May 28 (Reuters) - A U.S. district court has ruled that Amarin Corp's fish oil pill, Vascepa, is eligible for five years of marketing exclusivity, setting aside a U.S. Food and Drug administration decision.

Amarin's shares rose as much as 44 percent to $2.80 on the Nasdaq. The stock was trading up 19 percent at $2.33 on Thursday afternoon.

Vascepa was approved in 2012 to reduce high levels of blood fat called triglycerides in patients not using cholesterol-lowering statins.

The case is Amarin v. U.S. FDA and HHS, U.S. District Court for the District of Columbia, No. 14-cv-00324. (http://1.usa.gov/1QdfHeC) (Reporting by Natalie Grover and Ankur Banerjee in Bengaluru; Editing by Don Sebastian)