Norway's Pronova BioPharma , which supplies the omega-3 heart medicine Lovaza to GlaxoSmithKline, has defeated a U.S. patent challenge from two generics companies.

The victory over Teva Pharmaceuticals and Par Pharmaceutical removes the threat of early generic competition to the fish oil-derived drug.

The win in the U.S. District Court for the District of Delaware follows a settlement with another generic drug manufacturer, Apotex, in March 2011 over its patent challenge to Lovaza.

That deal gave Apotex the right to sell a generic version of Lovaza in the United States from the first quarter of 2015, or earlier depending on certain circumstances.

The two Lovaza patents challenged by Teva and Par - which are owned by Pronova and licensed to GSK - expire in 2013 and 2017. The court ruled both patents to be valid.

Pronova Chief Executive Morten Jurs said he was very pleased by the court's decision and looked forward to building up the Lovaza brand in the United States, which is the largest market for the medicine, representing around half of total revenues.

GSK's rights to the drug are confined to the United States and Puerto Rico, where it generated Lovaza sales of 569 million pounds ($892 million) last year.

Pronova -- a world leader in producing pharmaceuticals from fish oils -- is dependent on revenue from sales of Lovaza. More recently, however, its grip on the market has been in doubt due to concerns over a rival medicine being developed by Amarin .

Amarin's new heart pill AMR101 has produced strong results in clinical tests, giving the Nasdaq-listed Irish company ammunition to take on Lovaza.

Both drugs contain heart-protecting omega-3 fatty acids and are designed to treat patients with high levels of triglycerides, a blood fat that contributes to heart disease alongside cholesterol.