What happened

Shares of Amarin Corporation plc (NASDAQ:AMRN), a biopharmaceutical company that specializes in cardiovascular health, rose 34.3% in June according to data from S&P Global Market Intelligence. Positive clinical trial data concerning its lead drug, Vascepa, gave the market a reason to cheer.

So what 

Amarin's Vascepa earned FDA approval in 2012 for the treatment of patients with circulating triglyceride levels above or equal to 500 mg/dl, a group that includes around 2% of the U.S. population. After a lengthy legal battle, the company also markets the fish oil derivative off-label to about 16% of the U.S. population with triglyceride levels in the 200 mg/dl to 499 mg/dl range despite treatment with statins.

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Last month, the stock started jumping after Amarin presented a post hoc analysis of the Anchor trial. The company showed that Vascepa significantly lowered triglyceride levels among statin-treated women with type-2 diabetes. The data could help the company market the drug off-label to this group -- and significantly boost sales in the process.

Now what

An estimated one in three Americans is at risk of developing diabetes, and cardiovascular disease is one of the most common co-morbidities. Although high triglyceride levels are associated with increased risk of heart attack and stroke, there are lingering doubts about whether or not lowering them with Vascepa will actually reduce that risk.

Those doubts could lift or strengthen by the end of the year. In 2011, the company began an 8,175-patient trial to see if Vascepa treatment could significantly reduce the long-term risk of heart attack and other cardiovascular events. The company expects it will be able to present data from an interim analysis of the outcome study during the present quarter. The results of that data will dictate whether the stock will continue to soar or plummet.

Cory Renauer has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.