Amarin Corp. plc has brought its fight over the heart drug Vascepa to federal court, suing the U.S. Food and Drug Administration over its decision to grant only three years of marketing exclusivity for its fish-oil pill rather than the usual five-year approval.

"FDA's decision is contrary to law," Amarin said in a court filing dated Thursday that named the FDA, FDA Commissioner Margaret A. Hamburg and Kathleen Sebelius, secretary of the Department of Health and Human Services, as defendants. "FDA's action is also arbitrary and capricious."

Amarin stock fell more than 2 percent Friday following release of the biotech company's fourth-quarter financial results, which were slightly below expectations. Word of Amarin's lawsuit first was reported by Business Week, but wasn't mentioned during a conference call with Amarin executives Thursday afternoon

The Irish drug company, with research headquarters in Groton, finished the day at $1.74 a share, down 4 cents on the Nasdaq exchange, after releasing its quarterly and year-end reports late Thursday. The decline came as Amarin's revenue for the quarter hit $10.1 million, off more than $1 million from Wall Street projections.

"We are confident in our ability to achieve continued revenue growth from Vascepa based upon its current indication," John Thero, Amarin chief executive, said during the call, according to a transcript available at www.SeekingAlpha.com.

In its lawsuit, however, Amarin complained that the FDA had changed its policy on marketing exclusivity and then applied the new way of doing business "retroactively to Vascepa."

"Amarin should not be penalized because - after Amarin developed and secured approval for Vascepa - FDA has decided to adopt a new policy that conflicts with its past practice," the company's lawsuit contended.

The FDA does not comment on pending litigation.

Amarin contends that the FDA had never before approved a product that identified Vascepa's key ingredient, icosapent ethyl, as an active ingredient. Lovaza, another fish oil pill that, like Vascepa, treats high triglycerides that can affect heart function, has an "undifferentiated" mixture that includes icosapent ethyl, but that specific ingredient was never identified as the reason for Lovaza's effect, Amarin said.

In its year-end report, Amarin said it had realized $26.4 million in Vascepa sales last year, the first year the product made money. The company said more than 16,000 doctors now are prescribing Vascepa, which has been shown to lower blood fat that can lead to heart problems.

"As we embark on our second year as a commercial organization we stand by our commitment to work toward label expansion for Vascepa to improve treatment options for patients," Thero said in a statement.

Amarin reported having a cash cushion of $191.5 million at year's end, which Thero said should allow the company time, with increasing sales, to reach a cash-flow positive position without having to seek additional capital to fund continuing studies.

l.howard@theday.com