Nature of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2019
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 with expertise in omega-3 fatty acids and lipid science focused on the commercialization and development of therapeutics to improve cardiovascular health and reduce cardiovascular risk. The Company’s lead product, Vascepa^® (icosapent ethyl), was first approved by the U.S. Food and Drug Administration, or 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. On December 13, 2019, the FDA approved a new indication and label expansion for Vascepa based on the landmark results of our cardiovascular outcomes trial, REDUCE-IT^®, or Reduction of Cardiovascular Events with EPA – Intervention Trial. Vascepa is the first and only drug approved by the FDA as an adjunct to maximally tolerated statin therapy for reducing persistent cardiovascular risk in select high risk patients. Vascepa is available in the United States, or the U.S., by prescription only. In January 2013, the Company began selling and marketing 1-gram size Vascepa capsules in the United States, and in October 2016, introduced a smaller 0.5-gram capsule size. The Company, since inception, has devoted substantial resources to research and development efforts, most significantly, the development and conduct of a long-term cardiovascular outcomes study of Vascepa, REDUCE-IT. The Company announced topline results from REDUCE-IT on September 24, 2018. On November 10, 2018, the Company presented primary results of REDUCE-IT at the 2018 Scientific Sessions of the American Heart Association, or AHA, and the results were concurrently published in The New England Journal of Medicine. REDUCE-IT met its primary endpoint demonstrating a 25% relative risk reduction, or RRR, to a high degree of statistical significance (p<0.001), in first occurrence of major adverse cardiovascular events, or MACE, in the intent-to-treat patient population with use of Vascepa 4 grams/day as compared to placebo. REDUCE-IT also showed a 26% RRR in its key secondary composite endpoint of cardiovascular death, heart attacks and stroke (p<0.001). On March 18, 2019, the Company publicly presented the total cardiovascular events results, and the method of calculating such events, of the REDUCE-IT study at the American College of Cardiology’s, or ACC, 68th Annual Scientific Session and such results and methods were concurrently published in the Journal of the American College of Cardiology. The FDA granted Priority Review designation to the Company’s March 2019 supplemental new drug application, or sNDA, seeking an expanded indication for Vascepa in the United States based on the positive results of the REDUCE-IT study. In November 2019, the FDA held an Endocrinologic and Metabolic Drugs Advisory Committee, or EMDAC, meeting to review the REDUCE-IT sNDA. The EMDAC voted unanimously (16-0) to recommend approval of an indication and label expansion for Vascepa to reduce cardiovascular events in high-risk patients based on the REDUCE-IT results. On December 13, 2019, the FDA approved a new indication and related label expansion based on REDUCE-IT. In the United States, the Company sells Vascepa principally to a limited number of major wholesalers, as well as selected regional wholesalers and specialty pharmacy providers, or collectively, its distributors or its customers, that in turn resell Vascepa to retail pharmacies for subsequent resale to patients and healthcare providers. The Company markets Vascepa in the United States through its direct sales force. Prior to the REDUCE-IT results topline announcement in September 2018, our commercialization of Vascepa was somewhat limited. Subsequent to learning the positive cardiovascular outcomes results of the REDUCE-IT study, we have increased our promotional efforts. Based on the positive REDUCE-IT results, in early 2019, we increased the size of our sales force to approximately 440 sales professionals, including approximately 400 sales representatives. As a result of the FDA’s newly approved indication and label expansion, we are close to completing the expansion of our direct sales force to approximately 900 sales professionals, including 800 sales representatives, which is expected to be completed in early 2020. Most of the expanded sales management team needed to support this sales force expansion was hired, or internally promoted, and trained prior to December 31, 2019. In addition to promotion of Vascepa in the United States, based on REDUCE-IT, we have increased focus on expansion of our development efforts for Vascepa to major markets outside the United States. We currently have strategic collaborations to develop and commercialize Vascepa in select territories outside the United States. 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, 2019, 2018 and 2017 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. Certain prior year balances related to beginning and ending cash and cash equivalents and restricted cash in the consolidated statements of cash flows have been conformed to the current year presentation. 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. At December 31, 2019, the Company had Current assets of $855.0 million, including Cash and cash equivalents of $644.6 million, Accounts receivable, net, of $116.4 million and Inventory of $76.8 million. The Company’s consolidated balance sheet at December 31, 2019 also includes a royalty-bearing instrument which is expected to be fully paid during 2020 based on the percentage of Vascepa net revenues calculated quarterly. As of December 31, 2019, the Company had no other debt outstanding.

Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2019

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 with expertise in omega-3 fatty acids and lipid science focused on the commercialization and development of therapeutics to improve cardiovascular health and reduce cardiovascular risk. The Company’s lead product, Vascepa^® (icosapent ethyl), was first approved by the U.S. Food and Drug Administration, or 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. On December 13, 2019, the FDA approved a new indication and label expansion for Vascepa based on the landmark results of our cardiovascular outcomes trial, REDUCE-IT^®, or Reduction of Cardiovascular Events with EPA – Intervention Trial. Vascepa is the first and only drug approved by the FDA as an adjunct to maximally tolerated statin therapy for reducing persistent cardiovascular risk in select high risk patients. Vascepa is available in the United States, or the U.S., by prescription only. In January 2013, the Company began selling and marketing 1-gram size Vascepa capsules in the United States, and in October 2016, introduced a smaller 0.5-gram capsule size.

The Company, since inception, has devoted substantial resources to research and development efforts, most significantly, the development and conduct of a long-term cardiovascular outcomes study of Vascepa, REDUCE-IT. The Company announced topline results from REDUCE-IT on September 24, 2018. On November 10, 2018, the Company presented primary results of REDUCE-IT at the 2018 Scientific Sessions of the American Heart Association, or AHA, and the results were concurrently published in The New England Journal of Medicine. REDUCE-IT met its primary endpoint demonstrating a 25% relative risk reduction, or RRR, to a high degree of statistical significance (p<0.001), in first occurrence of major adverse cardiovascular events, or MACE, in the intent-to-treat patient population with use of Vascepa 4 grams/day as compared to placebo. REDUCE-IT also showed a 26% RRR in its key secondary composite endpoint of cardiovascular death, heart attacks and stroke (p<0.001). On March 18, 2019, the Company publicly presented the total cardiovascular events results, and the method of calculating such events, of the REDUCE-IT study at the American College of Cardiology’s, or ACC, 68th Annual Scientific Session and such results and methods were concurrently published in the Journal of the American College of Cardiology.

The FDA granted Priority Review designation to the Company’s March 2019 supplemental new drug application, or sNDA, seeking an expanded indication for Vascepa in the United States based on the positive results of the REDUCE-IT study. In November 2019, the FDA held an Endocrinologic and Metabolic Drugs Advisory Committee, or EMDAC, meeting to review the REDUCE-IT sNDA. The EMDAC voted unanimously (16-0) to recommend approval of an indication and label expansion for Vascepa to reduce cardiovascular events in high-risk patients based on the REDUCE-IT results. On December 13, 2019, the FDA approved a new indication and related label expansion based on REDUCE-IT.

In the United States, the Company sells Vascepa principally to a limited number of major wholesalers, as well as selected regional wholesalers and specialty pharmacy providers, or collectively, its distributors or its customers, that in turn resell Vascepa to retail pharmacies for subsequent resale to patients and healthcare providers. The Company markets Vascepa in the United States through its direct sales force. Prior to the REDUCE-IT results topline announcement in September 2018, our commercialization of Vascepa was somewhat limited. Subsequent to learning the positive cardiovascular outcomes results of the REDUCE-IT study, we have increased our promotional efforts. Based on the positive REDUCE-IT results, in early 2019, we increased the size of our sales force to approximately 440 sales professionals, including approximately 400 sales representatives. As a result of the FDA’s newly approved indication and label expansion, we are close to completing the expansion of our direct sales force to approximately 900 sales professionals, including 800 sales representatives, which is expected to be completed in early 2020. Most of the expanded sales management team needed to support this sales force expansion was hired, or internally promoted, and trained prior to December 31, 2019. In addition to promotion of Vascepa in the United States, based on REDUCE-IT, we have increased focus on expansion of our development efforts for Vascepa to major markets outside the United States. We currently have strategic collaborations to develop and commercialize Vascepa in select territories outside the United States. 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, 2019, 2018 and 2017 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. Certain prior year balances related to beginning and ending cash and cash equivalents and restricted cash in the consolidated statements of cash flows have been conformed to the current year presentation. 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.

At December 31, 2019, the Company had Current assets of $855.0 million, including Cash and cash equivalents of $644.6 million, Accounts receivable, net, of $116.4 million and Inventory of $76.8 million. The Company’s consolidated balance sheet at December 31, 2019 also includes a royalty-bearing instrument which is expected to be fully paid during 2020 based on the percentage of Vascepa net revenues calculated quarterly. As of December 31, 2019, the Company had no other debt outstanding.