing samples when they are packaged. The average cost reflects the actual purchase price of VASCEPA API. Long-Lived Asset Impairment The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of these assets is determined by comparing the forecasted undiscounted net cash flows of the operation to which the assets relate to their carrying amount. If impairment is indicated, the assets are written down to fair value. Fair value is determined based on discounted forecasted cash flows or appraised values, depending on the nature of the assets. Intangible Asset, net Intangible asset, net consists of website development costs and milestone payments to the former shareholders of Laxdale Limited, or Laxdale, related to the 2004 acquisition of the rights to VASCEPA, which is the result of VASCEPA receiving marketing approval in the U.S. for the first indication in 2012, the expanded label in 2019 and marketing authorization in Europe in 2021. These assets are amortized over its estimated useful life on a straight-line basis. See Note 7—Commitments and Contingencies for further information regarding other obligations related to the acquisition of Laxdale. Costs for Patent Litigation and Legal Proceedings Costs for patent litigation or other legal proceedings are expensed as incurred and included in Selling, general and administrative expense. Research and Development Costs The Company charges research and development costs to operations as incurred. Research and development expenses are comprised of costs incurred by the Company in performing research and development activities, including: salary and benefits; stock-based compensation expense; laboratory supplies and other direct expenses; contractual services, including clinical trial and pharmaceutical development costs; commercial supply investment in its drug candidates; and infrastructure costs, including facilities costs and depreciation expense. In addition, research and development costs include the costs of product supply received from suppliers when such receipt by the Company is prior to regulatory approval of the supplier, as well as license fees related to the Company’s strategic collaboration with Mochida Pharmaceutical Co., Ltd., or Mochida. Selling, General and Administrative Costs The Company charges selling, general and administrative costs to operations as incurred. Selling, general and administrative costs include salaries and benefits, stock-based compensation expense, and costs of programs and infrastructure necessary for the general conduct of the Company’s business, including those incurred as a result of the commercialization of VASCEPA in the United States. Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts and tax bases of assets and liabilities and operating loss carryforwards and other tax attributes using enacted rates expected to be in effect when those differences reverse. Valuation allowances are provided against deferred tax assets that are not more likely than not to be realized. Deferred tax assets and liabilities are classified as non-current in the consolidated balance sheet. The Company provides reserves for potential payments of tax to various tax authorities and does not recognize tax benefits related to uncertain tax positions and other issues. Tax benefits for uncertain tax positions are based on a determination of whether a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized, assuming that the matter in question will be decided based on its technical merits. The Company’s policy is to record interest and penalties in the provision for income taxes, as applicable. The Company regularly assesses its ability to realize deferred tax assets. Changes in historical earnings performance, future earnings projections, and changes in tax laws, among other factors, may cause the Company to adjust its valuation allowance on deferred tax assets, which would impact the Company’s income tax expense in the period in which it is determined that these factors have changed. Excess tax benefits and deficiencies that arise upon vesting or exercise of share-based payments are recognized as an income tax benefit and expense, respectively, in the consolidated statement of operations. Excess income tax benefits are classified as cash flows from operating activities and cash paid to taxing authorities arising from the withholding of shares from employees are classified as cash flows from financing activities. The Company’s and its subsidiaries’ income tax returns are periodically examined by various tax authorities, including the Internal Revenue Service, or IRS, and states. The Company is currently under audit by the IRS for the Company’s 2018 U.S. income tax return and by the New Jersey Department of Treasury for the years 2012 to 2015 . Although the outcome of tax audits is always uncertain and could result in significant cash tax payments, the Company does not believe the outcome of these audits will have a material adverse effect on its consolidated financial position or results of operations. (Loss) Earnings per Share Basic net (loss) earnings per share is determined by dividing net (loss) income by the weighted average shares of common stock outstanding during the period. Diluted net (loss) earnings per share is determined by dividing net (loss) income by diluted weighted average shares outstanding. Diluted weighted average shares reflects the dilutive effect, if any, of potentially dilutive common shares, such as from the exercise of stock options and vesting of restricted stock units calculated using the treasury stock method. In periods with reported net operating losses, all stock options and restricted stock units outstanding are deemed anti-dilutive such that basic and diluted net loss per share are equal. The calculation of net (loss) income and the number of shares used to compute basic and diluted net (loss) earnings per share for the years ended December 31, 2022, 2021, and 2020 are as follows: In thousands 2022 2021 2020 Net (loss) income —basic and diluted $ ( 105,803 ) $ 7,729 $ ( 18,000 ) Weighted average shares outstanding—basic 401,155 395,992 381,759 Effect of dilutive securities: Stock options — 4,420 — Restricted stock and restricted stock units — 2,068 — Weighted average shares outstanding—diluted 401,155 402,480 381,759 Net (loss) earnings per share—basic $ ( 0.26 ) $ 0.02 $ ( 0.05 ) Net (loss) earnings per share—diluted $ ( 0.26 ) $ 0.02 $ ( 0.05 ) For the years ended December 31, 2022, 2021 and 2020, the following potentially dilutive securities were not included in the computation of net (loss) earnings per share because the effect would be anti-dilutive or because performance criteria were not yet met for awards contingent upon such measures: In thousands 2022 2021 2020 Stock options 19,182 9,926 16,664 Restricted stock and restricted stock units 14,461 3,764 7,710 Laxdale milestone shares — 1,984 — Stock options are anti-dilutive during periods of net earnings when the exercise price of the stock options exceeds the market price of the underlying shares on the last day of the reporting period. Restricted stock and restricted stock units are anti-dilutive during periods of net earnings when underlying performance-based vesting requirements were not achieved as of the last day of the reporting period. Stock-Based Compensation The Company accounts for stock-based compensation in accordance with the guidance of FASB ASC Topic 718, Compensation-Stock Compensation , or ASC 718, and requires the fair value of all stock-based payments to employees and non-employees to be recognized in the consolidated statement of operations over the requisite service period. The fair value of the Company's restricted stock units is determined to be the market price on the date of the grant. The Company estimates the fair value of stock option awards on the date of the grant using the Black-Scholes Model, which requires that the Company makes certain assumptions regarding: (i) the expected volatility in the market price of its common stock; (ii) dividend yield; (iii) risk-free interest rates; and (iv) the period of time employees are expected to hold the award prior to exercise, referred to as the expected holding period. As a result, if the Company revises its assumptions and estimates, stock-based compensation expense could change materially for future grants. For awards with performance conditions, if the achievement of the performance conditions is deemed probable, the Company recognizes compensation expense based on the grant date fair value of the award over the requisite service period. The Company reassesses the probability of achievement of the performance conditions each reporting period. The Company estimates the level of forfeitures expected to occur based on its historical data and records compensation cost only for those awards that are ultimately expected to vest. See Note 9—Stock Incentive Plans and Stock-Based Compensation for further discussion. Concentration of Credit Risk Financial instruments that potentially subject the Company to credit risk consist primarily of cash and cash equivalents, short-term and long-term investments, and accounts receivable. The Company maintains substantially all of its cash and cash equivalents and short-term and long-term investments, in financial institutions believed to be of high-credit quality. A significant portion of the Company’s sales are to wholesalers in the pharmaceutical industry. The Company monitors the creditworthiness of customers to whom it grants credit terms and has not experienced any credit losses. The Company does not require collateral or any other security to support credit sales. Three customers individually accounted for 10% or more of the Company’s gross product sales. Customers A, B, and C accounted for 35 % , 31 % , and 27 % , respectively, of gross product sales for the year ended December 31, 2022 and represented 35 % , 21 % , and 39 % , respectively, of the gross accounts receivable balance as of December 31, 2022. Customers A, B, and C accounted for 37 % , 28 % and 27 % , respectively, of gross product sales for the year ended December 31, 2021 and represented 39 % , 22 % , and 35 % , respectively, of the gross accounts receivable balance as of December 31, 2021 . The Company has not experienced any significant write-offs of its accounts receivable. All customer accounts are actively managed and no losses are currently expected; however, the Company is monitoring the potential negative impact of COVID-19 on the Company’s customers’ ability to meet their financial obligations. Concentration of Suppliers The Company has contractual freedom to source the API for VASCEPA and to procure other services supporting its supply chain and has entered into supply agreements with multiple suppliers. The Company’s supply of product for commercial sale and clinical trials is dependent upon relationships with third-party manufacturers and suppliers. The Company cannot provide assurance that its efforts to procure uninterrupted supply of VASCEPA to meet market demand will continue to be successful or that it will be able to renew current supply agreements on favorable terms or at all. Significant alteration to or disruption or termination of the Company’s current supply chain, including as a result of COVID-19, or the Company’s failure to enter into new and similar agreements in a timely fashion, if needed, could have a material adverse effect on its business, condition (financial and other), prospects or results of operations. The Company currently has manufacturing agreements with multiple independent API manufacturers and several independent API encapsulators and packagers for VASCEPA manufacturing. Each of these API manufacturers, encapsulators and packagers is U.S. FDA-approved and certain of these API manufacturers, encapsulators and packagers are also approved by the European Regulatory Authorities for manufacturing VAZKEPA in Europe. These suppliers are also used by the Company to source supply to meet the clinical trial and commercial demands of its partners in other countries. Each of these suppliers has qualified and validated its manufacturing processes. There can be no guarantee that these or other suppliers with which the Company may contract in the future to manufacture VASCEPA or VASCEPA API will remain qualified to do so to its specifications or that these and any future suppliers will have the manufacturing capacity to meet potential global demand for VASCEPA. Foreign Currency Monetary assets and liabilities denominated in a foreign currency are remeasured into U.S. dollars at period-end exchange rates. Gains and losses from the remeasurement are included in Other (expense) income, net in the consolidated statements of operations. For transactions settled during the applicable period, gains and losses are included in Other (expense) income, net in the consolidated statements of operations. Certain amounts payable pursuant to supply contracts are denominated in currencies other than the U.S. dollar. The Company recorded a foreign currency loss within the Other (expense) income, net on the consolidated statement of operations of $ 0.7 million, $ 0.6 million and less than $ 0.1 million for each of the years ended December 31, 2022, 2021, and 2020 , respectively. Fair Value of Financial Instruments The Company provides disclosure of financial assets and financial liabilities that are carried at fair value based on the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements may be classified based on the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities using the following three levels: Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.) and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). Level 3—Unobservable inputs that reflect the Company’s estimates of the assumptions that market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available, including its own data. The following tables present information about the estimated fair value of the Company’s assets and liabilities as of December 31, 2022 and 2021 and indicate the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value: December 31, 2022 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 81,870 $ 81,870 $ — $ — U.S. Treasury Shares 3,117 3,117 — — Agency Securities 1,554 1,554 — — Corporate Bonds 28,416 — 28,416 — Commercial Paper 62,347 — 62,347 — Repo Securities 3,250 — 3,250 — Asset Backed Securities 1,260 — 1,260 — Certificate of Deposit 9,100 — 9,100 — Non-US Government 1,393 — 1,393 — Total $ 192,307 $ 86,541 $ 105,766 $ — December 31, 2021 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 95,063 $ 95,063 $ — $ — U.S. Treasury Shares 23,219 23,219 — — Corporate Bonds 83,587 — 83,587 — Commercial Paper 121,773 — 121,773 — Repo Securities 8,000 — 8,000 — Asset Backed Securities 8,816 — 8,816 — Certificate of Deposit 21,553 — 21,553 — Non-US Government 12,900 — 12,900 — Total $ 374,911 $ 118,282 $ 256,629 $ — The carrying amount of the Company’s cash and cash equivalents approximates fair value because of their short-term nature. The cash and cash equivalents consist of cash, deposits with banks and short-term highly liquid money market instruments with remaining maturities at the date of the purchase of 90 days or less. The Company’s held-to-maturity investments are stated at amortized cost, which approximates fair value. The Company does not intend to sell these investment securities and the contractual maturities are not greater than 24 months . Those with original maturities greater than 90 days and less than 12 months are included in short-term investments on its consolidated balance sheet. Those with remaining maturities in excess of 12 months are included in long-term investments on its consolidated balance sheet. Unrealized gains or losses on held-to-maturity securities are not recognized until maturity, except other-than-temporary unrealized losses which are recognized in earnings in the period incurred. The Company evaluates securities with unrealized losses to determine whether such losses are other than temporary. The unrealized gain or loss for the year ended December 31, 2022 and December 31, 2021 were losses of $ 0.4 million and $ 0.2 million, respectively. Interest on investments is reported in interest income. The carrying amounts of accounts payable and accrued liabilities approximate fair value because of their short-term nature. Segment and Geographical Information Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated on a regular basis by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources to an individual segment and in assessing performance of the segment. The Company currently operates in one business segment, which is the development and commercialization of VASCEPA. A single management team that reports to the Company’s chief decision-maker, who is the Chief Executive Officer, comprehensively manages the business. Accordingly, the Company does not have separately reportable segments. Restructuring On September 22, 2021, the Company announced a Go-to-Market strategy for VASCEPA. As part of this strategy, the Company completed a reduction of its U.S. field force to approximately 300 sales representatives, enhanced managed care access and optimized VASCEPA prescriptions for cardiovascular risk reduction. During the year ended December 31, 2021, the Company recognized approximately $ 13.7 million in charges related to the reduction in force, substantially all of which were cash expenditures for one-time termination benefits and associated costs. On June 6, 2022, the Company announced a Comprehensive Cost Reduction Plan which included an organizational restructuring plan to address shifts within the Company’s U.S. business. As part of the plan, the Company completed a reduction of its U.S. field force from approximately 300 sales representatives to approximately 75 sales representatives. During the year ended December 31, 2022 the Company recognized approximately $ 9.4 million within Restructuring expense on the consolidated statement of operations related to the Comprehensive Cost Reduction Plan, substantially all of which are cash expenditures. The Company also reviewed its contractual supplier purchase obligations and has taken steps to amend supplier agreements to align supply arrangements with current and future market demand resulting in charges of $ 18.1 million recognized within Cost of goods sold - restructuring inventory for the year ended December 31, 2022 on the consolidated statement of operations. The Company continues to negotiate with other contract suppliers to align its supply arrangements with current and future global demand which may result in additional costs to the Company. On August 19, 2022, the Company announced that after the conclusion of the fourth and final round of negotiations with the National Association of Statutory Health Insurance Funds, or GKV-SV, a viable agreement on the reimbursement price of VAZKEPA in Germany could not be reached. As a result of the negotiation outcome with the GKV-SV, the Company discontinued its German business operations effective September 1, 2022. The Company recognized approximately $ 4.2 million within Restructuring expense on the consolidated statement of operations, substantially all of which are cash expenditures. The following table sets forth the components of the Company's restructuring charges for the years ended December 31, 2022 and 2021 (none in 2020): For the Year Ended December 31, In thousands 2022 2021 Employee restructuring separation charges $ 9,310 $ 13,717 Vendor contract charges 4,216 — Total restructuring expense 13,526 13,717 Restructuring inventory 18,078 — Stock forfeitures 591 — Total restructuring costs incurred $ 32,195 $ 13,717 The following table shows the change in restructuring liability which is included within accrued expenses and other current liabilities: In thousands Restructuring Liability Balance at December 31, 2021 $ 1,186 Costs incurred 32,195 Payments ( 33,189 ) Balance at December 31, 2022 $ 192 Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, and are early adopted by the Company or adopted as of the specified effective date. The Company has evaluated all recently issued accounting pronouncements through the date of the financial statements and found that no recently issued accounting pronouncements, when adopted, will have a material impact on the Company’s condensed consolidated financial position, results of operations, and cash flows, or do not apply to the Company’s operations.

Intangible Asset

Intangible Asset	12 Months Ended
	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Asset	(3) Intangible Asset Intangible asset consists of website development costs and milestone payments to the former shareholders of Laxdale related to the 2004 acquisition of the rights to VASCEPA, which is the result of VASCEPA receiving marketing approval in the U.S. for the first indication in 2012, the expanded label in 2019 and marketing approval in Europe in 2021. For the year ended December 31, 2022 , the Company capitalized $ 0.8 million of costs associated with the development of a global company website. In accordance with ASC 350, the Company evaluates the remaining useful life of the intangible asset at each reporting period to determine if any events or circumstances warrant a revision to the remaining period of amortization. As of December 31, 2022, the intangible assets have an estimated weighted-average remaining useful life of 8.1 years. The carrying value as of December 31, 2022 and 2021 is as follows: In thousands December 31, 2022 December 31, 2021 Technology rights $ 32,859 $ 32,081 Accumulated amortization ( 11,079 ) ( 8,534 ) Intangible asset, net $ 21,780 $ 23,547 Amortization expense for the years ended December 31, 2022 and 2021 was $ 2.5 million and $ 2.3 million, respectively. Estimated future amortization expense, based upon the Company’s intangible asset, as of December 31, 2022 is as follows: In thousands Year Ending December 31, Amount 2023 $ 2,805 2024 2,805 2025 2,805 2026 2,546 2027 2,546 Thereafter 8,273 Total $ 21,780

Inventory

Inventory	12 Months Ended
	Dec. 31, 2022
Inventory Disclosure [Abstract]
Inventory	(4) Inventory The Company capitalizes its purchases of saleable inventory of VASCEPA from suppliers that have been qualified by the U.S. FDA and other global regulatory agencies. Inventories as of December 31, 2022 and 2021 consist of the following: In thousands December 31, 2022 December 31, 2021 Raw materials $ 126,391 $ 107,695 Work in process 52,297 41,965 Finished goods 213,664 206,270 Inventory $ 392,352 $ 355,930 The Company classifies inventory as long-term when consumption of the finished goods and work in process inventory are expected beyond the normal operating cycle. As of December 31, 2022 and 2021, we had $ 163.6 million and $ 121.3 million of Long-term inventory, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	(5) Property, Plant and Equipment Property, plant and equipment as of December 31, 2022 and 2021 consist of the following: In thousands Useful Life (in years) December 31, 2022 December 31, 2021 Furniture and fixtures 5 $ 1,633 $ 1,633 Leasehold improvements lesser of useful life or lease term 869 869 Software 3 - 5 617 617 Computer equipment 3 - 5 227 227 Property, plant and equipment 3,346 3,346 Accumulated depreciation and amortization ( 2,472 ) ( 1,921 ) Property, plant and equipment, net $ 874 $ 1,425 The Company provides for depreciation and amortization using the straight-line method by charges to operations in amounts that depreciate the cost of the fixed asset over its estimated useful life. Depreciation expense for the years ended December 31, 2022, 2021, and 2020 were $ 0.6 million, annually. Upon retirement or sale of assets, the cost of the assets disposed and the related accumulated depreciation are removed from the consolidated balance sheet and any resulting gain or loss is credited or expensed to operations. Repairs and maintenance costs are expensed as incurred.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	(6) Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following as of December 31, 2022 and 2021: In thousands December 31, 2022 December 31, 2021 Payroll and payroll-related expenses $ 20,302 $ 19,730 Sales and marketing accruals 1,672 3,563 Accrued revenue allowances 135,061 184,216 All other 35,643 45,602 Accrued expenses and other current liabilities $ 192,678 $ 253,111

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	(7) Commitments and Contingencies Litigation – U.S. ANDAs On March 30, 2020, the Nevada Court, ruled in favor of two generics companies, Hikma and Dr. Reddy’s, in Amarin’s patent litigation related to its ANDAs that sought U.S. FDA approval for sale of generic versions of VASCEPA for the original indication of VASCEPA as an adjunct to diet to reduce TG levels in adult patients with severe (>500 mg/dL) hypertriglyceridemia. On September 3, 2020, the U.S. Court of Appeals for the Federal Circuit, or the Federal Circuit, upheld the March ruling by the Nevada Court in favor of the two generics companies. On October 2, 2020, the Company filed a combined petition for panel rehearing or rehearing en banc. On November 4, 2020, the Company’s rehearing and en banc petitions were denied. On February 11, 2021, Amarin filed a petition for a writ of certiorari with the United States Supreme Court to ask the Court to hear the Company’s appeal in this litigation, which was denied on June 18, 2021. On May 22, 2020 and August 10, 2020, Hikma and Dr. Reddy’s, respectively, received U.S. FDA approval to market its generic versions of VASCEPA. During the ANDA litigation, the Company reached agreements with Teva and Apotex, under which they received royalty-free license agreements to promote a generic version of icosapent ethyl in the U.S. under certain circumstances, one of which circumstances was achieved when the Federal Circuit upheld the ruling by the Nevada Court and Hikma launched its generic version of icosapent ethyl. On September 11, 2020, and June 30, 2021, Teva and Apotex, respectively, received U.S. FDA approval to market their respective generic versions of icosapent ethyl. In November 2020, Hikma announced the price and launched its generic version of icosapent ethyl. In June 2021, Dr. Reddy’s announced the price and launched its generic version of icosapent ethyl. In January 2022, Apotex announced the price and launched its generic version of icosapent ethyl. In September 2022, Teva announced the price and launched its generic version of icosapent ethyl for the 0.5-gram capsule and the 1.0 gram capsule in January 2023. All generic versions of icosapent ethyl as approved by the U.S. FDA pertains to the MARINE indication of VASCEPA, lowering of TG levels in patients with very high TG (>500 mg/dL). Current generic competition, together with past and on-going litigation related to such generic versions of icosapent ethyl are applicable to the U.S. only. The Company did not seek, nor is VAZKEPA approved in Europe for lowering of TG levels in patients with very high TG (>500 mg/dL). The active pharmaceutical ingredient in VASCEPA is difficult and time consuming to manufacture, often requires considerable advanced planning and long-term financial commitment, including to manufacturing infrastructure such as dedicated facilities, to ensure sufficient capacity is available when needed. The Company has invested over a decade of resources and expenses to develop with individual members of its third-party, active pharmaceutical ingredient supply chain the technical knowhow, manufacturing processes and related regulatory approvals that have helped enable the Company’s suppliers to supply the Company’s need for clinical and commercial supply globally. In November 2020, the Company filed a patent infringement lawsuit against Hikma in the United States District Court in Delaware. The complaint alleged that Hikma induced the infringement of VASCEPA-related CV risk reduction U.S. Patent Nos. 9,700,537 (Composition for preventing the occurrence of cardiovascular event in multiple risk patient), 8,642,077 (Stable pharmaceutical composition and methods of using same), and 10,568,861 (Methods of reducing the risk of a cardiovascular event in a subject at risk for cardiovascular disease) by making, selling, offering to sell and importing generic icosapent ethyl capsules in or into the United States. In January 2021, the Company expanded the scope of the VASCEPA CV risk reduction patent infringement lawsuit against Hikma to include a health care insurance provider in the United States, Health Net LLC, or Health Net. Through insurance coverage and economic incentives the Company alleged that Health Net has actively induced pharmacies to dispense, and patients to use, Hikma generic icosapent ethyl capsules in infringement of the related patents. In the complaint, the Company sought remedies including a permanent injunction against the unlawful inducement by Hikma and Health Net of infringing uses of the Hikma generic product, i.e., uses to reduce cardiovascular risk as detailed in the patents, and monetary damages in an amount sufficient to compensate the Company for such infringement. On January 4, 2022, the district court hearing the case granted Hikma's motion to dismiss. On October 13, 2022, the district court granted final judgement on the aspect of the litigation relating to the Company and Hikma. The Company has appealed the decision of the district court. On December 26, 2022, the Company entered into a settlement agreement with Health Net that resolved the litigation relating to the Company and Health Net. The Company will continue to consider its legal options against parties similarly situated to Health Net and Hikma and acting in concert with either by making or selling any drug product or component thereof covered by the subject patents, or inducing others to do the same. As has been a practice in the generic pharmaceutical industry, on April 27, 2021 and February 21, 2023, Dr. Reddy’s and Hikma, respectively, filed a complaint against the Company in the United States District Court for the District of New Jersey, Civil actions No.21-cv-10309 and No.3:23-cv-01016, alleging various antitrust violations stemming from alleged anticompetitive practices related to the supply of active pharmaceutical ingredient of VASCEPA. The complaints also includes a related state law tortious interference claim. Damages sought include recovery for alleged economic harm to Dr. Reddy’s and Hikma's, payors and consumers, treble damages and other costs and fees. Injunctive relief against the alleged violative activities is also being sought by Dr. Reddy’s and Hikma. Amarin believes it has valid defenses and will vigorously defend against the claims. In March 2021, Amarin received a civil investigative demand, or CID, from the U.S. Federal Trade Commission and a subpoena from the New York Attorney General with respect to information on the same antitrust topic covered in the Dr. Reddy's litigation. Similarly, in June 2020, the Company received a CID from the U.S. Department of Justice, or the DOJ, informing Amarin that the DOJ is investigating whether aspects of its promotional speaker programs and copayment waiver program during the period from January 1, 2015 to the present violated the U.S. Anti-Kickback Statute and the U.S. Civil False Claims Act, in relation to the sale and marketing of VASCEPA by the Company and its previous co-marketing partner, Kowa Pharmaceuticals America, Inc. The Company believes such contact from the governments may have been prompted by a generic competitor. The inquiries require the Company to produce documents and answer written questions, or interrogatories, relevant to specified time periods. Amarin is cooperating with the government agencies and cannot predict when these investigations will be resolved, the outcome of the investigations or their potential impact on the Company’s business. As has been a practice of class action legal counsel following governmental investigations and litigation by generics companies, Amarin is also named as a defendant in six antitrust class action lawsuits in the District Court for the District of New Jersey. Amarin is a defendant in a class action lawsuit filed by Uniformed Fire Officers Association Family Protection Plan Local 854 and the Uniformed Fire Officers Association for Retired Fire Officers Family Protection Plan, on behalf of indirect purchasers, in the District Court for the District of New Jersey, Civil Action No. 21-12061, alleging Amarin and its co-defendant suppliers violated state and federal antitrust laws by monopolizing and engaging in a conspiracy to restrain trade in the icosapent ethyl drug and API markets. Amarin is a defendant in a class action lawsuit filed by The International Union of Operating Engineers Locals 137, 137A, 137B, 137C, 137R, on behalf of indirect purchasers, in the District Court for the District of New Jersey, Civil Action No. 21-12416, alleging Amarin violated state and federal antitrust laws by monopolizing and engaging in a conspiracy to restrain trade in the icosapent ethyl drug and API markets. Amarin is a defendant in a class action lawsuit filed by Local 464A United Food and Commercial Workers Union Welfare Service Benefit Fund, on behalf of direct purchasers, in the District Court for the District of New Jersey, Civil Action No. 21-13009. Amarin is a defendant in a class action lawsuit filed by Teamsters Health & Welfare Fund of Philadelphia and Vicinity, on behalf of indirect purchasers, in the District Court for the District of New Jersey, Civil Action No. 21-13406, alleging Amarin violated state and federal antitrust laws by monopolizing and engaging in a conspiracy to restrain trade in the icosapent ethyl drug and API markets. Amarin is a defendant in a class action lawsuit filed by Board of Trustees of Heavy and General Laborers' Local Unions 472 and 172 of N.J. Welfare Fund, on behalf of indirect purchasers, in the District Court of New Jersey, Civil Action No. 21-14639, alleging Amarin violated state and federal antitrust laws by monopolizing and engaging in a conspiracy to restrain trade in the icosapent ethyl drug and API markets. These cases have been consolidated into In re Vascepa Antitrust Litigation (Indirect Purchasers), Civil Action No. 21-12061, in the District Court for the District of New Jersey. Amarin is a defendant in a class action lawsuit filed by KPH Healthcare Services, Inc., on behalf of direct purchasers, in the District Court for the District of New Jersey, Civil Action No. 21-12747, alleging Amarin violated state and federal antitrust laws by monopolizing and engaging in a conspiracy to restrain trade in the icosapent ethyl drug and API markets. This case has been coordinated with the consolidated indirect purchaser case above as In re Vascepa Antitrust Litigation (Direct Purchasers), Civil Action No. 21-12747, in the District Court for the District of New Jersey. Such antitrust litigation and investigations can be lengthy, costly and could materially affect and disrupt the Company’s business. The Company cannot predict when these matters will be resolved, their outcome or their potential impact on the Company’s business. If a government determines that Amarin has violated antitrust law, the Company could be subject to significant civil fines and penalties. The Company intends to vigorously enforce its intellectual property rights relating to VASCEPA, but cannot predict the outcome of these lawsuits or any subsequently filed lawsuits. Litigation – Other On February 22, 2019, a purported investor in the Company’s publicly traded securities filed a putative class action lawsuit against Amarin Corporation plc, the former chief executive officer and chief scientific officer in the U.S. District Court for the District of New Jersey, Debendra Sharma v. Amarin Corporation plc, John F. Thero and Steven Ketchum, No. 2:19-cv-06601 (D.N.J. Feb. 22, 2019). On March 12, 2019, another purported investor filed a substantially similar lawsuit captioned Richard Borghesi v. Amarin Corporation plc, John F. Thero and Steven Ketchum, No. 3:19-cv-08423 (D.N.J. March 12, 2019). On May 14, 2019 the court consolidated the cases under the caption In re Amarin Corporation PLC Securities Litigation, No. 3:19-cv-06601 and appointed two other purported shareholders, Dan Kotecki and the Gaetano Cecchini Living Trust, as Co-Lead Plaintiffs. Co-Lead Plaintiffs filed a consolidated amended complaint, or Amended Complaint, on July 22, 2019 that added as defendants the Company’s former chief medical officer and the Company’s former chief executive officer. The Amended Complaint alleged that from September 24, 2018 to November 9, 2018 the Company misled investors by releasing topline results for the REDUCE-IT study without disclosing data on biomarker increases in the placebo group as compared with baseline measurement. The Amended Complaint alleged that these data suggest that the mineral oil placebo used in the REDUCE-IT study may have interfered with statin absorption in the placebo group, which they alleged may have increased adverse outcomes in the placebo group. The Amended Complaint further alleged that these purported misrepresentations and omissions inflated the share price. Based on these allegations, the suit asserted claims under the Securities Exchange Act of 1934 and sought unspecified monetary damages and attorneys’ fees and costs. On March 29, 2021, the court granted the Company’s motion to dismiss this litigation for failure to state a valid claim. The litigation was dismissed without prejudice, giving the plaintiffs the right to file an amended complaint. Plaintiffs in this action did not file an amended complaint within the permitted filing deadline. Plaintiffs filed a notice of appeal of the motion to dismiss ruling, which has been denominated In re: Amarin Corp. PLC , case number 21-2071 (3d Cir.). On June 14, 2022, the Court of Appeals for the Third Circuit affirmed the dismissal of the matter by the trial district court. On October 21, 2021, a purported investor in the Company's publicly traded securities filed a putative class action lawsuit against Amarin Corporation plc, the former chief executive officer and the former chief financial officer in the U.S. District Court for the District of New Jersey, Vincent Dang v. Amarin Corporation plc, John F. Thero and Michael W. Kalb, No. 1:21-cv-19212 (D.N.J. Oct. 21, 2021) and a subsequent case, Dorfman v. Amarin Corporation plc, et al., No. 3:21-cv-19911 (D.N.J. filed Nov. 10, 2021), was filed in November 2021. In December 2021, several Amarin shareholders moved to consolidate the cases, or the Securities Litigation, and appoint a lead plaintiff and lead counsel pursuant to the Private Securities Litigation Reform Act. The plaintiffs filed an amended complaint on January 13, 2023 that added as a defendant the Company's former general counsel. The complaints in these actions are nearly identical and allege that the Company misled investors by allegedly downplaying the risk associated with the ANDA litigation described above and the risk that certain of the Company's patents would be invalidated. Based on these allegations, plaintiff alleges that he purchased securities at an inflated share price and brings claims under the Securities and Exchange Act of 1934 seeking unspecified monetary damages and attorneys' fees and costs. The Company believes it has valid defenses and will vigorously defend against the claims but cannot predict the outcome. The Company is unable to reasonably estimate the loss exposure, if any, associated with these claims. On April 7, 2022, a purported investor in the Company's publicly traded securities filed a derivative lawsuit naming the same officer defendants from the Securities Litigation, the Officer Defendants, and also the members of the Company's board of directors, and the Company as nominal defendant in the U.S. District Court for the District of New Jersey, Gary Schader v. Amarin Corporation plc, John F. Thero, Michael W. Kalb, Lars G. Ekman, Jan Van Heek, Karim Mikhail, Patrick J. O'Sullivan, Per Wold-Olsen, Kristine Peterson, David Stack, and Joseph S. Zakrzewski, No. 3:22-cv-02017 (D.N.J. Apr. 7, 2022). The complaint alleges, like the Securities Litigation, that the defendants allegedly downplayed the risk associated with the ANDA litigation and the risk that certain of the Company's patents would be invalidated. Based on the allegations, plaintiffs allege that the directors breached their fiduciary duties and that the Officer Defendants were unjustly enriched, and plaintiffs seek contribution from the Officer Defendants for any liability they incur in the Securities Litigation and for which they are indemnified by the Company. On July 1, 2022, the plaintiff voluntarily dismissed this matter. In addition to the above, in the ordinary course of business, the Company is from time to time involved in lawsuits, claims, investigations, proceedings, and threats of litigation relating to intellectual property, commercial arrangements and other matters. Milestone and Supply Purchase Obligations The Company currently has long-term supply agreements with multiple API suppliers and encapsulators. The Company is relying on these suppliers to meet current and potential future global demand for VASCEPA. Certain supply agreements require annual minimum volume commitments by the Company and certain volume shortfalls may require payments for such shortfalls. These agreements include requirements for the suppliers to meet certain product specifications and qualify their materials and facilities with applicable regulatory authorities including the U.S. FDA. The Company has incurred certain costs associated with the qualification of product produced by these suppliers. On June 6, 2022, the Company announced a Comprehensive Cost Reduction Plan which includes a comprehensive cost and organizational restructuring plan to address current shifts within the Company’s U.S. business as a result of the generic competition. As part of this plan, the Company has reviewed its contractual supplier purchase obligations and has entered into agreements with some suppliers to amend supplier agreements to align supply arrangements with current and future market demand. The Company continues to negotiate with other contract suppliers to align its supply arrangements with current and future global demand which may result in additional costs to the Company. As of December 31, 2022 , the Company has a total of approximately $ 86.0 million in future contractual purchase obligations without consideration to ongoing discussions with other suppliers. On March 26, 2021, the EC approved the marketing authorization application for VAZKEPA. Under the 2004 share repurchase agreement with Laxdale upon receipt of pricing approval in Europe for the first indication for VASCEPA (or first indication of any product containing intellectual property acquired from Laxdale in 2004), the Company was obligated to make an aggregate stock or cash payment to the former shareholders of Laxdale (at the sole option of each of such former shareholders) of £ 7.5 million. On July 13, 2022 in connection with the United Kingdom's National Institute for Health and Care Excellence, or NICE's, final guidance for reimbursement of VAZKEPA and use across the National Health Service, or NHS, in England and Wales, representing receipt of marketing approval in Europe for the first indication for VAZKEPA, the Company became obligated to make the aggregate milestone payment of £ 7.5 million to Laxdale’s former shareholders (in either stock or cash at the election of each shareholder). A s of December 31, 2022, the Company has settled the first European indication approval milestone through issuance of stock and cash payments based on the respective shareholder's election. Also under the Laxdale agreement, upon receipt of a marketing approval in Europe for a further indication of VASCEPA (or further indication of any other product acquired from Laxdale in 2004), the Company must make an aggregate stock or cash payment (at the sole option of each of such former shareholder) of £ 5.0 million (approximately $ 6.0 million as of December 31, 2022) for the potential market approval. The Company has no provision for any of these obligations, except as noted above, since the amounts are either not paid or payable as of December 31, 2022 .

Equity

Equity	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Equity	(8) Equity Common Stock On July 13, 2022, in connection with the United Kingdom's National Institute for Health and Care Excellence, or NICE's, final guidance for reimbursement of VAZKEPA and use across the National Health Service, or NHS, in England and Wales, representing receipt of marketing approval in Europe for the first indication for VAZKEPA, the Company became obligated to make an aggregate milestone payment of £ 7.5 million to Laxdale's former shareholders (in either stock or cash at the election of each shareholder) under the 2004 purchase agreement among the Company and such former shareholders. One of the shareholders elected to receive payment in stock for its pro rata portion of the milestone payment, resulting in the issuance of 5,817,942 shares at a price of $ 1.41 per share in July 2022. During the years ended December 31, 2022 and 2021, other than as described elsewhere in this Annual Report on Form 10-K, including in the Notes to Consolidated Financial Statements, the Company did not engage in any transactions involving its common stock. Refer to Incentive Equity Awards below for discussion of ordinary shares issued as a result of stock option exercises and the vesting of restricted stock units. Refer to Note 9—Stock Incentive Plans and Stock Based Compensation for discussion of shares issued under the Company’s employee stock purchase plan. Incentive Equity Awards The Company issues incentive equity awards, including incentive and non-qualified stock options and restricted stock units, under the Amarin Corporation plc 2020 Stock Incentive Plan, or the 2020 Plan, which is the successor to the Amarin Corporation plc 2011 Stock Incentive Plan, as amended, or the 2011 Plan, and the Amarin Corporation plc 2002 Stock Option Plan, as amended, or the 2002 Plan, and together with the 2020 Plan and 2011 Plan, the Plans. Refer to Note 9—Stock Incentive Plans and Stock Based Compensation for further information regarding the Company’s incentive equity plans and awards. The following table summarizes the aggregate number of stock options and restricted stock units, or RSUs, outstanding under the 2020 Plan as of December 31, 2022: December 31, 2022 Outstanding stock options 19,182,111 % of outstanding shares on a fully diluted basis 4 % Outstanding RSUs 14,461,050 % of outstanding shares on a fully diluted basis 3 % The following table represents equity awards activity during the years ended December 31, 2022 and 2021: For the Year Ended December 31, 2022 2021 Common shares issued for stock option exercises 33,303 1,203,845 Gross and net proceeds from stock option exercises $ 59,686 $ 2,921,000 Common shares issued in settlement of vested RSUs 1,940,371 1,203,845 Shares retained for settlement of employee tax obligations ─ RSUs 500,064 782,917 Common shares issued in settlement of vested Performance-Based RSUs (1) — 1,923,316 Shares retained for settlement of employee tax obligations ─ Performance-Based RSUs — 816,931 (1) Performance-based RSUs vested in connection with the achievement of certain regulatory and sales performance conditions associated with the REDUCE-IT clinical trial and subsequent revenue growth. These performance-based RSUs have fully vested as of August 2021. During the years ended December 31, 2022 and 2021, the Company granted a total of 3,065,000 and 4,535,117 stock options, respectively, and 9,069,500 and 5,497,700 RSUs, respectively, to employees under the Plans. The RSUs typically vest annually over a three - or four-year period and the stock options typically vest quarterly over a four-year period. Also during 2022 and 2021, the Company granted a total of 1,919,500 and 2,008,800 RSUs, respectively, to employees under the Plans that vest upon the achievement of specified performance conditions. In addition, during the years ended December 31, 2022 and 2021, the Company granted a total of 1,973,124 and 278,271 stock options, respectively, and 1,597,955 and 218,000 RSUs, respectively, to members of the Company’s Board of Directors under the Plans. 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. 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.

Stock Incentive Plans and Stock

Stock Incentive Plans and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Stock Incentive Plans and Stock-Based Compensation	(9) Stock Incentive Plans and Stock-Based Compensation On March 16, 2020, the Company’s Board of Directors, upon the recommendation of the Remuneration Committee, adopted, subject to shareholder approval, the 2020 Plan which was subsequently approved by the Company’s shareholders on July 13, 2020 at the Annual General Meeting of Shareholders. The 2020 Plan is the successor to the Company’s 2011 Plan, which was set to expire on July 12, 2021, and the Company’s 2002 Plan, the Plans. The 2020 Plan allows the Company to grant stock options, both incentive and non-qualified options, to employees and Directors, restricted stock units to employees and unrestricted shares to Directors. The maximum number of the Company’s Ordinary Shares of £ 0.50 each or any ADS’s, as to be issued under the 2020 Plan shall not exceed the sum of (i) 20,000,000 shares and (ii) the number of Shares that remained available for grants under the Company’s 2011 Plan as of July 13, 2020. If any award granted and outstanding under the Plans expires or is forfeited, surrendered, canceled or otherwise terminated, the shares may be made available for subsequent grants under the 2020 Plan. The 2020 Plan is administered by the Remuneration Committee of the Company’s Board of Directors and expires on July 13, 2030. Stock Options Under the terms of the Plans, stock options typically vest over a four-year period and expire after a ten-year term. The stock options are granted at an exercise price equal to the closing price of the Company’s American Depositary Shares on the grant date. The following table summarizes all stock option activity for the year ended December 31, 2022: In thousands (except per share amounts and years) Number of Weighted Weighted Aggregate Outstanding as of January 1, 2022 18,493 $ 7.32 Granted 5,038 2.56 Forfeited ( 4,105 ) 8.39 Expired ( 211 ) 11.65 Exercised ( 33 ) 1.79 Outstanding as of December 31, 2022 19,182 5.80 6.2 years $ 158 Exercisable as of December 31, 2022 12,888 6.80 4.9 years $ 86 Vested and expected to vest as of December 31, 2022 18,867 5.83 6.2 years $ 155 Available for future grant as of December 31, 2022 15,383 The weighted average grant date fair value of stock options granted during the years ended December 31, 2022, 2021, and 2020 was $ 2.56 , $ 5.12 , and $ 14.43 , respectively. The total grant date fair value of options vested during the years ended December 31, 2022, 2021, and 2020 was $ 16.6 million, $ 21.1 million, and $ 22.5 million, respectively. During the years ended December 31, 2022, 2021 and 2020, the Company received proceeds from the exercise of options of $ 0.1 million, $ 2.9 million, and $ 5.2 million, respectively. The total intrinsic value of options exercised during the years ended December 31, 2022, 2021, and 2020 was nominal, $ 4.9 million, and $ 9.0 million, respectively, calculated as the difference between the quoted stock price of the Company’s common stock as of the reporting date and the exercise prices of the underlying awards. As of December 31, 2022, options have $ 13.5 million of unrecognized stock-based compensation expense with such expense expected to be recognized over a weighted-average period of approximately 2.1 years. The fair value of stock options on the date of grant was estimated using the Black-Scholes option pricing model. Use of a valuation model requires management to make certain assumptions with respect to selected model inputs, which include: • Risk free rate : The risk-free interest rate is based on zero-coupon U.S. Treasury securities with a maturity term approximating the expected life of the option at the date of grant. • Expected dividend yield : No dividend yield has been assumed as the Company does not currently pay dividends on its common stock and does not anticipate doing so in the foreseeable future. • Expected option life: The expected life was determined using the simplified method based on the term and vesting period. • Expected volatility: Expected stock price volatility was calculated based on the historical volatility of the Company’s common stock over the expected life of the option. For 2022, 2021, and 2020, the Company used the following assumptions to estimate the fair value of share-based payment awards: 2022 2021 2020 Risk-free interest rate 1.64 % - 4.35 % 0.53 % - 1.36 % 0.33 % - 1.74 % Expected dividend yield 0.00 % 0.00 % 0.00 % Expected option life (years) 6.25 6.25 6.25 Expected volatility 96 % - 101 % 96 % - 99 % 84 % - 99 % Employee stock options generally require future service and vest ratably over a four-year service period and are settled by the issuance of new common shares. The grant date fair value of the stock options, net of an estimated forfeiture rate is amortized straight-line over the awards’ vesting periods or respective requisite service periods and is adjusted for actual forfeitures over such period. The Company recorded compensation expense in relation to stock options of $ 14.8 million, $ 23.0 million, and $ 22.4 million for the years ended December 31, 2022, 2021, and 2020, respectively. Restricted Stock Units The restricted stock units vest based upon either a time-based service condition, a performance condition, or both. The grant date fair value of the restricted stock unites, net of the estimated forfeiture rate, is amortized straight-line over the vesting periods or requisite service periods and is adjusted for actual forfeitures over such period. For any awards with a performance condition, the probability that any performance criteria will be achieved is assessed by management and compensation expense for such awards is only recorded to the extent that the attainment of the performance criteria is deemed to be probable. The following table presents the restricted stock unit activity for the year ended December 31, 2022 : In thousands (except per share amounts) Shares Weighted Average Outstanding as of January 1, 2022 9,277 7.70 Granted 12,587 2.97 Vested ( 1,940 ) 7.30 Forfeited ( 5,463 ) 6.79 Outstanding as of December 31, 2022 14,461 $ 3.98 The Company recorded compensation expense in relation to restricted stock units of $ 11.4 million, $ 13.9 million, and $ 23.4 million for the years ended December 31, 2022, 2021, and 2020 respectively. As of December 31, 2022, restricted stock units have $ 23.7 million of unrecognized stock-based compensation expense with such expense to be recognized over a weighted-average period of approximately 2.2 years. The following table presents the stock-based compensation expense related to stock-based awards for the years ended December 31, 2022, 2021, and 2020: In thousands 2022 2021 2020 Research and development $ 4,465 $ 4,327 $ 6,568 Selling, general and administrative 22,339 32,305 39,245 Restructuring ( 591 ) 306 — Stock-based compensation expense $ 26,213 $ 36,938 $ 45,813 Employee Stock Purchase Plan On March 13, 2017, the Board adopted, subject to shareholder approval, the Amarin Corporation plc 2017 Employee Stock Purchase Plan, or the ESPP, which was approved by the Company’s shareholders on May 15, 2017. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the Internal Revenue Code. The maximum fair market value of stock which can be purchased by a participant in a calendar year is $ 25,000 . Under the ESPP, an aggregate of 3,000,000 ordinary shares (each ordinary share to be represented by one ADS) are reserved and available for issuance, which were registered with the SEC on August 2, 2017, for sale to eligible employees. Subject to certain exclusions, any employee of the Company’s U.S. subsidiary, Amarin Pharma, Inc., who works at least 20 hours per week and has been employed for at least six months as of the first day of the applicable offering period is eligible to participate in the ESPP. Eligible employees may authorize payroll deductions of up to 15 percent of their base pay to be withheld to purchase ordinary shares, subject to terms and limitations of the plan, at a price equal to 85 percent of the lower of the fair market values of the Company’s ordinary shares as of the beginning or the end of six-month offering periods. For the offering periods ended on the last business day on or before each of May 31, 2022 and November 30, 2022, the Company issued 265,214 shares and 191,482 shares, respectively, at a purchase price of $ 1.45 per share and $ 1.15 per share, respectively. For the offering periods ended on the last business day on or before each of May 31, 2021 and November 30, 2021, the Company issued 226,402 shares and 172,884 shares, respectively, at a purchase price of $ 3.86 per share and $ 3.06 per share, respectively. For the offering periods ended on the last business day on or before each of May 31, 2020 and November 30, 2020, the Company issued shares 123,608 shares and 223,545 shares, respectively, at a purchase price of $ 5.83 per share and $ 4.22 per share, respectively. As of December 31, 2022, 1,361,577 shares were reserved for future issuance under the ESPP.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	(10) Income Taxes The Company recognizes interest and penalties related to uncertain tax positions within the provision for income taxes. The total amount of unrecognized tax benefits that would affect the Company’s effective tax rate if recognized is $ 8.2 million and $ 7.9 million as of December 31, 2022 and 2021, respectively. The Company recognized interest related to uncertain tax positions of $ 0.5 million and $ 0.9 million for the years ended December 31, 2022 and 2021 , respectively. No penalties have been recognized in conjunction with these positions. The following is a reconciliation of the total amounts of unrecognized tax benefits for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Beginning uncertain tax benefits $ 22,040 $ 24,034 $ 26,743 Prior year—increases — 16 2,428 Prior year—decreases ( 9,107 ) ( 2,248 ) ( 5,391 ) Current year—increases 5,782 238 254 Ending uncertain tax benefits $ 18,715 $ 22,040 $ 24,034 The Company files income tax returns in the United States, Ireland and United Kingdom, or UK. The Company remains subject to tax examinations in the following jurisdictions as of December 31, 2022: Jurisdiction Tax Years United States—Federal 2018 - 2022 United States—State 2012 - 2022 Ireland 2018 - 2022 United Kingdom 2021 - 2022 The Company does no t expect any gross liabilities to expire in 2023 based on statutory lapses or audits. The components of income (loss) from operations before taxes were as follows for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 United States $ 5,358 $ 10,222 $ 14,915 Ireland and United Kingdom ( 112,527 ) ( 4,368 ) ( 32,170 ) Other 3,364 5,437 — Total (loss) / income before taxes $ ( 103,805 ) $ 11,291 $ ( 17,255 ) The provision for income taxes shown in the accompanying consolidated statements of operations consists of the following for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Current: United States—Federal $ 562 $ 2,690 $ 45 United States—State 573 716 700 Foreign 863 156 — Total current $ 1,998 $ 3,562 $ 745 Deferred: United States—Federal ( 3,721 ) 5,222 1,972 United States—State 284 ( 3,057 ) 1,956 Foreign ( 1,646 ) ( 1,619 ) ( 26,793 ) Change in valuation allowance 5,083 ( 546 ) 22,865 Total deferred $ — $ — $ — Provision for income taxes $ 1,998 $ 3,562 $ 745 The provision for income taxes differs from the amount computed by applying the statutory income tax rate to income before taxes due to the following for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Benefits from taxes at statutory rate $ ( 25,952 ) $ 2,823 $ ( 4,314 ) Rate differential 9,141 ( 4,416 ) 128 Change in valuation reserves 5,083 ( 546 ) 22,865 Nondeductible employee compensation 2,344 5,249 6,122 Stock option/RSU windfall (shortfall) 3,569 81 ( 3,262 ) ISO disqualifying disposition windfall — ( 219 ) ( 253 ) Research and development credits ( 958 ) ( 1,170 ) ( 6,225 ) Tax return to provision adjustments 424 ( 8,372 ) ( 138 ) Net operating loss carryback — — ( 2,465 ) Foreign exchange 7,859 4,109 ( 10,852 ) Permanent and other ( 1,542 ) 863 ( 4,283 ) Uncertain tax positions ( 3,290 ) 5,160 3,422 Foreign-derived intangible income ( 2,935 ) — — Loss of tax attributes 8,255 — — Provision for income taxes $ 1,998 $ 3,562 $ 745 The Company is subject to a corporate tax rate in Ireland of 25 % for non-trading activities and 12.5 % for trading activities. For the years ended December 31, 2022, 2021, and 2020 , the Company applied the statutory corporate tax rate of 25 % for Amarin Corporation plc, reflecting the non-trading tax rate in Ireland. However, for Amarin Pharmaceuticals Ireland Limited, a wholly-owned subsidiary of Amarin Corporation plc, the Company applied the 12.5 % Irish trading tax rate. In the table above, the Company used Amarin Corporat ion plc’s 25% tax rate as the starting point for the reconciliation since it is the parent entity of the business. On August 16, 2022, the Inflation Reduction Act of 2022, or the Act, was signed into law by the Biden Administration, with tax provisions effective January 1, 2023 primarily focused on implementing a 15% minimum tax on global adjusted financial statement income (CAMT) and a 1% excise tax on share repurchases. While we are still evaluating the impact of the Act, we do not expect either of these provisions to have a material impact on our financial results. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security Act, or CARES Act, was enacted in the United States. Among other provisions, the CARES Act allows businesses to carry back net operating losses arising in years 2018 to 2020 to the five prior tax years. We recorded an income tax benefit of $ 2.5 million for the year ended December 31, 2020 as a result of these loss carrybacks and an income tax benefit of nil for the years ended December 31, 2022 and 2021, respectively. In April 2016, the Company adopted ASU No. 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Share-Based Payment Accounting which changes the accounting for certain aspects of share-based payments to employees. One aspect of the standard requires that excess tax benefits and deficiencies that arise upon vesting or exercise of share-based payments be recognized as an income tax benefit and expense in the income statement. Previously, such amounts were recognized as an increase and decrease in additional paid-in capital. This aspect of the standard was adopted prospectively, and accordingly the provisions for income taxes for the years ended December 31, 2022, 2021 and 2020 includes $ 0.6 million, $ 0.1 million and $ 3.7 million of excess tax benefits, respectively, arising from share-based payments during the period. The income tax effect of each type of temporary difference comprising the net deferred tax asset as of December 31, 2022 and 2021 is as follows: In thousands December 31, 2022 December 31, 2021 Deferred tax assets: Net operating losses $ 136,862 $ 127,378 Stock-based compensation 11,616 8,563 Tax credits 2,639 15,803 Capitalized R&D 4,723 — Lease liability 2,583 2,348 Other reserves and accrued liabilities 11,895 11,257 Gross deferred tax assets 170,318 165,349 Less: valuation allowance ( 165,378 ) ( 160,295 ) Total deferred tax assets 4,940 5,054 Deferred tax liabilities: Depreciation and amortization ( 3,337 ) ( 3,404 ) Lease asset ( 1,603 ) ( 1,639 ) Other liabilities — ( 11 ) Total deferred tax liabilities ( 4,940 ) ( 5,054 ) Net deferred tax assets $ — $ — The Company assesses whether it is more-likely-than-not that the Company will realize its deferred tax assets. The Company determined that it was more-likely-than-not that the Irish, U.S., Germany, and Israeli net operating losses and the related deferred tax assets would not be realized in future periods and a full valuation allowance has been provided for all periods. The following table reflects the activity in the valuation allowance for the years ended December 31, 2022 and 2021: In thousands 2022 2021 Beginning valuation allowance $ 160,295 $ 160,841 Increase as reflected in income tax expense 12,942 2,899 Foreign exchange ( 7,859 ) ( 3,445 ) Ending valuation allowance $ 165,378 $ 160,295 During 2022, the Company recorded adjustments to its deferred tax accounts related to the impact of foreign exchange rate changes and to reconcile the financial statement accounts to the amounts expected to result in future income and deductions under local law, primarily as it relates to Irish net operating losses and deferred taxes for stock compensation. These adjustments were fully offset with valuation allowances based on the Company’s position with respect to the realizability of its recorded deferred tax assets. The Company has combined U.S. and Non-U.S. net operating loss carryforwards of $ 834.4 million, which do not expire. The total net operating loss carryforwards decreased by approximately $ 15.6 million from the prior year primarily as a result of current year loss generated by the Company’s U.S. and Non-U.S. subsidiaries, the impact of foreign exchange rate changes, and adjustments to reconcile the financial statement accounts to the amounts reported on the filed 2021 foreign tax returns. In addition, the Company has U.S. Federal tax credit carryforwards of $ 9.5 million and state tax credit carryforwards of $ 3.7 million. These amounts exclude the impact of any unrecognized tax benefits and valuation allowances. These carryforwards, which will expire between 2023 and 2042 , may be used to offset future taxable income, if any. As of December 31, 2022 , there are no earnings that have been retained indefinitely for reinvestment by foreign subsidiary; therefore, no provision has been made for income taxes that would be payable upon the distribution of such earnings or the recovery of the Company’s investment in its subsidiaries as the amount of the related unrecognized deferred income tax liability is zero . The Company's and its subsidiaries' income tax returns are periodically examined by various taxing authorities. The Company is currently under audit by the IRS for the Company’s 2018 U.S. income tax return, by the New Jersey Department of Treasury for the years 2012 to 2015 and by the New York Department of Finance for the years 2018 and 2019. Although the outcome of tax audits is always uncertain and could result in significant cash tax payments, the Company does not believe the outcome of these audits will have a material adverse effect on the Company's consolidated financial position or results of operations.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2022
Retirement Benefits [Abstract]
Defined Contribution Plan	(11) Defined Contribution Plan The Company makes available a 401(k) plan for its U.S. employees. Under the 401(k) plan, employees may make contributions which are eligible for a discretionary percentage match, in cash, as defined in the 401(k) plan and determined by the Board of Directors. The Company recognized $ 1.7 million, $ 1.9 million and $ 1.7 million of related compensation expense for the years ended December 31, 2022, 2021 and 2020 , respectively.

Co-Promotion Agreement

Co-Promotion Agreement	12 Months Ended
	Dec. 31, 2022
Co Promotion Agreement [Abstract]
Co-Promotion Agreement	(12) Co-Promotion Agreement On March 31, 2014, the Company entered into a Co-Promotion Agreement, or the Agreement, with Kowa Pharmaceuticals America, Inc. related to the commercialization of VASCEPA capsules in the United States. The Company and Kowa Pharmaceuticals America, Inc. intentionally designed the Agreement to naturally end as of December 31, 2018 and mutually agreed not to renew the Agreement. During 2018, which was the last year of the co-promotion of VASCEPA by Kowa Pharmaceuticals America, Inc., the Company incurred expense for co-promotion tail payments which are calculated as a percentage of the 2018 co-promotion fee, which was eighteen and a half percent ( 18.5 %) of VASCEPA gross margin in 2018. The accrued tail payments are paid over three years with declining amounts each year. Kowa Pharmaceuticals America, Inc. was eligible to receive $ 17.8 million in co-promotion tail payments, the present value of which $ 16.6 million, was fully accrued as of December 31, 2018. During the first quarter of 2022, the final co-promotion tail payment was made to Kowa Pharmaceuticals America, Inc. As of December 31, 2021, the Company recognized a net payable to Kowa Pharmaceuticals America, Inc. of $ 0.6 million was classified as current on the consolidated balance sheets, representing the remaining accrued co-promotion tail payments.

Revenue Recognition

Revenue Recognition	12 Months Ended
	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Revenue Recognition	(13) Revenue Recognition The Company sells VASCEPA principally to a limited number of major wholesalers, as well as selected regional wholesalers and specialty pharmacy providers in the United States and Europe, or collectively, its distributors or its customers, that in turn resell VASCEPA to retail pharmacies for subsequent resale to patients and healthcare providers. Patients are required to have a prescription in order to purchase VASCEPA. In addition to distribution agreements with distributors, the Company enters into arrangements with health care providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks and discounts with respect to the purchase of the Company’s product. Revenues from product sales are recognized when the distributor obtains control of the Company’s product, which occurs at a point in time, typically upon delivery to the distributor or customer. Payments from distributors are generally received 30 - 60 days from the date of sale. The Company evaluates the creditworthiness of each of its distributors to determine whether revenues can be recognized upon delivery, subject to satisfaction of the other requirements, or whether recognition is required to be delayed until receipt of payment. The Company calculates gross product revenues generally based on the wholesale acquisition cost or list price that the Company charges its distributors for VASCEPA. Reserves for Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established and which result from (a) trade allowances, such as invoice discounts for prompt pay and distributor fees, (b) estimated government and private payor rebates and chargebacks and discounts, such as Medicaid reimbursements, (c) reserves for expected product returns and (d) estimated costs of incentives that are offered within contracts between the Company and its distributors, health care providers, payors and other indirect customers relating to the Company’s sales of its product. These reserves are based on individual contractual amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (distributor payments or credits) or as a current liability (payable to a non-distributor). Where appropriate, these estimates take into consideration a range of possible outcomes which are probability-weighted for relevant factors such as the Company’s historical experience, current contractual and statutory requirements, specific known market events and trends, industry data and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. The amount of variable consideration which is included in the transaction price may be constrained, and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company adjusts these estimates, which would affect net product revenue and earnings in the period such variances become known. Trade Allowances: The Company generally provides invoice discounts on VASCEPA sales to its distributors for prompt payment and fees for distribution services, such as fees for certain data that distributors provide to the Company. The payment terms for sales to distributors in the U.S. and Germany generally include a 2 - 3 % discount for prompt payment while the fees for distribution services are based on contractual rates agreed with the respective distributors. Based on historical data, the Company expects its distributors to earn these discounts and fees and deducts the full amount of these discounts and fees from its gross product revenues and accounts receivable at the time such revenues are recognized. Rebates, Chargebacks and Discounts: The Company contracts with Medicaid, Medicare, other government agencies and various private organizations, or collectively, Third-party Payors, so that VASCEPA will be eligible for purchase by, for partial or full reimbursement from, such Third-party Payors. The Company estimates the rebates, chargebacks and discounts it will provide to Third-party Payors and deducts these estimated amounts from its gross product revenues at the time the revenues are recognized. The Company estimates these reserves based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability, which is included in Accrued expenses and other current liabilities on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company estimates the rebates, chargebacks and discounts that it will provide to Third-party Payors based upon (i) the Company’s contracts with these Third-party Payors, (ii) the government-mandated discounts applicable to government-funded programs, (iii) information obtained from the Company’s distributors and (iv) information obtained from other third parties regarding the payor mix for VASCEPA. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. Product Returns: The Company’s distributors have the right to return unopened unprescribed VASCEPA during the 18-month period beginning six months prior to the labeled expiration date and ending 12 months after the labeled expiration date. The expiration date for VASCEPA 1-gram and 0.5-gram size capsules is currently four years and three years , respectively, after being converted into capsule form, which is the last step in the manufacturing process for VASCEPA and generally occurs within a few months before VASCEPA is delivered to distributors. The Company estimates future product returns on sales of VASCEPA based on: (i) data provided to the Company by its distributors (including weekly reporting of distributors’ sales and inventory held by distributors that provided the Company with visibility into the distribution channel in order to determine what quantities were sold to retail pharmacies and other providers), (ii) information provided to the Company from retail pharmacies, (iii) data provided to the Company by a third-party data provider which collects and publishes prescription data, and other third parties, (iv) historical industry information regarding return rates for similar pharmaceutical products, (v) the estimated remaining shelf life of VASCEPA previously shipped and currently being shipped to distributors and (vi) contractual agreements intended to limit the amount of inventory maintained by the Company’s distributors. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in Accrued expenses and other current liabilities on the consolidated balance sheets. Other Incentives: Other incentives that the Company offers to indirect customers include co-pay mitigation rebates provided by the Company to commercially insured patients who have coverage for VASCEPA and who reside in states that permit co-pay mitigation programs. The Company’s co-pay mitigation program is intended to reduce each participating patient’s portion of the financial responsibility for VASCEPA’s purchase price to a specified dollar amount. Based upon the terms of the program and information regarding programs provided for similar specialty pharmaceutical products, the Company estimates the average co-pay mitigation amounts and the percentage of patients that it expects to participate in the program to establish its accruals for co-pay mitigation rebates. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in Accrued expenses and other current liabilities on the consolidated balance sheets. The Company adjusts its accruals for co-pay mitigation rebates based on actual redemption activity and estimates regarding the portion of issued co-pay mitigation rebates that it estimates will be redeemed. The following tables summarize activity in each of the net product revenue allowance and reserve categories described above for the years ended December 31, 2022 and 2021: In thousands Trade Rebates, Product Other Total Balance as of January 1, 2021 $ 36,242 $ 141,200 $ 7,798 $ 5,584 $ 190,824 Provision related to current period sales 121,378 684,010 1,531 45,501 852,420 Provision related to prior period sales — ( 2,034 ) — — ( 2,034 ) Credits/payments made for current period sales ( 36,473 ) ( 504,210 ) — ( 42,754 ) ( 583,437 ) Credits/payments made for prior period sales ( 34,511 ) ( 134,210 ) ( 1,240 ) ( 5,586 ) ( 175,547 ) Balance as of December 31, 2021 86,636 184,756 8,089 2,745 282,226 Provision related to current period sales 96,340 676,816 2,347 26,612 802,115 Provision related to prior period sales — 592 — — 592 Credits/payments made for current period sales ( 54,952 ) ( 548,783 ) — ( 24,671 ) ( 628,406 ) Credits/payments made for prior period sales ( 83,398 ) ( 177,288 ) ( 1,690 ) ( 2,630 ) ( 265,006 ) Balance as of December 31, 2022 $ 44,626 $ 136,093 $ 8,746 $ 2,056 $ 191,521 Such net product revenue allowances and reserves are included within Accrued expenses and other current liabilities within the consolidated balance sheets, with the exception of trade allowances and chargebacks, which are included within Accounts receivable, net as discussed above. Licensing Revenue The Company enters into licensing agreements which are within the scope of Topic 606, under which it licenses certain rights to VASCEPA for uses that are currently commercialized and under development by the Company. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory and commercial milestone payments; payments for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. Each of these payments results in licensing and royalty revenues. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. In determining performance obligations, management evaluates whether the license is distinct from the other performance obligations with the collaborative partner based on the consideration of the relevant facts and circumstances for each arrangement. Factors considered in the determination include the stage of development of the license delivered, research and development capabilities of the partner and the ability of partners to develop and commercialize VASCEPA independent of the Company. Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone Payments: At the inception of each arrangement that includes development, regulatory and commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the respective milestone as well as the level of effort and investment required. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development, regulatory and commercial milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect licensing revenues and earnings in the period of adjustment. The Company receives payments from its customers based on billing schedules established in each contract. Up-front payments and fees are recorded as deferred revenue upon receipt or when due, and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

Development, Commercialization

Development, Commercialization and Supply Agreements	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Development, Commercialization and Supply Agreements	(14) Development, Commercialization and Supply Agreements In-licenses Mochida Pharmaceutical Co., Ltd. In June 2018, the Company entered into a collaboration with Mochida Pharmaceutical Co., Ltd., or Mochida, related to the development and commercialization of drug products and indications based on the active pharmaceutical ingredient in VASCEPA, the omega-3 acid, EPA, or eicosapentaenoic acid. Among other terms in the agreement, the Company obtained an exclusive license to certain Mochida intellectual property to advance the Company’s interests in the United States and certain other territories and the parties will collaborate to research and develop new products and indications based on EPA for the Company’s commercialization in the United States and certain other territories. The potential new product and indication opportunities contemplated under this agreement are currently in early stages of development. Upon closing of the collaboration agreement, the Company made a non-refundable, non-creditable upfront payment of approximately $ 2.7 million. In addition, the agreement provides for the Company to pay milestone payments upon the achievement of certain product development milestones and royalties on net sales of future products arising from the collaboration, if any. In January 2022 and 2021, the Company exercised certain rights under the agreement, resulting in payments of $ 1.0 million, respectively, to Mochida, which was recorded as Research and development expense in the consolidated statement of operations. Out-licenses Eddingpharm (Asia) Macao Commercial Offshore Limited In February 2015, the Company entered into a Development, Commercialization and Supply Agreement, or the DCS Agreement, with Eddingpharm (Asia) Macao Commercial Offshore Limited, or Edding, related to the development and commercialization of VASCEPA in Mainland China, Hong Kong, Macau and Taiwan, or the China Territory. Under the terms of the DCS Agreement, the Company granted to Edding an exclusive (including as to the Company) license with right to sublicense to develop and commercialize VASCEPA in the China Territory for uses that are currently commercialized and under development by the Company based on the Company’s MARINE, ANCHOR and REDUCE-IT clinical trials of VASCEPA. Under the DCS Agreement, Edding is solely responsible for development and commercialization activities in the China Territory and associated expenses. The Company provides development assistance and is responsible for supplying finished and later bulk drug product at defined prices under negotiated terms. The Company retains all VASCEPA manufacturing rights. Edding agreed to certain restrictions regarding the commercialization of competitive products globally and the Company agreed to certain restrictions regarding the commercialization of competitive products in the China Territory. The Company and Edding agreed to form a joint development committee to oversee regulatory and development activities for VASCEPA in the China Territory in accordance with a negotiated development plan and formed a separate joint commercialization committee in advance of expected approval in the China Territory to oversee VASCEPA planning and pre-launch commercialization activities in the China Territory. Development costs are paid by Edding to the extent such costs are incurred in connection with the negotiated development plan or otherwise incurred by Edding. Edding is responsible for preparing and filing regulatory applications in all countries of the China Territory at Edding’s cost with the Company’s assistance. The DCS Agreement also contains customary provisions regarding indemnification, supply, record keeping, audit rights, reporting obligations, and representations and warranties that are customary for an arrangement of this type. The term of the DCS Agreement expires, on a product-by-product basis, upon the later of (i) the date on which such product is no longer covered by a valid claim under a licensed patent in the China Territory, or (ii) the 12th anniversary of the first commercial sale of such product in Mainland China. The DCS Agreement may be terminated by either party in the event of a bankruptcy of the other party and for material breach, subject to customary cure periods. In addition, at any time following the third anniversary of the first commercial sale of a product in Mainland China, Edding has the right to terminate the DCS Agreement for convenience with 12 months’ prior notice. Neither party may assign or transfer the DCS Agreement without the prior consent of the other party, provided that the Company may assign the DCS Agreement in the event of a change of control transaction. Upon closing of the DCS Agreement, the Company received a non-refundable $ 15.0 million up-front payment. In March 2016, Edding submitted its clinical trial application, or CTA, with respect to the MARINE indication for VASCEPA to the Chinese regulatory authority. Following the CTA submission, the Company received a non-refundable $ 1.0 million milestone payment. In March 2017, the CTA was approved by the Chinese regulatory authority, and, in December 2017, Edding commenced a pivotal clinical trial aimed to support the regulatory approval of the first indication of VASCEPA in a patient population with severe hypertriglyceridemia in Mainland China. In November 2020, the Company announced statistically significant topline results from the Phase 3 clinical trial of VASCEPA conducted by Edding, which is being used to seek regulatory approval in Mainland China. The Company received approval of VASCEPA under the REDUCE-IT indication in Hong Kong in February 2022. In addition to the non-refundable, up-front and regulatory milestone payments described above, the Company is entitled to receive certain regulatory and sales-based milestone payments of up to an additional $ 153.0 million as well as tiered double-digit percentage royalties on net sales of VASCEPA in the China Territory escalating to the high teens. The regulatory milestone events relate to the submission and approval of certain applications to the applicable regulatory authority, such as a clinical trial application, clinical trial exemption, or import drug license application. The amounts to be received upon achievement of the regulatory milestone events relate to the submission and approval for three indications, and range from $ 2.0 million to $ 15.0 million for a total of $ 33.0 million. The sales-based milestone events occur when annual aggregate net sales of VASCEPA in the territory equals or exceeds certain specified thresholds, and range from $ 5.0 million to $ 50.0 million for a total of $ 120.0 million. Each such milestone payment shall be payable only once regardless of how many times the sales milestone event is achieved. Each such milestone payment is non-refundable and non-creditable against any other milestone payments. The Company assessed this arrangement in accordance with Topic 606 and concluded that the contract counterparty, Edding, is a customer. The Company identified the following performance obligations at the inception of the DCS Agreement: (1) the exclusive license to develop and commercialize VASCEPA in the China Territory for uses that are currently commercialized and under development by the Company, (2) the obligation to participate in various steering committees, and (3) ongoing development and regulatory assistance. Based on the analysis performed, the Company concluded that the identified performance obligations are not distinct and therefore a combined performance obligation. The transaction price includes the $ 15.0 million up-front consideration received and the $ 1.0 million milestone payment received related to the successful submission of the CTA for the MARINE indication. None of the other clinical or regulatory milestones have been included in the transaction price, as all milestone amounts are fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones including royalties, will be recognized when the related sales occur and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. During the years ended December 31, 2022 and 2021, the Company recognized $ 0.6 million and $ 1.1 million, respectively, as licensing revenue related to the up-front and milestone payments received in connection with the Edding agreement. From contract inception through December 31, 2022 and 2021, the Company recognized $ 7.7 million and $ 7.1 million, respectively, as licensing revenue under the DCS Agreement concurrent with the input measure of support hours provided by the Company to Edding in achieving the combined development and regulatory performance obligation, which in the Company’s judgment is the best measure of progress towards satisfying this performance obligation. The remaining transaction price of $ 9.3 million and $ 9.8 million is recorded in deferred revenue as of December 31, 2022 and 2021 , respectively, on the consolidated balance sheets and will be recognized as revenue over the remaining period of 12 years . The Company recognized net product revenue of $ 0.2 million and $ 0.3 million for the years ended December 31, 2022 and 2021, respectively, related to sales to Edding. Biologix FZCo In March 2016, the Company entered into an agreement with Biologix FZCo, or Biologix, a company incorporated under the laws of the United Arab Emirates, to register and commercialize VASCEPA in several Middle Eastern and North African countries. Under the terms of the distribution agreement, the Company granted to Biologix a non-exclusive license to use its trademarks in connection with the importation, distribution, promotion, marketing and sale of VASCEPA in the Middle East and North Africa territory. Upon closing of the agreement, the Company received a non-refundable up-front payment, which will be recognized as revenue over 10 years commencing upon first marketing approval of VASCEPA in the territory. The Company is entitled to receive all payments based on total product sales and pays Biologix a service fee in exchange for its services, whereby the service fee represents a percentage of gross selling price which is subject to a minimum floor price. The Company received approval of VASCEPA under the MARINE and REDUCE-IT indications in the following countries: Country MARINE REDUCE-IT Launch Date Lebanon March 2018 August 2021 June 2018 United Arab Emirates July 2018 October 2021 February 2019 Qatar December 2019 April 2021 — Bahrain April 2021 April 2022 — Kuwait December 2021 — — Saudi Arabia March 2022 — — The Company recognized net product revenue of approximately $ 1.0 million and $ 1.4 million as of December 31, 2022 and 2021, respectively, related to sales to Biologix. HLS Therapeutics, Inc. In September 2017, the Company entered into an agreement with HLS Therapeutics Inc., or HLS, a company incorporated under the laws of Canada, to register, commercialize and distribute VASCEPA in Canada. Under the agreement, HLS will be responsible for regulatory and commercialization activities and associated costs. The Company is responsible for providing assistance towards local filings, supplying finished product under negotiated supply terms, maintaining intellectual property, and continuing the development and funding of REDUCE-IT related activities. Upon closing of the agreement, the Company received one-half of a non-refundable $ 5.0 million up-front payment, and received the remaining half on the six-month anniversary of the closing. Following achievement of the REDUCE-IT trial primary endpoint, which was announced in September 2018, the Company received a non-refundable $ 2.5 million milestone payment. Following approval from Health Canada in December 2019, the Company received a non-refundable milestone payment of $ 2.5 million in February 2020. In addition, in January 2020 HLS obtained regulatory exclusivity from the Office of Patented Medicines and Liaison, or OPML, as a result the Company received a non-refundable $ 3.8 million milestone payment. In addition to the non-refundable, up-front and regulatory milestone payments just described, the Company is entitled to receive certain sales-based milestone payments of up to an additional $ 50.0 million, as well as tiered double-digit royalties on net sales of VASCEPA in Canada. The Company assessed this arrangement in accordance with Topic 606 and concluded that the contract counterparty, HLS, is a customer. The Company identified the following performance obligations at the inception of the contract: (1) license to HLS to develop, register, and commercialize VASCEPA in Canada, (2) support general development and regulatory activities, and (3) participate in various steering committees. Based on the analysis performed, the Company concluded that the identified performance obligations in the agreement are not distinct and therefore a combined performance obligation. The transaction price includes the $ 5.0 million up-front consideration, the $ 2.5 million milestone related to the achievement of the REDUCE-IT trial primary endpoint, the $ 2.5 million milestone related to obtaining approval from Health Canada and $ 3.8 million milestone related to obtaining regulatory exclusivity from the OPML. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. During the years ended December 31, 2022 and 2021, the Company recognized $ 0.7 million and $ 0.9 million, respectively, as licensing revenue related to up-front and milestone payments received in connection with the HLS agreement. From the contract’s inception through December 31, 2022 and 2021, the Company has recognized $ 8.2 million and $ 7.5 million, respectively, as licensing revenue is recognized under the agreement concurrent with the input measure of support hours provided by the Company to HLS in achieving this performance obligation, which in the Company’s judgment is the best measure of progress towards satisfying the combined development and regulatory performance obligation. The remaining transaction price of $ 5.6 million and $ 6.2 million is recorded in deferred revenue as of December 31, 2022 and 2021 , respectively, on the consolidated balance sheets and will be recognized as revenue over the remaining period of 8 years . The Company recognized net product revenue of $ 2.9 million and nil for the years ended December 31, 2022 and 2021, respectively, related to sales to HLS. CSL Seqirus In February 2023, the Company entered into an agreement with CSL Seqirus to secure pricing and reimbursement, commercialize and distribute VAZKEPA in Australia and New Zealand. The Company will receive an upfront payment of $ 0.5 million and be eligible to receive event-related milestone payments of approximately $ 8.0 million and additional product-related milestone payments of approximately $ 4.0 million. The Company will be responsible for supplying finished product to CSL Seqirus at a profitable transfer price. The following table presents changes in the balances of the Company’s contract assets and liabilities for years ended December 31, 2022 and 2021: In thousands Balance at Additions Deductions Balance at Year ended December 31, 2022: Contract assets $ — $ — $ — $ — Contract liabilities: Deferred revenue $ 16,709 $ 6 $ ( 1,369 ) $ 15,346 Year ended December 31, 2021: Contract assets $ — $ — $ — $ — Contract liabilities: Deferred revenue $ 18,632 $ 128 $ ( 2,051 ) $ 16,709 During the years ended December 31, 2022 and 2021, the Company recognized the following revenues as a result of changes in the contract asset and contract liability balances in the respective periods: In thousands Twelve Months Ended December 31, Revenue recognized in the period from: 2022 2021 Amounts included in contract liability at the beginning of the period $ 1,366 $ 1,997 Performance obligations satisfied in previous periods $ 2 $ 46

Leases

Leases	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Leases	(15) Leases The Company leases office space under operating leases. The lease liability is initially measured at the present value of the lease payments to be made over the lease term. Lease payments are comprised of the fixed and variable payments to be made by the Company to the lessor during the lease term minus any incentives or rebates or abatements receivable by the Company from the lessor or the owner. Payments for non-lease components do not form part of lease payments. The lease term includes renewal options only if these options are specified in the lease agreement and if failure to exercise the renewal option imposes a significant economic penalty for the Company. As there are no significant economic penalties, renewal cannot be reasonably assured and the lease terms for the office space do not include any renewal options. The Company has not entered into any leases with related parties. The Company accounts for short-term leases (i.e., lease term of 12 months or less) by making the short-term lease policy election and will not apply the recognition and measurement requirements of ASC 842. The Company has determined that the rate implicit in the lease is not determinable and the Company does not have borrowings with similar terms and collateral. Therefore, the Company considered a variety of factors, including the Company’s credit rating, observable debt yields from comparable companies with a similar credit profile and the volatility in the debt market for securities with similar terms, in determining that 11.5 % was reasonable to use as the incremental borrowing rate for purposes of the calculation of lease liabilities and a change of 1 % would not result in a material change to the Company’s consolidated financial statements. On February 5, 2019, the Company entered into a lease agreement for new office space in Bridgewater, New Jersey, or the Lease. The Lease commenced on August 15, 2019 , or the Commencement Date, for an 11 -year period, with two five-year renewal options. Subject to the terms of the Lease, Amarin will have a one-time option to terminate the agreement effective on the first day of the 97 th month after the Commencement Date upon advance written notice and a termination payment specified in the Lease. Under the Lease, the Company paid monthly rent of approximately $ 0.1 million for the first year following the Commencement Date, and such rent increases by a nominal percentage every year following the first anniversary of the Commencement Date. In addition, Amarin receives certain abatements subject to the limitations in the Lease. On November 17, 2021, the Company entered into a lease agreement for new office space in Zug Switzerland, or the Zug Lease. The Zug Lease commenced on February 1, 2022 , or the Zug Commencement Date, for a 5-year period, with one five-year renewal option. Under the Zug Lease, the Company will pay annual rent of approximately $ 0.2 million for the first year following the Zug Commencement Date, and such rent increases by a nominal percentage every year following the first anniversary of the Zug Commencement Date. On September 13, 2022, the Company entered into a lease agreement for new office space in Dublin, Ireland, or the Dublin Lease. The Dublin Lease commenced on October 1, 2022 , or the Dublin Commencement Date, for a 2-year period. Under the Dublin Lease, the Company will pay annual rent of approximately $ 0.4 million during the duration of the lease term. In addition to the real estate leases, the Company leases various vehicles with terms ranging from month to month up to 36 months . The operating lease liability is $ 11.6 million and $ 10.3 million and the operating lease right-of-use asset is $ 9.1 million and $ 7.7 million, as of December 31, 2022 and 2021, respectively. The lease expense for the years ended December 31, 2022, 2021 and 2020 is approximately $ 2.8 million, $ 2.2 million and $ 1.6 million, respectively. The table below depicts a maturity analysis of the Company’s undiscounted payments for its operating lease liabilities and their reconciliation with the carrying amount of lease liability presented in the statement of financial position as of December 31, 2022: Undiscounted 2023 $ 2,796 2024 2,572 2025 2,096 2026 2,131 2027 1,962 2028 and thereafter 5,251 Total undiscounted payments $ 16,808 Discount Adjustments $ ( 5,227 ) Current operating lease liability 1,566 Long-term operating lease liability $ 10,015 The Company entered into a sublease agreement to lease a portion of the Bridgewater, New Jersey facility. The lease commenced on February 1, 2023 , or the Sublease Commencement Date, for a seven and a half year period . Under the sublease, the Company will receive monthly rent payments of approximately $ 0.1 million during the first year, and such rent increases by a nominal percentage every year following the first anniversary of the Sublease Commencement Date.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates Accounting estimates are based on historical experience and other factors that are considered reasonable under the circumstances. Estimates and assumptions relied upon in preparing these consolidated financial statements relate to, but are not limited to, such items as provisions for sales returns, rebates and incentives, chargebacks, and other sales allowances; depreciable/amortizable lives; asset impairments; valuation allowance on deferred taxes; probabilities of achievement of performance conditions for certain equity awards; amounts recorded for licensing revenue; contingencies and accruals. Because of the uncertainties inherent in such estimates, actual results may differ from these estimates. Management periodically evaluates estimates used in the preparation of the consolidated financial statements for continued reasonableness.
Use of Forecasted Financial Information in Accounting Estimates	Use of Forecasted Financial Information in Accounting Estimates The use of forecasted financial information is inherent in many of the Company’s accounting estimates including, but not limited to, determining the estimated fair values of intangible assets, evaluating the need for valuation allowances for deferred tax assets, and assessing the Company’s ability to continue as a going concern. Such forecasted financial information is comprised of numerous assumptions regarding the Company’s future revenues, cash flows, and operational results. Management believes that its financial forecasts are reasonable and appropriate based upon current facts and circumstances. Because of the inherent nature of forecasts, however, actual results may differ from these forecasts. Management regularly reviews the information related to these forecasts and adjusts the carrying amounts of the applicable assets prospectively, if and when actual results differ from previous estimates.
Revenue Recognition	Revenue Recognition In accordance with Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers , or Topic 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services committed within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. For a complete discussion of accounting for net product revenue and licensing revenue, see Note 13—Revenue Recognition.
Distribution Costs	Distribution Costs The Company records distribution costs related to shipping product to its customers, primarily through the use of common carriers or external distribution services, in Cost of goods sold.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash Cash and cash equivalents consist of cash, deposits with banks and short-term highly liquid money market instruments with original maturities at the date of purchase of 90 days or less. Restricted cash represents cash and cash equivalents pledged to guarantee repayment of certain expenses which may be incurred for business travel under corporate credit cards held by employees.
Accounts Receivable, net	Accounts Receivable, net Accounts receivable, net, comprised of trade receivables, are generally due within 45 days and are stated at amounts due from customers. The Company recognizes an allowance for losses on accounts receivable in an amount equal to the estimated probable losses net of any recoveries. The allowance is based primarily on assessment of specific identifiable customer accounts considered at risk or uncollectible, as well as an analysis of current receivables aging and expected future write-offs. The expense associated with the allowance for doubtful accounts is recognized as Selling, general, and administrative expense. The Company has not historically experienced any significant credit losses. All customer accounts are actively managed and no losses in excess of amounts reserved are currently expected; however, the Company is monitoring the potential negative impact of COVID-19 on the Company’s customers’ ability to meet their financial obligations. The following table summarizes the impact of accounts receivable reserves on the gross trade accounts receivable balances at December 31, 2022 and 2021: In thousands December 31, 2022 December 31, 2021 Gross trade accounts receivable $ 187,418 $ 262,948 Trade allowances ( 44,626 ) ( 86,636 ) Chargebacks ( 11,802 ) ( 11,714 ) Allowance for doubtful accounts — ( 945 ) Accounts receivable, net $ 130,990 $ 163,653
Inventory	Inventory The Company states inventories at the lower of cost or net realizable value. Cost is determined based on actual cost using the average cost method. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company classifies inventory as long-term inventory when consumption of the finished goods and work in process inventory is expected beyond the normal operating cycle. The Company classifies finished goods expected to be consumed within a normal operating cycle and all of VASCEPA's active pharmaceutical ingredient, or API, as current inventory. An allowance is established when management determines that certain inventories may not be saleable. If inventory cost exceeds expected net realizable value due to obsolescence, damage or quantities in excess of expected demand, changes in price levels or other causes, the Company will reduce the carrying value of such inventory to net realizable value and recognize the difference as a component of cost of goods sold in the period in which it occurs. The Company capitalizes inventory purchases of saleable product from approved suppliers while inventory purchases from suppliers prior to regulatory approval are included as a component of research and development expense. The Company expenses inventory identified for use as marketing samples when they are packaged. The average cost reflects the actual purchase price of VASCEPA API.
Long-Lived Asset Impairment	Long-Lived Asset Impairment The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of these assets is determined by comparing the forecasted undiscounted net cash flows of the operation to which the assets relate to their carrying amount. If impairment is indicated, the assets are written down to fair value. Fair value is determined based on discounted forecasted cash flows or appraised values, depending on the nature of the assets.
Intangible Asset, net	Intangible Asset, net Intangible asset, net consists of website development costs and milestone payments to the former shareholders of Laxdale Limited, or Laxdale, related to the 2004 acquisition of the rights to VASCEPA, which is the result of VASCEPA receiving marketing approval in the U.S. for the first indication in 2012, the expanded label in 2019 and marketing authorization in Europe in 2021. These assets are amortized over its estimated useful life on a straight-line basis. See Note 7—Commitments and Contingencies for further information regarding other obligations related to the acquisition of Laxdale.
Costs for Patent Litigation and Legal Proceedings	Costs for Patent Litigation and Legal Proceedings Costs for patent litigation or other legal proceedings are expensed as incurred and included in Selling, general and administrative expense.
Research and Development Costs	Research and Development Costs The Company charges research and development costs to operations as incurred. Research and development expenses are comprised of costs incurred by the Company in performing research and development activities, including: salary and benefits; stock-based compensation expense; laboratory supplies and other direct expenses; contractual services, including clinical trial and pharmaceutical development costs; commercial supply investment in its drug candidates; and infrastructure costs, including facilities costs and depreciation expense. In addition, research and development costs include the costs of product supply received from suppliers when such receipt by the Company is prior to regulatory approval of the supplier, as well as license fees related to the Company’s strategic collaboration with Mochida Pharmaceutical Co., Ltd., or Mochida.
Selling, General and Administrative Costs	Selling, General and Administrative Costs The Company charges selling, general and administrative costs to operations as incurred. Selling, general and administrative costs include salaries and benefits, stock-based compensation expense, and costs of programs and infrastructure necessary for the general conduct of the Company’s business, including those incurred as a result of the commercialization of VASCEPA in the United States.
Income Taxes	Income Taxes Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts and tax bases of assets and liabilities and operating loss carryforwards and other tax attributes using enacted rates expected to be in effect when those differences reverse. Valuation allowances are provided against deferred tax assets that are not more likely than not to be realized. Deferred tax assets and liabilities are classified as non-current in the consolidated balance sheet. The Company provides reserves for potential payments of tax to various tax authorities and does not recognize tax benefits related to uncertain tax positions and other issues. Tax benefits for uncertain tax positions are based on a determination of whether a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized, assuming that the matter in question will be decided based on its technical merits. The Company’s policy is to record interest and penalties in the provision for income taxes, as applicable. The Company regularly assesses its ability to realize deferred tax assets. Changes in historical earnings performance, future earnings projections, and changes in tax laws, among other factors, may cause the Company to adjust its valuation allowance on deferred tax assets, which would impact the Company’s income tax expense in the period in which it is determined that these factors have changed. Excess tax benefits and deficiencies that arise upon vesting or exercise of share-based payments are recognized as an income tax benefit and expense, respectively, in the consolidated statement of operations. Excess income tax benefits are classified as cash flows from operating activities and cash paid to taxing authorities arising from the withholding of shares from employees are classified as cash flows from financing activities. The Company’s and its subsidiaries’ income tax returns are periodically examined by various tax authorities, including the Internal Revenue Service, or IRS, and states. The Company is currently under audit by the IRS for the Company’s 2018 U.S. income tax return and by the New Jersey Department of Treasury for the years 2012 to 2015 . Although the outcome of tax audits is always uncertain and could result in significant cash tax payments, the Company does not believe the outcome of these audits will have a material adverse effect on its consolidated financial position or results of operations.
(Loss) Earnings per Share	(Loss) Earnings per Share Basic net (loss) earnings per share is determined by dividing net (loss) income by the weighted average shares of common stock outstanding during the period. Diluted net (loss) earnings per share is determined by dividing net (loss) income by diluted weighted average shares outstanding. Diluted weighted average shares reflects the dilutive effect, if any, of potentially dilutive common shares, such as from the exercise of stock options and vesting of restricted stock units calculated using the treasury stock method. In periods with reported net operating losses, all stock options and restricted stock units outstanding are deemed anti-dilutive such that basic and diluted net loss per share are equal. The calculation of net (loss) income and the number of shares used to compute basic and diluted net (loss) earnings per share for the years ended December 31, 2022, 2021, and 2020 are as follows: In thousands 2022 2021 2020 Net (loss) income —basic and diluted $ ( 105,803 ) $ 7,729 $ ( 18,000 ) Weighted average shares outstanding—basic 401,155 395,992 381,759 Effect of dilutive securities: Stock options — 4,420 — Restricted stock and restricted stock units — 2,068 — Weighted average shares outstanding—diluted 401,155 402,480 381,759 Net (loss) earnings per share—basic $ ( 0.26 ) $ 0.02 $ ( 0.05 ) Net (loss) earnings per share—diluted $ ( 0.26 ) $ 0.02 $ ( 0.05 ) For the years ended December 31, 2022, 2021 and 2020, the following potentially dilutive securities were not included in the computation of net (loss) earnings per share because the effect would be anti-dilutive or because performance criteria were not yet met for awards contingent upon such measures: In thousands 2022 2021 2020 Stock options 19,182 9,926 16,664 Restricted stock and restricted stock units 14,461 3,764 7,710 Laxdale milestone shares — 1,984 — Stock options are anti-dilutive during periods of net earnings when the exercise price of the stock options exceeds the market price of the underlying shares on the last day of the reporting period. Restricted stock and restricted stock units are anti-dilutive during periods of net earnings when underlying performance-based vesting requirements were not achieved as of the last day of the reporting period.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation in accordance with the guidance of FASB ASC Topic 718, Compensation-Stock Compensation , or ASC 718, and requires the fair value of all stock-based payments to employees and non-employees to be recognized in the consolidated statement of operations over the requisite service period. The fair value of the Company's restricted stock units is determined to be the market price on the date of the grant. The Company estimates the fair value of stock option awards on the date of the grant using the Black-Scholes Model, which requires that the Company makes certain assumptions regarding: (i) the expected volatility in the market price of its common stock; (ii) dividend yield; (iii) risk-free interest rates; and (iv) the period of time employees are expected to hold the award prior to exercise, referred to as the expected holding period. As a result, if the Company revises its assumptions and estimates, stock-based compensation expense could change materially for future grants. For awards with performance conditions, if the achievement of the performance conditions is deemed probable, the Company recognizes compensation expense based on the grant date fair value of the award over the requisite service period. The Company reassesses the probability of achievement of the performance conditions each reporting period. The Company estimates the level of forfeitures expected to occur based on its historical data and records compensation cost only for those awards that are ultimately expected to vest. See Note 9—Stock Incentive Plans and Stock-Based Compensation for further discussion.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to credit risk consist primarily of cash and cash equivalents, short-term and long-term investments, and accounts receivable. The Company maintains substantially all of its cash and cash equivalents and short-term and long-term investments, in financial institutions believed to be of high-credit quality. A significant portion of the Company’s sales are to wholesalers in the pharmaceutical industry. The Company monitors the creditworthiness of customers to whom it grants credit terms and has not experienced any credit losses. The Company does not require collateral or any other security to support credit sales. Three customers individually accounted for 10% or more of the Company’s gross product sales. Customers A, B, and C accounted for 35 % , 31 % , and 27 % , respectively, of gross product sales for the year ended December 31, 2022 and represented 35 % , 21 % , and 39 % , respectively, of the gross accounts receivable balance as of December 31, 2022. Customers A, B, and C accounted for 37 % , 28 % and 27 % , respectively, of gross product sales for the year ended December 31, 2021 and represented 39 % , 22 % , and 35 % , respectively, of the gross accounts receivable balance as of December 31, 2021 . The Company has not experienced any significant write-offs of its accounts receivable. All customer accounts are actively managed and no losses are currently expected; however, the Company is monitoring the potential negative impact of COVID-19 on the Company’s customers’ ability to meet their financial obligations.
Concentration of Suppliers	Concentration of Suppliers The Company has contractual freedom to source the API for VASCEPA and to procure other services supporting its supply chain and has entered into supply agreements with multiple suppliers. The Company’s supply of product for commercial sale and clinical trials is dependent upon relationships with third-party manufacturers and suppliers. The Company cannot provide assurance that its efforts to procure uninterrupted supply of VASCEPA to meet market demand will continue to be successful or that it will be able to renew current supply agreements on favorable terms or at all. Significant alteration to or disruption or termination of the Company’s current supply chain, including as a result of COVID-19, or the Company’s failure to enter into new and similar agreements in a timely fashion, if needed, could have a material adverse effect on its business, condition (financial and other), prospects or results of operations. The Company currently has manufacturing agreements with multiple independent API manufacturers and several independent API encapsulators and packagers for VASCEPA manufacturing. Each of these API manufacturers, encapsulators and packagers is U.S. FDA-approved and certain of these API manufacturers, encapsulators and packagers are also approved by the European Regulatory Authorities for manufacturing VAZKEPA in Europe. These suppliers are also used by the Company to source supply to meet the clinical trial and commercial demands of its partners in other countries. Each of these suppliers has qualified and validated its manufacturing processes. There can be no guarantee that these or other suppliers with which the Company may contract in the future to manufacture VASCEPA or VASCEPA API will remain qualified to do so to its specifications or that these and any future suppliers will have the manufacturing capacity to meet potential global demand for VASCEPA.
Foreign Currency	Foreign Currency Monetary assets and liabilities denominated in a foreign currency are remeasured into U.S. dollars at period-end exchange rates. Gains and losses from the remeasurement are included in Other (expense) income, net in the consolidated statements of operations. For transactions settled during the applicable period, gains and losses are included in Other (expense) income, net in the consolidated statements of operations. Certain amounts payable pursuant to supply contracts are denominated in currencies other than the U.S. dollar. The Company recorded a foreign currency loss within the Other (expense) income, net on the consolidated statement of operations of $ 0.7 million, $ 0.6 million and less than $ 0.1 million for each of the years ended December 31, 2022, 2021, and 2020 , respectively.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company provides disclosure of financial assets and financial liabilities that are carried at fair value based on the price that would be received upon sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Fair value measurements may be classified based on the amount of subjectivity associated with the inputs to fair valuation of these assets and liabilities using the following three levels: Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.) and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). Level 3—Unobservable inputs that reflect the Company’s estimates of the assumptions that market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available, including its own data. The following tables present information about the estimated fair value of the Company’s assets and liabilities as of December 31, 2022 and 2021 and indicate the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value: December 31, 2022 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 81,870 $ 81,870 $ — $ — U.S. Treasury Shares 3,117 3,117 — — Agency Securities 1,554 1,554 — — Corporate Bonds 28,416 — 28,416 — Commercial Paper 62,347 — 62,347 — Repo Securities 3,250 — 3,250 — Asset Backed Securities 1,260 — 1,260 — Certificate of Deposit 9,100 — 9,100 — Non-US Government 1,393 — 1,393 — Total $ 192,307 $ 86,541 $ 105,766 $ — December 31, 2021 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 95,063 $ 95,063 $ — $ — U.S. Treasury Shares 23,219 23,219 — — Corporate Bonds 83,587 — 83,587 — Commercial Paper 121,773 — 121,773 — Repo Securities 8,000 — 8,000 — Asset Backed Securities 8,816 — 8,816 — Certificate of Deposit 21,553 — 21,553 — Non-US Government 12,900 — 12,900 — Total $ 374,911 $ 118,282 $ 256,629 $ — The carrying amount of the Company’s cash and cash equivalents approximates fair value because of their short-term nature. The cash and cash equivalents consist of cash, deposits with banks and short-term highly liquid money market instruments with remaining maturities at the date of the purchase of 90 days or less. The Company’s held-to-maturity investments are stated at amortized cost, which approximates fair value. The Company does not intend to sell these investment securities and the contractual maturities are not greater than 24 months . Those with original maturities greater than 90 days and less than 12 months are included in short-term investments on its consolidated balance sheet. Those with remaining maturities in excess of 12 months are included in long-term investments on its consolidated balance sheet. Unrealized gains or losses on held-to-maturity securities are not recognized until maturity, except other-than-temporary unrealized losses which are recognized in earnings in the period incurred. The Company evaluates securities with unrealized losses to determine whether such losses are other than temporary. The unrealized gain or loss for the year ended December 31, 2022 and December 31, 2021 were losses of $ 0.4 million and $ 0.2 million, respectively. Interest on investments is reported in interest income. The carrying amounts of accounts payable and accrued liabilities approximate fair value because of their short-term nature.
Segment and Geographical Information	Segment and Geographical Information Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated on a regular basis by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources to an individual segment and in assessing performance of the segment. The Company currently operates in one business segment, which is the development and commercialization of VASCEPA. A single management team that reports to the Company’s chief decision-maker, who is the Chief Executive Officer, comprehensively manages the business. Accordingly, the Company does not have separately reportable segments.
Restructuring	Restructuring On September 22, 2021, the Company announced a Go-to-Market strategy for VASCEPA. As part of this strategy, the Company completed a reduction of its U.S. field force to approximately 300 sales representatives, enhanced managed care access and optimized VASCEPA prescriptions for cardiovascular risk reduction. During the year ended December 31, 2021, the Company recognized approximately $ 13.7 million in charges related to the reduction in force, substantially all of which were cash expenditures for one-time termination benefits and associated costs. On June 6, 2022, the Company announced a Comprehensive Cost Reduction Plan which included an organizational restructuring plan to address shifts within the Company’s U.S. business. As part of the plan, the Company completed a reduction of its U.S. field force from approximately 300 sales representatives to approximately 75 sales representatives. During the year ended December 31, 2022 the Company recognized approximately $ 9.4 million within Restructuring expense on the consolidated statement of operations related to the Comprehensive Cost Reduction Plan, substantially all of which are cash expenditures. The Company also reviewed its contractual supplier purchase obligations and has taken steps to amend supplier agreements to align supply arrangements with current and future market demand resulting in charges of $ 18.1 million recognized within Cost of goods sold - restructuring inventory for the year ended December 31, 2022 on the consolidated statement of operations. The Company continues to negotiate with other contract suppliers to align its supply arrangements with current and future global demand which may result in additional costs to the Company. On August 19, 2022, the Company announced that after the conclusion of the fourth and final round of negotiations with the National Association of Statutory Health Insurance Funds, or GKV-SV, a viable agreement on the reimbursement price of VAZKEPA in Germany could not be reached. As a result of the negotiation outcome with the GKV-SV, the Company discontinued its German business operations effective September 1, 2022. The Company recognized approximately $ 4.2 million within Restructuring expense on the consolidated statement of operations, substantially all of which are cash expenditures. The following table sets forth the components of the Company's restructuring charges for the years ended December 31, 2022 and 2021 (none in 2020): For the Year Ended December 31, In thousands 2022 2021 Employee restructuring separation charges $ 9,310 $ 13,717 Vendor contract charges 4,216 — Total restructuring expense 13,526 13,717 Restructuring inventory 18,078 — Stock forfeitures 591 — Total restructuring costs incurred $ 32,195 $ 13,717 The following table shows the change in restructuring liability which is included within accrued expenses and other current liabilities: In thousands Restructuring Liability Balance at December 31, 2021 $ 1,186 Costs incurred 32,195 Payments ( 33,189 ) Balance at December 31, 2022 $ 192
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or FASB, and are early adopted by the Company or adopted as of the specified effective date. The Company has evaluated all recently issued accounting pronouncements through the date of the financial statements and found that no recently issued accounting pronouncements, when adopted, will have a material impact on the Company’s condensed consolidated financial position, results of operations, and cash flows, or do not apply to the Company’s operations.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Summary of Impact of Accounts Receivable Reserves on Gross Trade Accounts Receivable Balances	The following table summarizes the impact of accounts receivable reserves on the gross trade accounts receivable balances at December 31, 2022 and 2021: In thousands December 31, 2022 December 31, 2021 Gross trade accounts receivable $ 187,418 $ 262,948 Trade allowances ( 44,626 ) ( 86,636 ) Chargebacks ( 11,802 ) ( 11,714 ) Allowance for doubtful accounts — ( 945 ) Accounts receivable, net $ 130,990 $ 163,653
Calculation of Net (Loss) Income and Number of Shares Used to Compute Basic and Diluted Net (Loss) Earnings per Share	The calculation of net (loss) income and the number of shares used to compute basic and diluted net (loss) earnings per share for the years ended December 31, 2022, 2021, and 2020 are as follows: In thousands 2022 2021 2020 Net (loss) income —basic and diluted $ ( 105,803 ) $ 7,729 $ ( 18,000 ) Weighted average shares outstanding—basic 401,155 395,992 381,759 Effect of dilutive securities: Stock options — 4,420 — Restricted stock and restricted stock units — 2,068 — Weighted average shares outstanding—diluted 401,155 402,480 381,759 Net (loss) earnings per share—basic $ ( 0.26 ) $ 0.02 $ ( 0.05 ) Net (loss) earnings per share—diluted $ ( 0.26 ) $ 0.02 $ ( 0.05 )
Anti-Dilutive Securities Not Included in the Computation of Net (Loss) Earnings per Share	For the years ended December 31, 2022, 2021 and 2020, the following potentially dilutive securities were not included in the computation of net (loss) earnings per share because the effect would be anti-dilutive or because performance criteria were not yet met for awards contingent upon such measures: In thousands 2022 2021 2020 Stock options 19,182 9,926 16,664 Restricted stock and restricted stock units 14,461 3,764 7,710 Laxdale milestone shares — 1,984 —
Estimated Fair Value of Assets and Liability	The following tables present information about the estimated fair value of the Company’s assets and liabilities as of December 31, 2022 and 2021 and indicate the fair value hierarchy of the valuation techniques the Company utilized to determine such fair value: December 31, 2022 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 81,870 $ 81,870 $ — $ — U.S. Treasury Shares 3,117 3,117 — — Agency Securities 1,554 1,554 — — Corporate Bonds 28,416 — 28,416 — Commercial Paper 62,347 — 62,347 — Repo Securities 3,250 — 3,250 — Asset Backed Securities 1,260 — 1,260 — Certificate of Deposit 9,100 — 9,100 — Non-US Government 1,393 — 1,393 — Total $ 192,307 $ 86,541 $ 105,766 $ — December 31, 2021 In thousands Total Level 1 Level 2 Level 3 Asset: Money Market Fund $ 95,063 $ 95,063 $ — $ — U.S. Treasury Shares 23,219 23,219 — — Corporate Bonds 83,587 — 83,587 — Commercial Paper 121,773 — 121,773 — Repo Securities 8,000 — 8,000 — Asset Backed Securities 8,816 — 8,816 — Certificate of Deposit 21,553 — 21,553 — Non-US Government 12,900 — 12,900 — Total $ 374,911 $ 118,282 $ 256,629 $ —
Summary of Restructuring Charges	The following table sets forth the components of the Company's restructuring charges for the years ended December 31, 2022 and 2021 (none in 2020): For the Year Ended December 31, In thousands 2022 2021 Employee restructuring separation charges $ 9,310 $ 13,717 Vendor contract charges 4,216 — Total restructuring expense 13,526 13,717 Restructuring inventory 18,078 — Stock forfeitures 591 — Total restructuring costs incurred $ 32,195 $ 13,717
Change in Restructuring Liability Associated with the Plan	The following table shows the change in restructuring liability which is included within accrued expenses and other current liabilities: In thousands Restructuring Liability Balance at December 31, 2021 $ 1,186 Costs incurred 32,195 Payments ( 33,189 ) Balance at December 31, 2022 $ 192

Intangible Asset (Tables)

Intangible Asset (Tables)	12 Months Ended
	Dec. 31, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Carrying Value of Intangible Asset	The carrying value as of December 31, 2022 and 2021 is as follows: In thousands December 31, 2022 December 31, 2021 Technology rights $ 32,859 $ 32,081 Accumulated amortization ( 11,079 ) ( 8,534 ) Intangible asset, net $ 21,780 $ 23,547
Schedule of Estimated Future Amortization Expense	Estimated future amortization expense, based upon the Company’s intangible asset, as of December 31, 2022 is as follows: In thousands Year Ending December 31, Amount 2023 $ 2,805 2024 2,805 2025 2,805 2026 2,546 2027 2,546 Thereafter 8,273 Total $ 21,780

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2022
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventories as of December 31, 2022 and 2021 consist of the following: In thousands December 31, 2022 December 31, 2021 Raw materials $ 126,391 $ 107,695 Work in process 52,297 41,965 Finished goods 213,664 206,270 Inventory $ 392,352 $ 355,930

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment as of December 31, 2022 and 2021 consist of the following: In thousands Useful Life (in years) December 31, 2022 December 31, 2021 Furniture and fixtures 5 $ 1,633 $ 1,633 Leasehold improvements lesser of useful life or lease term 869 869 Software 3 - 5 617 617 Computer equipment 3 - 5 227 227 Property, plant and equipment 3,346 3,346 Accumulated depreciation and amortization ( 2,472 ) ( 1,921 ) Property, plant and equipment, net $ 874 $ 1,425

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2022
Payables and Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following as of December 31, 2022 and 2021: In thousands December 31, 2022 December 31, 2021 Payroll and payroll-related expenses $ 20,302 $ 19,730 Sales and marketing accruals 1,672 3,563 Accrued revenue allowances 135,061 184,216 All other 35,643 45,602 Accrued expenses and other current liabilities $ 192,678 $ 253,111

Equity (Tables)

Equity (Tables)	12 Months Ended
	Dec. 31, 2022
Equity [Abstract]
Summarizes the Aggregate Number of Stock Options And Restricted Stock Unit	The following table summarizes the aggregate number of stock options and restricted stock units, or RSUs, outstanding under the 2020 Plan as of December 31, 2022: December 31, 2022 Outstanding stock options 19,182,111 % of outstanding shares on a fully diluted basis 4 % Outstanding RSUs 14,461,050 % of outstanding shares on a fully diluted basis 3 %
Summary of Equity Awards Activity	The following table represents equity awards activity during the years ended December 31, 2022 and 2021: For the Year Ended December 31, 2022 2021 Common shares issued for stock option exercises 33,303 1,203,845 Gross and net proceeds from stock option exercises $ 59,686 $ 2,921,000 Common shares issued in settlement of vested RSUs 1,940,371 1,203,845 Shares retained for settlement of employee tax obligations ─ RSUs 500,064 782,917 Common shares issued in settlement of vested Performance-Based RSUs (1) — 1,923,316 Shares retained for settlement of employee tax obligations ─ Performance-Based RSUs — 816,931 (1) Performance-based RSUs vested in connection with the achievement of certain regulatory and sales performance conditions associated with the REDUCE-IT clinical trial and subsequent revenue growth. These performance-based RSUs have fully vested as of August 2021.

Stock Incentive Plans and Sto_2

Stock Incentive Plans and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Stock Option Activity	The following table summarizes all stock option activity for the year ended December 31, 2022: In thousands (except per share amounts and years) Number of Weighted Weighted Aggregate Outstanding as of January 1, 2022 18,493 $ 7.32 Granted 5,038 2.56 Forfeited ( 4,105 ) 8.39 Expired ( 211 ) 11.65 Exercised ( 33 ) 1.79 Outstanding as of December 31, 2022 19,182 5.80 6.2 years $ 158 Exercisable as of December 31, 2022 12,888 6.80 4.9 years $ 86 Vested and expected to vest as of December 31, 2022 18,867 5.83 6.2 years $ 155 Available for future grant as of December 31, 2022 15,383
Assumptions Used to Estimate Fair Value of Share-Based Payment Awards	For 2022, 2021, and 2020, the Company used the following assumptions to estimate the fair value of share-based payment awards: 2022 2021 2020 Risk-free interest rate 1.64 % - 4.35 % 0.53 % - 1.36 % 0.33 % - 1.74 % Expected dividend yield 0.00 % 0.00 % 0.00 % Expected option life (years) 6.25 6.25 6.25 Expected volatility 96 % - 101 % 96 % - 99 % 84 % - 99 %
Restricted Stock Unit Activity	The following table presents the restricted stock unit activity for the year ended December 31, 2022 : In thousands (except per share amounts) Shares Weighted Average Outstanding as of January 1, 2022 9,277 7.70 Granted 12,587 2.97 Vested ( 1,940 ) 7.30 Forfeited ( 5,463 ) 6.79 Outstanding as of December 31, 2022 14,461 $ 3.98
Stock-Based Compensation Expense Related to Option Awards	The following table presents the stock-based compensation expense related to stock-based awards for the years ended December 31, 2022, 2021, and 2020: In thousands 2022 2021 2020 Research and development $ 4,465 $ 4,327 $ 6,568 Selling, general and administrative 22,339 32,305 39,245 Restructuring ( 591 ) 306 — Stock-based compensation expense $ 26,213 $ 36,938 $ 45,813

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Reconciliation of Total Amounts of Unrecognized Tax Benefits	The following is a reconciliation of the total amounts of unrecognized tax benefits for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Beginning uncertain tax benefits $ 22,040 $ 24,034 $ 26,743 Prior year—increases — 16 2,428 Prior year—decreases ( 9,107 ) ( 2,248 ) ( 5,391 ) Current year—increases 5,782 238 254 Ending uncertain tax benefits $ 18,715 $ 22,040 $ 24,034
Jurisdictions the Company Remains Subject to Tax Examinations	The Company files income tax returns in the United States, Ireland and United Kingdom, or UK. The Company remains subject to tax examinations in the following jurisdictions as of December 31, 2022: Jurisdiction Tax Years United States—Federal 2018 - 2022 United States—State 2012 - 2022 Ireland 2018 - 2022 United Kingdom 2021 - 2022
Components of Income (Loss) from Operations Before Taxes	The components of income (loss) from operations before taxes were as follows for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 United States $ 5,358 $ 10,222 $ 14,915 Ireland and United Kingdom ( 112,527 ) ( 4,368 ) ( 32,170 ) Other 3,364 5,437 — Total (loss) / income before taxes $ ( 103,805 ) $ 11,291 $ ( 17,255 )
Benefit from Income Taxes	The provision for income taxes shown in the accompanying consolidated statements of operations consists of the following for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Current: United States—Federal $ 562 $ 2,690 $ 45 United States—State 573 716 700 Foreign 863 156 — Total current $ 1,998 $ 3,562 $ 745 Deferred: United States—Federal ( 3,721 ) 5,222 1,972 United States—State 284 ( 3,057 ) 1,956 Foreign ( 1,646 ) ( 1,619 ) ( 26,793 ) Change in valuation allowance 5,083 ( 546 ) 22,865 Total deferred $ — $ — $ — Provision for income taxes $ 1,998 $ 3,562 $ 745
Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes	The provision for income taxes differs from the amount computed by applying the statutory income tax rate to income before taxes due to the following for the years ended December 31, 2022, 2021 and 2020: In thousands 2022 2021 2020 Benefits from taxes at statutory rate $ ( 25,952 ) $ 2,823 $ ( 4,314 ) Rate differential 9,141 ( 4,416 ) 128 Change in valuation reserves 5,083 ( 546 ) 22,865 Nondeductible employee compensation 2,344 5,249 6,122 Stock option/RSU windfall (shortfall) 3,569 81 ( 3,262 ) ISO disqualifying disposition windfall — ( 219 ) ( 253 ) Research and development credits ( 958 ) ( 1,170 ) ( 6,225 ) Tax return to provision adjustments 424 ( 8,372 ) ( 138 ) Net operating loss carryback — — ( 2,465 ) Foreign exchange 7,859 4,109 ( 10,852 ) Permanent and other ( 1,542 ) 863 ( 4,283 ) Uncertain tax positions ( 3,290 ) 5,160 3,422 Foreign-derived intangible income ( 2,935 ) — — Loss of tax attributes 8,255 — — Provision for income taxes $ 1,998 $ 3,562 $ 745
Income Tax Effect of Each Type of Temporary Difference Comprising Net Deferred Tax Asset	The income tax effect of each type of temporary difference comprising the net deferred tax asset as of December 31, 2022 and 2021 is as follows: In thousands December 31, 2022 December 31, 2021 Deferred tax assets: Net operating losses $ 136,862 $ 127,378 Stock-based compensation 11,616 8,563 Tax credits 2,639 15,803 Capitalized R&D 4,723 — Lease liability 2,583 2,348 Other reserves and accrued liabilities 11,895 11,257 Gross deferred tax assets 170,318 165,349 Less: valuation allowance ( 165,378 ) ( 160,295 ) Total deferred tax assets 4,940 5,054 Deferred tax liabilities: Depreciation and amortization ( 3,337 ) ( 3,404 ) Lease asset ( 1,603 ) ( 1,639 ) Other liabilities — ( 11 ) Total deferred tax liabilities ( 4,940 ) ( 5,054 ) Net deferred tax assets $ — $ —
Valuation Allowance	The following table reflects the activity in the valuation allowance for the years ended December 31, 2022 and 2021: In thousands 2022 2021 Beginning valuation allowance $ 160,295 $ 160,841 Increase as reflected in income tax expense 12,942 2,899 Foreign exchange ( 7,859 ) ( 3,445 ) Ending valuation allowance $ 165,378 $ 160,295

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
	Dec. 31, 2022
Revenue from Contract with Customer [Abstract]
Summarize Activity of the Net Product Revenue Allowance and Reserve Categories	The following tables summarize activity in each of the net product revenue allowance and reserve categories described above for the years ended December 31, 2022 and 2021: In thousands Trade Rebates, Product Other Total Balance as of January 1, 2021 $ 36,242 $ 141,200 $ 7,798 $ 5,584 $ 190,824 Provision related to current period sales 121,378 684,010 1,531 45,501 852,420 Provision related to prior period sales — ( 2,034 ) — — ( 2,034 ) Credits/payments made for current period sales ( 36,473 ) ( 504,210 ) — ( 42,754 ) ( 583,437 ) Credits/payments made for prior period sales ( 34,511 ) ( 134,210 ) ( 1,240 ) ( 5,586 ) ( 175,547 ) Balance as of December 31, 2021 86,636 184,756 8,089 2,745 282,226 Provision related to current period sales 96,340 676,816 2,347 26,612 802,115 Provision related to prior period sales — 592 — — 592 Credits/payments made for current period sales ( 54,952 ) ( 548,783 ) — ( 24,671 ) ( 628,406 ) Credits/payments made for prior period sales ( 83,398 ) ( 177,288 ) ( 1,690 ) ( 2,630 ) ( 265,006 ) Balance as of December 31, 2022 $ 44,626 $ 136,093 $ 8,746 $ 2,056 $ 191,521

Development, Commercializatio_2

Development, Commercialization and Supply Agreements (Tables)	12 Months Ended
	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Product Approval	The Company received approval of VASCEPA under the MARINE and REDUCE-IT indications in the following countries: Country MARINE REDUCE-IT Launch Date Lebanon March 2018 August 2021 June 2018 United Arab Emirates July 2018 October 2021 February 2019 Qatar December 2019 April 2021 — Bahrain April 2021 April 2022 — Kuwait December 2021 — — Saudi Arabia March 2022 — —
Changes in Balances of Contract Assets and Liabilities and Revenues Recognized	The following table presents changes in the balances of the Company’s contract assets and liabilities for years ended December 31, 2022 and 2021: In thousands Balance at Additions Deductions Balance at Year ended December 31, 2022: Contract assets $ — $ — $ — $ — Contract liabilities: Deferred revenue $ 16,709 $ 6 $ ( 1,369 ) $ 15,346 Year ended December 31, 2021: Contract assets $ — $ — $ — $ — Contract liabilities: Deferred revenue $ 18,632 $ 128 $ ( 2,051 ) $ 16,709 During the years ended December 31, 2022 and 2021, the Company recognized the following revenues as a result of changes in the contract asset and contract liability balances in the respective periods: In thousands Twelve Months Ended December 31, Revenue recognized in the period from: 2022 2021 Amounts included in contract liability at the beginning of the period $ 1,366 $ 1,997 Performance obligations satisfied in previous periods $ 2 $ 46

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2022
Leases [Abstract]
Maturity Analysis of Undiscounted Payments for Operating Lease Liabilities and Reconciliation with Carrying Amount of Lease Liability	The table below depicts a maturity analysis of the Company’s undiscounted payments for its operating lease liabilities and their reconciliation with the carrying amount of lease liability presented in the statement of financial position as of December 31, 2022: Undiscounted 2023 $ 2,796 2024 2,572 2025 2,096 2026 2,131 2027 1,962 2028 and thereafter 5,251 Total undiscounted payments $ 16,808 Discount Adjustments $ ( 5,227 ) Current operating lease liability 1,566 Long-term operating lease liability $ 10,015

Nature of Business and Basis _2

Nature of Business and Basis of Presentation - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | Segment	1
Total assets	$ 886,179,000	$ 1,068,065,000
Cash and liquid short-term and long-term investments	310,600,000
Total current assets	689,098,000	878,727,000
Cash and cash equivalents	217,666,000	219,454,000
Short-term investments	91,695,000	234,674,000
Accounts receivable, net	130,990,000	163,653,000
Inventory	228,732,000	234,676,000
Long-term investments	1,275,000	34,996,000
Long-term inventory	163,620,000	$ 121,254,000
Debt outstanding	$ 0

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) $ in Thousands		12 Months Ended
	Aug. 19, 2022 USD ($)	Dec. 31, 2022 USD ($) Segment Customer	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 06, 2022 Sales	Sep. 22, 2021 Sales
Significant Accounting Policies [Line Items]
Trade receivables, credit period		45 days
Maturities period		24 months
Unrealized gain (loss) on held-to-maturity securities		$ (400)	$ (200)
Number of operating segments | Segment		1
Foreign currency loss		$ 700	600
Number of sales representatives | Sales					75	300
Cash expenditures		192	1,186
Restructuring and transformation initiative expense		13,526	13,717
Charges of recognized within Cost of goods sold restructuring inventory		18,078
Comprehensive Cost Reduction Plan [Member]
Significant Accounting Policies [Line Items]
Restructuring and transformation initiative expense		9,400
Charges of recognized within Cost of goods sold restructuring inventory		$ 18,100
Food and Drug Administration | Discontinued of Business Operations | DE
Significant Accounting Policies [Line Items]
Restructuring and transformation initiative expense	$ 4,200
One-time Termination Benefits | Go-to-Market Strategy
Significant Accounting Policies [Line Items]
Cash expenditures			$ 13,700
Minimum
Significant Accounting Policies [Line Items]
Trade receivables, credit period		30 days
Maximum
Significant Accounting Policies [Line Items]
Trade receivables, credit period		60 days
Foreign currency loss				$ 100
Short Term Investments
Significant Accounting Policies [Line Items]
Maturities period		12 months
Long Term Investments
Significant Accounting Policies [Line Items]
Maturities period		12 months
Money Market Instruments
Significant Accounting Policies [Line Items]
Maturities period		90 days
Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Number of customers | Customer		3
Customer A | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		35%	37%
Customer A | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		35%	39%
Customer B | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		31%	28%
Customer B | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		21%	22%
Customer C | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		27%	27%
Customer C | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage		39%	35%
Internal Revenue Service (IRS)
Significant Accounting Policies [Line Items]
Open tax year		2018
Earliest Tax Year | New Jersey Department of Treasury
Significant Accounting Policies [Line Items]
Open tax year		2012
Latest Tax Year | New Jersey Department of Treasury
Significant Accounting Policies [Line Items]
Open tax year		2015

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Impact of Accounts Receivable Reserves on Gross Trade Accounts Receivable Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross trade accounts receivable	$ 187,418	$ 262,948
Accounts receivable, net	130,990	163,653
Trade Allowances
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowances and reserves	(44,626)	(86,636)
Chargebacks
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowances and reserves	$ (11,802)	(11,714)
Allowance for Doubtful Accounts
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowances and reserves		$ (945)

Significant Accounting Polici_6

Significant Accounting Policies - Calculation of Net (Loss) Income and Number of Shares Used to Compute Basic and Diluted Net (Loss) Earnings per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
(Loss) Earnings Per Share [Line Items]
Net (loss) income -basic and diluted	$ (105,803)	$ 7,729	$ (18,000)
Weighted average shares outstanding-basic	401,155	395,992	381,759
Weighted average shares outstanding-diluted	401,155	402,480	381,759
Net (loss) earnings per share-basic	$ (0.26)	$ 0.02	$ (0.05)
Net (loss) earnings per share-diluted	$ (0.26)	$ 0.02	$ (0.05)
Stock Options
(Loss) Earnings Per Share [Line Items]
Effect of dilutive securities		4,420
Restricted Stock and Restricted Stock Units
(Loss) Earnings Per Share [Line Items]
Effect of dilutive securities		2,068

Significant Accounting Polici_7

Significant Accounting Policies - Anti-Dilutive Securities Not Included in the Computation of Net (Loss) Earnings per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	19,182	9,926	16,664
Restricted Stock and Restricted Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	14,461	3,764	7,710
Laxdale Milestone Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities		1,984

Significant Accounting Polici_8

Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Asset:
Asset, fair value	$ 192,307	$ 374,911
Level 1
Asset:
Asset, fair value	86,541	118,282
Level 2
Asset:
Asset, fair value	105,766	256,629
Money Market Fund
Asset:
Asset, fair value	81,870	95,063
Money Market Fund | Level 1
Asset:
Asset, fair value	81,870	95,063
U.S. Treasury Shares
Asset:
Asset, fair value	3,117	23,219
U.S. Treasury Shares | Level 1
Asset:
Asset, fair value	3,117	23,219
Agency Securities
Asset:
Asset, fair value	1,554
Agency Securities | Level 1
Asset:
Asset, fair value	1,554
Corporate Bonds
Asset:
Asset, fair value	28,416	83,587
Corporate Bonds | Level 2
Asset:
Asset, fair value	28,416	83,587
Commercial Paper
Asset:
Asset, fair value	62,347	121,773
Commercial Paper | Level 2
Asset:
Asset, fair value	62,347	121,773
Repo Securities
Asset:
Asset, fair value	3,250	8,000
Repo Securities | Level 2
Asset:
Asset, fair value	3,250	8,000
Asset Backed Securities
Asset:
Asset, fair value	1,260	8,816
Asset Backed Securities | Level 2
Asset:
Asset, fair value	1,260	8,816
Certificate of Deposit
Asset:
Asset, fair value	9,100	21,553
Certificate of Deposit | Level 2
Asset:
Asset, fair value	9,100	21,553
Non-US Government
Asset:
Asset, fair value	1,393	12,900
Non-US Government | Level 2
Asset:
Asset, fair value	$ 1,393	$ 12,900

Significant Accounting Polici_9

Significant Accounting Policies - Summary of Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Employee restructuring separation charges	$ 9,310	$ 13,717
Vendor contract charges	4,216
Total restructuring expense	13,526	13,717
Restructuring Inventory	18,078
Stock forfeitures	591
Total restructuring costs incurred	$ 32,195	$ 13,717

Significant Accounting Polic_10

Significant Accounting Policies - Change in Restructuring Liability Associated with the Plan (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Restructuring Reserve [Roll Forward]
Balance at December 31, 2021	$ 1,186
Costs incurred	32,195
Payments	(33,189)
Balance at December 31, 2022	$ 192

Intangible Asset - Additional I

Intangible Asset - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Intangible assets estimated weighted- average remaining useful life	8 years 1 month 6 days
Capitalized cost	$ 800
Amortization of intangible asset	$ 2,545	$ 2,270	$ 1,441

Intangible Asset - Schedule of

Intangible Asset - Schedule of Carrying Value of Intangible Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
Technology rights	$ 32,859	$ 32,081
Accumulated amortization	(11,079)	(8,534)
Intangible asset, net	$ 21,780	$ 23,547

Intangible Asset - Schedule o_2

Intangible Asset - Schedule of Estimated Future Amortization Expense (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Goodwill and Intangible Assets Disclosure [Abstract]
2022	$ 2,805
2023	2,546
2024	2,805
2025	2,805
2026	2,546
Thereafter	8,273
Intangible asset, net	$ 21,780	$ 23,547

Inventory - Schedule of Invento

Inventory - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Raw materials	$ 126,391	$ 107,695
Work in process	52,297	41,965
Finished goods	213,664	206,270
Inventory	$ 392,352	$ 355,930

Inventory - Additional Informat

Inventory - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Long-term inventory	$ 163,620	$ 121,254

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 3,346	$ 3,346
Accumulated depreciation and amortization	(2,472)	(1,921)
Property, plant and equipment, net	$ 874	1,425
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	5 years
Property, plant and equipment	$ 1,633	1,633
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	lesser of useful life or lease term
Property, plant and equipment	$ 869	869
Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 617	617
Software | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	3 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	5 years
Computer equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 227	$ 227
Computer equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	3 years
Computer equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful Life	5 years

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 0.6	$ 0.6	$ 0.6

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Payroll and payroll-related expenses	$ 20,302	$ 19,730
Sales and marketing accruals	1,672	3,563
Accrued revenue allowances	135,061	184,216
All other	35,643	45,602
Accrued expenses and other current liabilities	$ 192,678	$ 253,111

Debt - Debt from Royalty-Bearin

Debt - Debt from Royalty-Bearing Instrument-December 2012 Financing - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Debt Disclosure [Line Items]
Interest expense, non-cash	$ 635

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	Dec. 31, 2022 USD ($)	Dec. 31, 2022 GBP (£)	Jul. 13, 2022 GBP (£)	Dec. 31, 2021 USD ($)	Mar. 26, 2021 GBP (£)
Commitments And Contingencies Disclosure [Line Items]
Potential payable amount over the agreement terms based on minimum purchase obligation | $	$ 86,000
Accrued expenses and other current liabilities | $	192,678			$ 253,111
Further Indication for AMR101 | Marketing Approval In Europe
Commitments And Contingencies Disclosure [Line Items]
Potential aggregate stock or cash payment | £					£ 7,500,000
Aggregate stock or cash payment upon potential market approval | £			£ 7,500,000
Further Indication for AMR101 | Potential Marketing Approval 1
Commitments And Contingencies Disclosure [Line Items]
Aggregate stock or cash payment upon potential market approval	6,000	£ 5,000,000
Further Indication for AMR101 | Potential Marketing Approval 2
Commitments And Contingencies Disclosure [Line Items]
Aggregate stock or cash payment upon potential market approval	$ 6,000	£ 5,000,000

Equity - Common Stock - Additio

Equity - Common Stock - Additional Information (Detail) - Jul. 13, 2022 - Food and Drug Administration € in Millions	EUR (€) shares	$ / shares
Stockholders Equity Note [Line Items]
Milestone payment | €	€ 7.5
Stock issuance of shares | shares	5,817,942
Sale of stock per share | $ / shares		$ 1.41

Equity - Preferred Stock - Addi

Equity - Preferred Stock - Additional Information (Detail) - £ / shares	Dec. 31, 2022	Dec. 31, 2021
Stockholders Equity Note [Line Items]
Common stock, par value	£ 0.50	£ 0.50

Equity - Incentive Equity Award

Equity - Incentive Equity Awards - Summarizes the Aggregate Number of Stock Options And Restricted Stock Unit (Detail) - shares	Dec. 31, 2022	Dec. 31, 2021
Stockholders Equity Note [Line Items]
Outstanding Stock Options	19,182,000	18,493,000
Stock Incentive Plan 2020
Stockholders Equity Note [Line Items]
Outstanding Stock Options	19,182,111
Stock Incentive Plan 2020 | Stock Options
Stockholders Equity Note [Line Items]
% of Outstanding Shares	4%
Stock Incentive Plan 2020 | Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
% of Outstanding Shares	3%
Outstanding RSUs	14,461,050

Equity - Incentive Equity Awa_2

Equity - Incentive Equity Awards - Summary of Equity Awards Activity (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Stockholders Equity Note [Line Items]
Stock Options Issued		33,303	1,203,845
Gross Proceeds		$ 59,686	$ 2,921,000
Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
Common Shares Issued in settlement of RSUs and Performance Based RSUs Vested		1,940,371	1,203,845
Shares retained for settlement of employee tax obligations		500,064	782,917
Performance-Based RSUs
Stockholders Equity Note [Line Items]
Common Shares Issued in settlement of RSUs and Performance Based RSUs Vested	[1]		1,923,316
Shares retained for settlement of employee tax obligations			816,931
[1] Performance-based RSUs vested in connection with the achievement of certain regulatory and sales performance conditions associated with the REDUCE-IT clinical trial and subsequent revenue growth. These performance-based RSUs have fully vested as of August 2021.

Equity - Incentive Equity Awa_3

Equity - Incentive Equity Awards - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Restricted Stock Units (RSUs)
Stockholders Equity Note [Line Items]
Stock units, Granted	12,587,000
Restricted Stock Units (RSUs) | Stock Incentive Plan 2020 and 2011
Stockholders Equity Note [Line Items]
Stock units, Granted	1,597,955	218,000
Stock units, Vesting Period	3 years
Restricted Stock Units (RSUs) | Stock Incentive Plan 2020 and 2011 | Employees
Stockholders Equity Note [Line Items]
Stock units, Granted	9,069,500	5,497,700
Restricted Stock Units (RSUs) | Stock Incentive Plan 2020 and 2011 | Employees | Maximum
Stockholders Equity Note [Line Items]
Stock units, Vesting Period	4 years
Restricted Stock Units (RSUs) | Stock Incentive Plan 2020 and 2011 | Employees | Minimum
Stockholders Equity Note [Line Items]
Stock units, Vesting Period	3 years
Stock Options
Stockholders Equity Note [Line Items]
Stock units, Vesting Period	4 years
Stock Options | Stock Incentive Plan 2020 and 2011
Stockholders Equity Note [Line Items]
Stock options, additional granted	1,973,124	278,271
Stock Options | Stock Incentive Plan 2020 and 2011 | Employees
Stockholders Equity Note [Line Items]
Stock options, Granted	3,065,000	4,535,117
Stock units, Vesting Period	4 years
Performance-Based RSUs | Stock Incentive Plan 2020 and 2011 | Employees
Stockholders Equity Note [Line Items]
Stock units, Granted	1,919,500	2,008,800

Stock Incentive Plans and Sto_3

Stock Incentive Plans and Stock-Based Compensation - Additional Information (Detail)	6 Months Ended						12 Months Ended
	Nov. 30, 2022 $ / shares shares	May 31, 2022 $ / shares shares	Nov. 30, 2021 $ / shares shares	May 31, 2021 $ / shares shares	Nov. 30, 2020 $ / shares shares	May 31, 2020 $ / shares shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2020 USD ($) $ / shares	Dec. 31, 2022 £ / shares	Dec. 31, 2022 USD ($) shares	Dec. 31, 2021 £ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, par value | £ / shares										£ 0.50		£ 0.50
Weighted average fair value of the stock options granted | $ / shares							$ 2.56	$ 5.12	$ 14.43
Grant date fair value of options vested							$ 16,600,000	$ 21,100,000	$ 22,500,000
Proceeds from the exercise of options							$ 60,000	2,921,000	5,158,000
Intrinsic value of options exercised								4,900,000	9,000,000
Unrecognized stock-based compensation expense related to stock option											$ 13,500,000
Unrecognized stock-based compensation expense related to stock option, recognition period							2 years 1 month 6 days
Compensation expense related to stock option							$ 14,800,000	23,000,000	22,400,000
Compensation expense in relation to restricted stock units							$ 11,400,000	$ 13,900,000	$ 23,400,000
Ordinary shares, reserved and available for issuance | shares											15,383,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock options, Vesting Period							4 years
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense related to stock option											$ 23,700,000
Unrecognized stock-based compensation expense related to stock option, recognition period							2 years 2 months 12 days
Stock Incentive Plan 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares | shares											20,000,000
Plans | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock options, Vesting Period							4 years
Expire period							10 years
2017 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Ordinary shares, reserved and available for issuance | shares											3,000,000
Percentage of fair market value to payroll deductions to eligible employees to purchase ordinary shares							85%
Maximum fair market value of stock which can be purchased by participant in calendar year							$ 25,000
Issuance of common stock under employee stock purchase plan (in shares) | shares	191,482	265,214	172,884	226,402	223,545	123,608
Sale of stock price per share | $ / shares	$ 1.15	$ 1.45	$ 3.06	$ 3.86	$ 4.22	$ 5.83
Reserved for future issuance | shares											1,361,577
2017 Employee Stock Purchase Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of payroll deductions to eligible employees to purchase ordinary shares											15%

Stock Incentive Plans and Sto_4

Stock Incentive Plans and Stock-Based Compensation - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Number of Shares
Outstanding as of January 1, 2022	18,493,000
Granted	5,038,000
Forfeited	(4,105,000)
Expired	(211,000)
Exercised	(33,303)	(1,203,845)
Outstanding as of December 31, 2022	19,182,000	18,493,000
Exercisable as of December 31, 2022	12,888,000
Vested and expected to vest as of December 31, 2022	18,867,000
Available for future grant as of December 31, 2022	15,383,000
Weighted Average Exercise Price
Outstanding as of January 1, 2022	$ 7.32
Granted	2.56
Forfeited	8.39
Expired	11.65
Exercised	1.79
Outstanding as of December 31, 2022	5.80	$ 7.32
Exercisable as of December 31, 2022	6.80
Vested and expected to vest as of December 31, 2022	$ 5.83
Weighted Average Remaining Contractual Term
Outstanding as of December 31, 2022	6 years 2 months 12 days
Exercisable as of December 31, 2022	4 years 10 months 24 days
Vested and expected to vest as of December 31, 2022	6 years 2 months 12 days
Aggregate Intrinsic Value
Outstanding as of December 31, 2022	$ 158
Exercisable as of December 31, 2022	86
Vested and expected to vest as of December 31, 2022	$ 155

Stock Incentive Plans and Sto_5

Stock Incentive Plans and Stock-Based Compensation - Assumptions Used to Estimate Fair Value of Share-Based Payment Awards (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share-Based Payment Arrangement [Abstract]
Risk free interest rate, minimum	1.64%	0.53%	0.33%
Risk free interest rate, maximum	4.35%	1.36%	1.74%
Expected dividend yield	0%	0%	0%
Expected option life (years)	6 years 3 months	6 years 3 months	6 years 3 months
Expected volatility, minimum	96%	96%	84%
Expected volatility, maximum	101%	99%	99%

Stock Incentive Plans and Sto_6

Stock Incentive Plans and Stock-Based Compensation - Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) shares in Thousands	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Shares
Beginning Balance | shares	9,277
Granted | shares	12,587
Vested | shares	(1,940)
Forfeited | shares	(5,463)
Ending Balance | shares	14,461
Weighted Average Grant-Date Fair Value
Beginning Balance | $ / shares	$ 7.70
Granted | $ / shares	2.97
Vested | $ / shares	7.30
Forfeited | $ / shares	6.79
Ending Balance | $ / shares	$ 3.98

Stock Incentive Plans and Sto_7

Stock Incentive Plans and Stock-Based Compensation - Stock-Based Compensation Expense Related to Option Awards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 26,213	$ 36,938	$ 45,813
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,465	4,327	6,568
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	22,339	32,305	$ 39,245
Restructuring
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ (591)	$ 306

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Mar. 27, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
Total amount of unrecognized tax benefits that would affect the tax rate if recognized		$ 8,200,000	$ 7,900,000
Interest related to uncertain tax positions		500,000	900,000
Penalties related to uncertain tax positions		0	0
Gross liabilities to expire in 2023		0
Provision for income taxes		(1,998,000)	(3,562,000)	$ (745,000)
Decrease in net operating loss carryforwards from prior years		15,600,000
Tax credit carryforwards		2,639,000	15,803,000
Undistributed earning retained indefinitely for reinvestment by foreign subsidiary		0
Unrecognized deferred income tax liability		0
ASU No. 2016-09
Income Taxes [Line Items]
Provisions benefit for income taxes		600,000	100,000	3,700,000
CARES Act
Income Taxes [Line Items]
Carry back net operating losses arising beginning year	2018
Carry back net operating losses arising end year	2020
Net operating loss carryback period	5 years
Provision for income taxes		$ 0	$ 0	$ 2,500,000
Ireland
Income Taxes [Line Items]
Corporate tax rate		25%	25%	25%
Ireland | Amarin Pharmaceuticals Ireland Limited
Income Taxes [Line Items]
Corporate tax rate		12.50%	12.50%	12.50%
Ireland | Non-Trading Activity
Income Taxes [Line Items]
Corporate tax rate		25%
Ireland | Trading Activity
Income Taxes [Line Items]
Corporate tax rate		12.50%
U.S. and Non-U.S.
Income Taxes [Line Items]
Foreign net operating loss carryforwards		$ 834,400,000
U.S. Federal
Income Taxes [Line Items]
Tax credit carryforwards		$ 9,500,000
U.S. Federal | Minimum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2023
U.S. Federal | Maximum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2042
State
Income Taxes [Line Items]
Tax credit carryforwards		$ 3,700,000
State | Minimum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2023
State | Maximum
Income Taxes [Line Items]
Tax credit carryforward expiration year		2042

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Total Amounts of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Beginning uncertain tax benefits	$ 22,040	$ 24,034	$ 26,743
Prior year—increases		16	2,428
Prior year—decreases	(9,107)	(2,248)	(5,391)
Current year—increases	5,782	238	254
Ending uncertain tax benefits	$ 18,715	$ 22,040	$ 24,034

Income Taxes - Jurisdictions th

Income Taxes - Jurisdictions the Company Remains Subject to Tax Examinations (Detail)	12 Months Ended
	Dec. 31, 2022
United States | Earliest Tax Year | Federal
Income Taxes [Line Items]
Tax Years	2018
United States | Earliest Tax Year | State
Income Taxes [Line Items]
Tax Years	2012
United States | Latest Tax Year | Federal
Income Taxes [Line Items]
Tax Years	2022
United States | Latest Tax Year | State
Income Taxes [Line Items]
Tax Years	2022
Ireland | Earliest Tax Year
Income Taxes [Line Items]
Tax Years	2018
Ireland | Latest Tax Year
Income Taxes [Line Items]
Tax Years	2022
United Kingdom | Earliest Tax Year
Income Taxes [Line Items]
Tax Years	2021
United Kingdom | Latest Tax Year
Income Taxes [Line Items]
Tax Years	2022

Income Taxes - Components of In

Income Taxes - Components of Income (Loss) from Operations Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Taxes [Line Items]
United States	$ 5,358	$ 10,222	$ 14,915
(Loss) income from operations before taxes	(103,805)	11,291	(17,255)
Republic of Ireland and the United Kingdom
Income Taxes [Line Items]
(Loss) / income before taxes, Foreign	(112,527)	(4,368)	$ (32,170)
Other
Income Taxes [Line Items]
(Loss) / income before taxes, Foreign	$ 3,364	$ 5,437

Income Taxes - Benefit from Inc

Income Taxes - Benefit from Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current:
United States—Federal	$ 562	$ 2,690	$ 45
United States—State	573	716	700
Foreign	863	156
Total current	1,998	3,562	745
Deferred:
United States—Federal	(3,721)	5,222	1,972
United States—State	(284)	(3,057)	1,956
Foreign	(1,646)	(1,619)	(26,793)
Change in valuation allowance	5,083	(546)	22,865
Provision for income taxes	$ 1,998	$ 3,562	$ 745

Income Taxes - Difference betwe

Income Taxes - Difference between Benefit from Income Taxes and Amount Computed by Applying Statutory Income Tax Rate to Income Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Benefits from taxes at statutory rate	$ (25,952)	$ (2,823)	$ (4,314)
Rate differential	(9,141)	(4,416)	128
Change in valuation reserves	5,083	(546)	22,865
Nondeductible employee compensation	2,344	5,249	6,122
Stock option/RSU windfall (shortfall)	3,569	81	(3,262)
ISO disqualifying disposition windfall		(219)	(253)
Research and development credits	(958)	(1,170)	(6,225)
Tax return to provision adjustments	(424)	(8,372)	(138)
Net operating loss carryback			(2,465)
Foreign exchange	7,859	4,109	(10,852)
Permanent and other	(1,542)	863	(4,283)
Uncertain tax positions	(3,290)	5,160	3,422
Foreign-derived intangible income	(2,935)
Loss of tax attributes	8,255
Provision for income taxes	$ 1,998	$ 3,562	$ 745

Income Taxes - Income Taxes Eff

Income Taxes - Income Taxes Effect of Each Type of Temporary Difference Comprising Net Differed Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses	$ 136,862	$ 127,378
Stock-based compensation	11,616	8,563
Tax credits	2,639	15,803
Capitalized R&D	4,723
Lease liability	2,583	2,348
Other reserves and accrued liabilities	11,895	11,257
Gross deferred tax assets	170,318	165,349
Less: valuation allowance	(165,378)	(160,295)	$ (160,841)
Total deferred tax assets	4,940	5,054
Deferred tax liabilities:
Depreciation and amortization	(3,337)	(3,404)
Lease asset	(1,603)	(1,639)
Other liabilities	0	(11)
Total deferred tax liabilities	(4,940)	(5,054)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Valuation Allowa

Income Taxes - Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Beginning valuation allowance	$ 160,295	$ 160,841
Increase as reflected in income tax expense	12,942	2,899
Foreign exchange	(7,859)	(3,445)
Ending valuation allowance	$ 165,378	$ 160,295

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Retirement Benefits [Abstract]
Contributions made under defined contribution plan	$ 1.7	$ 1.9	$ 1.7

Co-Promotion Agreement - Additi

Co-Promotion Agreement - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2018	Dec. 31, 2021
Co Promotion Agreement [Line Items]
Accrued expenses and other current liabilities	$ 192,678		$ 253,111
Co-Promotion Agreement | Kowa Pharmaceuticals America, Inc.
Co Promotion Agreement [Line Items]
Promotion fee as a percentage of gross margin		18.50%
Maximum co-promotion tail payments receive period	3 years
Co-promotion tail payments payable		$ 17,800
Accrued co- promotion tail payments		$ 16,600
Accrued expenses and other current liabilities			$ 600

Revenue Recognition - Additiona

Revenue Recognition - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022
Disaggregation Of Revenue [Line Items]
Payment period from distributors received from date of sale	45 days
Effect of significant financing component when transfer and customer payment of good or service occurs within one year or less	true
VASCEPA 1-Gram
Disaggregation Of Revenue [Line Items]
Product expiration date after being converted into capsule form	4 years
VASCEPA 0.5-Gram
Disaggregation Of Revenue [Line Items]
Product expiration date after being converted into capsule form	3 years
Minimum
Disaggregation Of Revenue [Line Items]
Payment period from distributors received from date of sale	30 days
Sales discount percentage	2%
Maximum
Disaggregation Of Revenue [Line Items]
Payment period from distributors received from date of sale	60 days
Sales discount percentage	3%

Revenue Recognition - Summarize

Revenue Recognition - Summarize Activity of the Net Product Revenue Allowance and Reserve Categories (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 282,226	$ 190,824
Provision related to current period sales	802,115	852,420
Provision related to prior period sales	592	(2,034)
Credits/payments made for current period sales	(628,406)	(583,437)
Credits/payments made for prior period sales	(265,006)	(175,547)
Ending balance	191,521	282,226
Trade Allowances
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning balance	86,636	36,242
Provision related to current period sales	96,340	121,378
Credits/payments made for current period sales	(54,952)	(36,473)
Credits/payments made for prior period sales	(83,398)	(34,511)
Ending balance	44,626	86,636
Rebates, Chargebacks and Discounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning balance	184,756	141,200
Provision related to current period sales	676,816	684,010
Provision related to prior period sales	592	(2,034)
Credits/payments made for current period sales	(548,783)	(504,210)
Credits/payments made for prior period sales	(177,288)	(134,210)
Ending balance	136,093	184,756
Product Returns
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning balance	8,089	7,798
Provision related to current period sales	2,347	1,531
Credits/payments made for prior period sales	(1,690)	(1,240)
Ending balance	8,746	8,089
Other Incentives
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,745	5,584
Provision related to current period sales	26,612	45,501
Credits/payments made for current period sales	(24,671)	(42,754)
Credits/payments made for prior period sales	(2,630)	(5,586)
Ending balance	$ 2,056	$ 2,745

Development, Commercializatio_3

Development, Commercialization and Supply Agreement - Additional Information (Detail)

1 Months Ended

12 Months Ended

Jan. 31, 2022 USD ($)

Jan. 31, 2021 USD ($)

Feb. 29, 2020 USD ($)

Jan. 31, 2020 USD ($)

Sep. 30, 2018 USD ($)

Sep. 30, 2017 USD ($)

Mar. 31, 2016 USD ($)

Feb. 28, 2015 USD ($)

Dec. 31, 2022 USD ($) Item

Dec. 31, 2021 USD ($)

Dec. 31, 2020 USD ($)

Dec. 31, 2018 USD ($)

Feb. 28, 2023 USD ($)

License And Collaboration Agreements [Line Items]

Revenue recognized related to upfront and milestone payments

$ 1,369,000

$ 2,051,000

Licenses revenue

369,193,000

583,187,000

$ 614,060,000

Deferred revenue

15,346,000

16,709,000

18,632,000

Product Revenue, Net

License And Collaboration Agreements [Line Items]

Licenses revenue

$ 366,511,000

580,320,000

$ 607,025,000

Mochida Pharmaceutical Co., Ltd. | In-licenses

License And Collaboration Agreements [Line Items]

Milestones payment

$ 1,000,000

$ 1,000,000

Mochida Pharmaceutical Co., Ltd. | In-licenses | Research and Development Expense

License And Collaboration Agreements [Line Items]

Upfront payment

$ 2,700,000

Edding | Out-licenses

License And Collaboration Agreements [Line Items]

Non-refundable up-front received

$ 15,000,000

Number of indications of the regulatory milestone events relating to the submission and approval | Item

3

Amounts to be received upon achievement of the regulatory milestone events

$ 33,000,000

Sales-based milestone event payment

120,000,000

Revenue recognized related to upfront and milestone payments

600,000

1,100,000

Deferred revenue

9,300,000

9,800,000

Edding | Out-licenses | Licensing Revenue

License And Collaboration Agreements [Line Items]

Licenses revenue

7,700,000

7,100,000

Edding | Out-licenses | Product Revenue, Net

License And Collaboration Agreements [Line Items]

Licenses revenue

200,000

300,000

Edding | Out-licenses | Maximum

License And Collaboration Agreements [Line Items]

Additional upfront payment eligible to receive based on development, regulatory and sales Milestone

153,000,000

Amounts to be received upon achievement of the regulatory milestone events

15,000,000

Sales-based milestone event payment

50,000,000

Edding | Out-licenses | Minimum

License And Collaboration Agreements [Line Items]

Amounts to be received upon achievement of the regulatory milestone events

2,000,000

Sales-based milestone event payment

5,000,000

Edding | Out-licenses | Clinical Trial Application

License And Collaboration Agreements [Line Items]

Non-refundable milestone payment received

$ 1,000,000

Biologix FZCo | Out-licenses

License And Collaboration Agreements [Line Items]

Revenue recognition period of non-refundable up-front payment

10 years

Biologix FZCo | Out-licenses | Product Revenue, Net

License And Collaboration Agreements [Line Items]

Licenses revenue

1,000,000

1,400,000

HLS | Out-licenses

License And Collaboration Agreements [Line Items]

Non-refundable up-front received

$ 5,000,000

Non-refundable milestone payment received

$ 2,500,000

$ 3,800,000

$ 2,500,000

Revenue recognized related to upfront and milestone payments

700,000

900,000

Deferred revenue

5,600,000

6,200,000

Non-refundable up-front received period

6 months

Non-refundable milestone payment received

$ 3,800,000

HLS | Out-licenses | Health Canada

License And Collaboration Agreements [Line Items]

Non-refundable milestone payment received

2,500,000

HLS | Out-licenses | Licensing Revenue

License And Collaboration Agreements [Line Items]

Licenses revenue

8,200,000

7,500,000

HLS | Out-licenses | Product Revenue, Net

License And Collaboration Agreements [Line Items]

Licenses revenue

$ 2,900,000

$ 0

HLS | Out-licenses | Maximum

License And Collaboration Agreements [Line Items]

Additional upfront payment eligible to receive based on development, regulatory and sales Milestone

50,000,000

HLS | Out-licenses | Achievement of REDUCE-IT Trial

License And Collaboration Agreements [Line Items]

Non-refundable milestone payment received

$ 2,500,000

CSL Seqirus | Out-licenses | Subsequent Event

License And Collaboration Agreements [Line Items]

Upfront payment receivable

$ 500,000

Event-related milestone payments receivable

8,000,000

Additional product-related milestone payments receivable

$ 4,000,000

Development, Commercializatio_4

Development, Commercialization and Supply Agreement - Additional Information (Detail 1) - Out-licenses - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-01-01	Dec. 31, 2022
Edding
License And Collaboration Agreements [Line Items]
Revenue recognized over remaining period	12 years
HLS
License And Collaboration Agreements [Line Items]
Revenue recognized over remaining period	8 years

Development, Commercializatio_5

Development, Commercialization and Supply Agreement - Summary of Product Approval (Detail) - Biologix FZCo - Out-licenses - VASCEPA	12 Months Ended
	Dec. 31, 2022
Lebanon
License And Collaboration Agreements [Line Items]
Launch Date	2018-06
United Arab Emirates
License And Collaboration Agreements [Line Items]
Launch Date	2019-02
MARINE | Lebanon
License And Collaboration Agreements [Line Items]
Approval Date	2018-03
MARINE | United Arab Emirates
License And Collaboration Agreements [Line Items]
Approval Date	2018-07
MARINE | Qatar
License And Collaboration Agreements [Line Items]
Approval Date	2019-12
MARINE | Bahrain
License And Collaboration Agreements [Line Items]
Approval Date	2021-04
MARINE | Kuwait
License And Collaboration Agreements [Line Items]
Approval Date	2021-12
MARINE | Saudi Arabia
License And Collaboration Agreements [Line Items]
Approval Date	2022-03
REDUCE-IT | Lebanon
License And Collaboration Agreements [Line Items]
Approval Date	2021-08
REDUCE-IT | United Arab Emirates
License And Collaboration Agreements [Line Items]
Approval Date	2021-10
REDUCE-IT | Qatar
License And Collaboration Agreements [Line Items]
Approval Date	2021-04
REDUCE-IT | Bahrain
License And Collaboration Agreements [Line Items]
Approval Date	2022-04

Development, Commercializatio_6

Development, Commercialization and Supply Agreement - Changes in Balances of Contract Assets and Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Contract liabilities:
Deferred revenue, Balance at Beginning of Period	$ 16,709	$ 18,632
Deferred revenue, Additions	6	128
Deferred revenue, Deductions	(1,369)	(2,051)
Deferred revenue, Balance at End of Period	$ 15,346	$ 16,709

Development, Commercializatio_7

Development, Commercialization and Supply Agreement - Recognized Revenues Changes in Contract Asset and Contract Liability Balances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$ 1,366	$ 1,997
Performance obligations satisfied in previous periods	$ 2	$ 46

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands					12 Months Ended
	Feb. 01, 2023 USD ($)	Oct. 01, 2022 USD ($)	Feb. 01, 2022 USD ($) RenewalOption	Aug. 15, 2019 USD ($) RenewalOption	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Lessee Lease Description [Line Items]
Incremental borrowing rate for purposes of calculation of lease liabilities					11.50%
Change in incremental borrowing rate					1%
Rent payment					$ 16,808
Operating lease liability					11,600	$ 10,300
Operating lease right-of-use asset					9,074	7,660
Operating lease expense					$ 2,800	$ 2,200	$ 1,600
Bridgewater
Lessee Lease Description [Line Items]
Lease commencement date				Aug. 15, 2019
Lease agreement term				11 years
Number of renewal options | RenewalOption				2
Lease renewal term				5 years
Description of lease agreement					Amarin will have a one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date upon advance written notice and a termination payment specified in the Lease.
Lease termination description					one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date
Lease termination existence of option to extend				true
Rent payment				$ 100
Bridgewater | Subsequent Event
Lessee Lease Description [Line Items]
Sublease commencement date	Feb. 01, 2023
Lease agreement term	7 years 6 months
Receive rent payment	$ 100
Zug Switzerland
Lessee Lease Description [Line Items]
Lease commencement date			Feb. 01, 2022
Lease agreement term			5 years
Number of renewal options | RenewalOption			1
Lease renewal term			5 years
Rent payment			$ 200
Dublin
Lessee Lease Description [Line Items]
Lease commencement date		Oct. 01, 2022
Lease agreement term		2 years
Rent payment		$ 400
Maximum
Lessee Lease Description [Line Items]
Short term lease period					12 months
Maximum | Vehicles
Lessee Lease Description [Line Items]
Lease agreement term					36 months

Leases - Maturity Analysis of U

Leases - Maturity Analysis of Undiscounted Payments for Operating Lease Liabilities and Reconciliation with Carrying Amount of Lease Liability (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Undiscounted lease payments
2023	$ 2,796
2024	2,572
2025	2,096
2026	2,131
2027	1,962
2028 and thereafter	5,251
Total undiscounted payments	16,808
Discount Adjustments	(5,227)
Current operating lease liability	$ 1,566
Operating lease, liability, current, statement of financial position [Extensible List]	Accrued expenses and other current liabilities
Long-term operating lease liability	$ 10,015	$ 8,576