There was bad news for Amarin as FDA advisors called for a delay to expanding use of its fish oil heart drug until more efficacy data becomes available, and shareholders triggered a financial fraud investigation following this week's stock plunge.

The US Food and Drug Administration's Endocrinologic and Metabolic Drugs Advisory Committee panel has voted nine-two against green-lighting the use of Vascepa (icosapent ethyl) to treat high levels of triglycerides in patients with heart disease who are taking statins.

The drug was approved in July last year for the treatment of patients with severe hypertriglyceridemia; expanding the patient population to that of the proposed new indication would significantly boost its sales.

But review documents show that investigators are not convinced that Vascepa's triglyceride-lowering capabilities actually induce a significant clinical benefit.

"I'm optimistic about the data presented today by Amarin. I am wary, however, of approving a drug that has a potential market of tens of millions of people without hard efficacy data," Brendan Everett of Harvard Medical School, who voted against the drug, reportedly said (as reported by the Associated Press).

Share plunge

Earlier this week, Amarin shares fell more than 20% after pre-meeting briefing documents were released by the FDA, which included questions about the mineral oil placebo, potentially negatively impacting the control group data and consequentially overstating Vascepa’s effectiveness.

While the post-meeting documents show that the panel agrees that the drug is indeed able to lower triglycerides, there seems to be uncertainty over the magnitude of this benefit.

This has prompted shareholders to launch as investigation into whether Amarin's Board of Directors have violated any federal securities laws.

A final decision by the FDA is expected by December 20.