Amarin Reports Record Fourth Quarter and Full Year 2016 Financial Results and Provides Update on Operations $130.1 Million and $38.7 Million Total Revenue for Full Year and Fourth Quarter 2016 Reflect Increases of 59% an

Amarin Reports Record Fourth Quarter and Full Year 2016 Financial Results

and Provides Update on Operations

$130.1 Million and $38.7 Million Total Revenue for Full Year and Fourth Quarter 2016 Reflect Increases

of 59% and 45% Compared to Corresponding Periods in 2015

REDUCE-IT Cardiovascular Outcomes Study Remains on Schedule to Reach Onset of Final Target

Event Near the End of 2017

Management to Host Conference Call at 7:30 a.m. ET Today

BEDMINSTER, N.J., and DUBLIN, Ireland, February 28, 2017 Amarin Corporation plc (NASDAQ: AMRN), a biopharmaceutical company focused on the

commercialization and development of therapeutics to improve cardiovascular health, today announced financial results for the quarter and year ended December 31, 2016, and provided an update on company operations.

Key Amarin achievements in 2016 include:

2016 was another exceptional year of progress for Amarin both commercially and operationally, commented John F. Thero, president and chief

executive officer. We begin 2017 with a strong team of motivated people, a product in Vascepa that has a positively differentiated efficacy and safety profile, and managed care coverage for Vascepa that was broad at the start of 2016 and

expanded further over the past year. We are pleased to observe key opinion leaders increasing their attention to the potential impacts on public health and the practice of medicine if REDUCE-IT achieves the

results we seek and we, of course, look forward to learning the results of this landmark study.

During the fourth quarter, Amarin continued to see substantial prescription growth and steady increases in prescription

omega-3 and non-statin market share, particularly among detailed physicians. Vascepa growth continues to be driven by focused message delivery, compelling supportive data and improved managed care coverage.

Amarin reported a 45% increase in net product revenue during Q4 2016 compared to Q4 2015, which was mostly driven by prescription growth as the net price

of Vascepa has remained relatively flat. The majority of this prescription growth has come from physicians called upon and educated about Vascepa by our sales force. Based on data provided by Symphony Health Solutions and IMS Health, estimated

normalized Vascepa prescriptions totaled approximately 286,000 and 312,000, respectively, for the three months ended December 31, 2016. These prescription levels represent growth of approximately 50% and 54%, respectively, from levels in the

corresponding prior year periods.

REDUCE-IT Trial Progressing on Schedule

The REDUCE-IT cardiovascular outcomes trial continues to progress on schedule. Amarin expects the onset of the final

primary cardiovascular event to occur near the end of 2017 with report of top-line results and publications anticipated in 2018. The projected timing of available data from which we can report top-line results should be easier to estimate after the interim look which, as discussed below, is

scheduled for Q3 2017. Currently we estimate that results of the trial will become available to Amarin and be publicly communicated in mid-2018. This

estimated timing reflects our assumptions of the time necessary to collect vital data from all patients in the study, compile the results, and subject the results to scrutiny of the independent review committees and the REDUCE-IT operational team.

The 8,175-patient outcomes study is evaluating

whether treatment with Vascepa reduces cardiovascular events in patients who despite stabilized statin therapy have elevated triglyceride levels and other cardiovascular risk factors. The results of this important trial, if successful, could lead to

improved medical care for tens of millions of patients. Amarin is positioned to be the first company to complete an outcomes study in the population of patients being studied in REDUCE-IT.

The primary endpoint of this global, double-blind study is the time to the first occurrence of a composite of major adverse cardiovascular events (MACE).

Results will be compared between the Vascepa and placebo groups. The study is being conducted under a Special Protocol Assessment (SPA) agreement with the FDA.

A second pre-specified interim efficacy and safety analysis of REDUCE-IT is

scheduled to be conducted by the independent DMC at approximately 80% of the total 1,612 primary cardiovascular events targeted for completion of the study. Amarin anticipates that the onset of 80% of the target primary events will be reached in the

first half of 2017 and that the interim analysis will be conducted before the end of Q3 2017. Consistent with the trial design, Amarin continues to believe that the REDUCE-IT study is most likely to continue

to completion of 100% of the target events. This is the case because the efficacy requirements detailed to the DMC for early study stoppage after the 80% interim assessment are high and include robustness thresholds for underlying data that go

beyond the assessment for statistical significance on the analysis of the primary endpoint after the expected completion of the study at 100% of planned events.

Amarin will remain blinded to results of the REDUCE-IT study until after the study is stopped and the database is

locked at either the 80% interim analysis or at the final analysis.

Net product revenue for the three months ended December 31, 2016 and 2015 was $38.4 million and $26.4 million, respectively. Net product revenue

for the years ended December 31, 2016 and 2015 was $129.0 million and $81.0 million, respectively. These increases in net product revenue were primarily attributable to increases both in new and recurring prescriptions of Vascepa

driven by increased sales productivity.

In addition, Amarin recognized licensing revenue of $1.1 million and $0.8 million for the years ended

December 31, 2016 and 2015, respectively, related to agreements for the commercialization of Vascepa outside the United States. Amarin s partners for China and for the Middle East and North Africa are working towards regulatory approval of

Vascepa in their respective territories.

Cost of goods sold for the three months ended December 31, 2016 and 2015 was $10.2 million and

$8.4 million, respectively. Cost of goods sold for the years ended December 31, 2016 and 2015 was $34.4 million and $27.9 million, respectively. Gross margin on product sales improved to 74% and 73% in the

quarter and year ended December 31, 2016, respectively, as compared to 68% and 66% in the quarter and year ended December 31, 2015, respectively. The improvement in gross margin on

product sales was primarily driven by lower active pharmaceutical ingredient cost.

Selling, general and administrative (SG&A) expenses for the three

months ended December 31, 2016 and 2015 were $31.2 million and $23.5 million, respectively. SG&A expenses in the years ended December 31, 2016 and 2015 were $111.4 million and $101.0 million, respectively. The

increase in SG&A expenses primarily reflects an increase in sales and marketing expenses and co-promotion fees payable to Kowa Pharmaceuticals America, Inc.

Research and development expenses for the three months ended December 31, 2016 and 2015 were $10.2 million and $13.3 million, respectively.

Research and development expenses in the years ended December 31, 2016 and 2015 were $50.0 million and $51.1 million, respectively. This slight decrease was primarily driven by a decrease in overhead costs and non-cash stock based compensation.

Amarin reported a net loss applicable to common shareholders of $27.5 million

in the fourth quarter of 2016, or basic and diluted loss per share of $0.10. This net loss included $3.2 million in non-cash stock-based compensation expense and a provision for income taxes of

$12.3 million, the majority of which is non-cash. Amarin reported a net loss applicable to common shareholders of $21.9 million in the fourth quarter of 2015, or basic and diluted loss per share of

$0.12. This net loss included $3.7 million in non-cash stock-based compensation expense, a $0.7 million non-cash loss on the change in fair value of

derivatives, a $1.3 million non-cash gain on extinguishment of debt, and a benefit from income taxes of $1.5 million.

Amarin reported a net loss applicable to common shareholders of $86.4 million in the year ended December 31, 2016, or basic and diluted loss per

share of $0.41. This net loss included $13.6 million in non-cash stock-based compensation expense, an $8.2 million non-cash gain on the change in fair value of

derivatives, and a provision for income taxes of $10.0 million, the majority of which is non-cash. For the year ended December 31, 2015, Amarin reported a net loss applicable to common shareholders

of $149.1 million, or basic and diluted loss per share of $0.83. This net loss included $13.9 million in non-cash stock-based compensation expense, a $1.1 million

non-cash loss on the change in fair value of derivatives, a $1.3 million non-cash gain on extinguishment of debt, $33.9 million in charges for non-cash deemed dividends for accounting purposes, and a benefit from income taxes of $3.1 million.

reported cash and cash equivalents of $98.3 million at December 31, 2016. The cash balance includes $64.6 million in net proceeds from an equity financing completed in August. The primary purpose of that financing was to fund REDUCE-IT to completion. During the quarter ended December 31, 2016, net cash used in operating activities, including research and development costs, was $19.3 million, or approximately $3.3 million

excluding research and development costs, interest and royalties. At December 31, 2016, the company had $20.0 million in net accounts receivable ($24.1 million in gross accounts receivable before allowances and reserves) and

$20.5 million in inventory.

In January 2017, Amarin issued $30.0 million in aggregate principal amount of 3.50% Exchangeable Senior Notes due

2047 (the 2017 Notes ), and purchased approximately $15.0 million aggregate principal amount of 3.50% Exchangeable Senior Notes due 2032 that were issued in 2012 (the 2012

Notes ). Amarin was required by the terms of the indenture governing the 2012 Notes to purchase all 2012 Notes surrendered to it on January 19, 2017. Amarin has initiated the process to

redeem the remaining $0.1 million of outstanding principal amount of 2012 Notes not surrendered, which is expected to be completed in the first quarter of 2017. The remainder of the net proceeds from the 2017 Notes will be used for general

corporate and working capital purposes. Pursuant to this January 2017 debt restructuring, on a pro forma basis as of December 31, 2016, Amarin had approximately $112 million in cash and cash equivalents and $30.1 million in

exchangeable debt outstanding.

As of December 31, 2016, Amarin had approximately 269.4 million American Depositary Shares (ADSs) and ordinary

shares outstanding, 32.8 million share equivalents Series A Convertible Preferred Shares outstanding, approximately 21.2 million equivalent shares underlying stock options at a weighted-average exercise price of $3.37, and

10.1 million equivalent shares underlying restricted or deferred stock units.

Conference call and webcast information

Amarin will host a conference call at 7:30 a.m. ET today, February 28, 2017. The call will be webcast live with slides and

accessible through the investor relations section of the company s website at www.amarincorp.com, or via telephone by dialing 877-407-8033 within the United States

or 201-689-8033 from outside the United States. A replay of the call will be made available for a period of two weeks following the conference call. To hear the replay,

dial 877-481-4010 (inside the United States) or 919-882-2331 (outside the United States)

and use replay ID 10260.

Corporation plc is a biopharmaceutical company focused on the commercialization and development of therapeutics to improve cardiovascular health. Amarin s product development program leverages its extensive experience in lipid science and the

potential therapeutic benefits of polyunsaturated fatty acids. Amarin s clinical program includes a commitment to an ongoing outcomes study. Vascepa (icosapent ethyl), Amarin s

first FDA approved product, is a highly-pure, omega-3 fatty acid product available by prescription. For more information about Vascepa visit www.vascepa.com. For more information about Amarin visit

About VASCEPA (icosapent ethyl) capsules

VASCEPA (icosapent ethyl) capsules are a single-molecule prescription product consisting of 1-gram or 0.5-gram of the omega-3 acid commonly known as EPA in ethyl-ester form. Vascepa is not fish oil, but is derived from fish

through a stringent and complex FDA-regulated manufacturing process designed to effectively eliminate impurities and isolate and protect the single molecule active ingredient. Vascepa is known in scientific

literature as AMR101.

FDA-approved Indication and Usage

Important Safety Information for VASCEPA

FULL VASCEPA PRESCRIBING INFORMATION CAN BE FOUND AT WWW.VASCEPA.COM.

Vascepa has been approved for use by the United States Food and Drug Administration (FDA) as an adjunct to diet to reduce triglyceride levels in adult

patients with severe ( 500 mg/dL) hypertriglyceridemia. Vascepa is under various stages of development for potential use in other indications that have not been approved by the FDA. Nothing in this press

release should be construed as promoting the use of Vascepa in any indication that has not been approved by the FDA.

Forward-looking statements

This press release contains forward-looking statements, including statements about the future commercialization of Vascepa; expectations regarding

planned research and development expenses and increased supply purchases; expectations regarding Vascepa sales, revenue, costs and other financial metrics; expectations related to Amarin s anticipated financial performance; expectations for

event rates, interim data reviews, results and related announcements with respect to Amarin s REDUCE-IT cardiovascular outcomes study; expectations related to the interim and final outcome of the REDUCE-IT study and the anticipated successful completion of the REDUCE-IT study; and statements regarding the potential efficacy, safety and therapeutic benefits of Vascepa.

These forward-looking statements are not promises or guarantees and involve substantial risks and uncertainties. In particular, as disclosed in filings with the U.S. Securities and Exchange Commission, these risks and uncertainties include the

following: Amarin s ability to commercialize Vascepa in line with company expectations will depend in part on its ability to continue to create market demand for Vascepa through education, marketing and sales activities, to achieve continued

market acceptance of Vascepa, to continue to receive adequate levels of reimbursement from third-party payers, to continue to develop and maintain a consistent source of commercial supply at a competitive price, to comply with legal and regulatory