Amarin Reports First Quarter 2017 Financial Results and Provides Update on Operations Prescription Growth Up 50%; Outcomes Study Beyond 80% Complete Re-affirms Guidance on Full Year Net Product Revenues of between $155 a

Amarin Reports First Quarter 2017 Financial Results

and Provides Update on Operations

Prescription Growth Up >50%; Outcomes Study Beyond 80% Complete

Re-affirms Guidance on Full Year Net Product Revenues of between $155 and $165 Million

Management to Host Conference Call at 8:00 a.m. ET Today

BEDMINSTER, N.J., and DUBLIN, Ireland, May 3, 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 three months ended March 31, 2017, and provided an update on company operations.

Key Amarin achievements through March 31, 2017 include:

Historically, Q1 has been our most challenging quarter for revenue growth due to seasonal factors. We are

pleased that both revenues and prescriptions for Vascepa grew significantly in Q1, as prescription growth exceeded our internal projections. We are on-track to achieve our full year 2017 product revenue

guidance of $155 to $165 million, stated John F. Thero, president and chief executive officer. Our expectations are that REDUCE-IT study results will be reported in mid-2018, and we are actively planning for expanded promotion based on anticipated positive results from this study. There is a large unmet medical need that we are seeking to address through demonstration of

positive results in REDUCE-IT. We believe the efficacy, safety, oral administration and affordable cost of Vascepa position the product for substantial growth, assuming that

REDUCE-IT results are positive.

Increases in New and Recurring Prescriptions Drive Steady Commercial

During the first quarter, Amarin again experienced substantial prescription growth and continued increase in Vascepa market share,

particularly among detailed physicians. Overall, approximately 150,000 patients received prescriptions for Vascepa during the quarter, with new prescriptions growing to approximately 5% of the non-statin lipid

modifying market and approaching 30% of the prescription omega-3 market. Strong Vascepa growth is driven by positive physician experience in conjunction with our focused message delivery, compelling efficacy

and safety data, and improved managed care coverage.

Estimated normalized total Vascepa prescriptions, based on data from Symphony Health Solutions and

IMS Health, totaled approximately 305,000 and 335,000, respectively, for the three months ended March 31, 2017. These prescription levels represent growth of approximately 52% and 58%, respectively, from prior year levels.

During the first quarter of 2017, overall wholesaler inventory levels decreased from year-end 2016 levels calculated

based on estimated days of Vascepa sales on hand. Consequently, we estimate that this decrease in wholesaler inventory levels adversely impacted net product revenue by approximately $2.8 million to $3.1 million for the first quarter of

2017. During the first quarter of 2016, wholesaler inventory levels adversely impacted net product revenue by approximately $1.2 million to $1.5 million. We believe that changes in channel inventory at these independent wholesalers and

retail pharmacies are common and impacted by numerous factors, including holiday timing and recent order trends. We also deduce, based on information available to us, that channel inventory levels at the end of the first quarters of 2017 and 2016

are within ordinary ranges, and that such levels will continue to vary from quarter to quarter.

Cardiovascular Outcomes Study

The REDUCE-IT cardiovascular outcomes trial continues to progress on

schedule. Amarin anticipates the onset of the final primary cardiovascular event to occur near the end of 2017, with report of top-line results and publications 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 to complete in Q3 2017. We currently estimate that we will report results

of REDUCE-IT in mid-2018, assuming the study goes to completion. These estimates reflect our assumptions of the necessary time needed 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.

Preparations are underway for a second pre-specified interim efficacy and safety analysis of REDUCE-IT by the independent DMC, since we believe that approximately 80% of the primary cardiovascular events occurred in the mid-March timeframe. The ensuing analysis should

be completed 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. We surmise

this because the efficacy requirements detailed to the DMC for early study stoppage after the 80% interim assessment are high. Unlike the data analysis at the end of the study, the interim analysis and review by the DMC also includes robustness

thresholds for certain secondary endpoints. There are potential statistical advantages for the study to run to its full term.

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.

International Development of Vascepa

international initiatives are progressing positively. Our partner for China, Eddingpharm, submitted the clinical trial application (CTA) to the Chinese regulatory authorities in 2016. This CTA was recently approved, enables Eddingpharm to progress

into the clinical testing phase, and potentially positions Vascepa to be the first prescription grade EPA product to receive drug approval in China. We believe the commercial opportunity in China is large based on the prevalence of

hypertriglyceridemia, which is estimated to affect 11.9% of the adult Chinese population. Our partner in China is responsible for the conduct and cost of the clinical studies in China. Amarin will provide the clinical trial material for this study.

Net product revenue for the

three months ended March 31, 2017 and 2016 was $34.3 million and $25.3 million, respectively. This increase in net product revenue was primarily attributable to increases both in new and recurring prescriptions of Vascepa driven by

increased sales productivity and supported by expanded managed care coverage.

In addition, Amarin recognized licensing revenue of $0.3 million and

$0.2 million in the three months ended March 31, 2017 and 2016, respectively, related to agreements for the commercialization of Vascepa outside the United States. Based upon current estimates, Amarin anticipates approximately

$1.2 million in licensing revenue to be recognized in aggregate during 2017 from existing agreements.

Cost of goods sold for the three months ended March 31, 2017 and 2016 was $8.2 million and

$6.9 million, respectively. Gross margin on product sales improved to 76% in the quarter ended March 31, 2017 compared to 73% in the quarter ended March 31, 2016. The improvement in gross margin on product sales was primarily driven

by lower active pharmaceutical ingredient cost.

Selling, general and administrative (SG&A) expenses in the three months ended March 31, 2017 and

2016 were $34.2 million and $28.0 million, respectively. The increase in SG&A expenses primarily reflects a $1.7 million increase in co-promotion fees accrued under our contract with Kowa

Pharmaceuticals America, Inc., increased promotional activities, and increased legal costs. The co-promotion fee is calculated based on gross margin on Vascepa product sales. The increase in co-promotion fees primarily reflects an increase during Q1 2017 compared to Q1 2016 in gross margin on product sales.

Research and development expenses in the three months ended March 31, 2017 and 2016 were $10.8 million and $13.7 million, respectively. This

decrease in expense was primarily driven by the timing of REDUCE-IT expenses.

Under GAAP, Amarin reported a net

loss of $20.9 million in the first quarter of 2017, or basic and diluted loss per share of $0.08. This net loss included $3.4 million in non-cash stock-based compensation expense. Amarin reported a

net loss of $29.8 million in the first quarter of 2016, or basic and diluted loss per share of $0.16. This net loss included $3.6 million in non-cash stock-based compensation expense, a

$1.3 million non-cash loss on the change in fair value of derivatives.

Amarin reported cash and cash

equivalents of $96.1 million at March 31, 2017. Excluding cash flow related to research and development and financing, net cash outflows in the quarter ended March 31, 2017 were approximately $1.4 million. Cash outflows relating

to research and development in Q1 2017 were approximately $10.4 million. Cash flow from financing-type activities included approximately $13.7 million in net cash proceeds from the previously announced January 2017 redemption of debt and

simultaneous issuance of $30.0 million face value of new debt long-term. Cash paid for interest and royalties in Q1 2017 was approximately $4.1 million in aggregate.

As of March 31, 2017, the company had $29.5 million in net accounts receivable ($34.5 million in

gross accounts receivable before allowances and reserves) and $23.9 million in inventory.

As of March 31, 2017, Amarin had approximately

270.7 million American Depository Shares (ADSs) and ordinary shares outstanding, 32.8 million common share equivalents of Series A Convertible Preferred Shares outstanding and approximately 23.5 million equivalent shares underlying

stock options at a weighted-average exercise price of $3.25, as well as 9.8 million equivalent shares underlying restricted or deferred stock units.

Conference call and webcast information

host a conference call at 8:00 a.m. ET today, May 3, 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. The call can also

be heard 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 a replay of the call, dial

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

replay of the call will also be available through the company s website shortly after the call. For both dial-in numbers please use conference ID 10316.

Amarin 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 www.amarincorp.com.

About VASCEPA (icosapent ethyl) capsules

VASCEPA (icosapent ethyl) capsules are a single-molecule prescription product consisting 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 expectations for continued event rates, interim data review, results and related timing and announcements with respect to Amarin s REDUCE-IT cardiovascular outcomes

study; expectations related to the interim and final outcomes of the REDUCE-IT study and the anticipated successful completion of the REDUCE-IT study; and statements

regarding the potential 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, Amarin s ability to effectively develop and commercialize Vascepa will depend in part on its ability to continue to effectively finance its business, efforts of third parties, its ability to create market demand for Vascepa

through education, marketing and sales activities, to achieve increased market acceptance of Vascepa, to receive adequate levels of reimbursement from third-party payers, to develop and maintain a consistent source of commercial supply at a