GlaxoSmithKline and partner Pronova BioPharma are celebrating after the latter beat off a patent challenge to their fish oil heart drug Lovaza from Teva and Par Pharmaceuticals.

After a three-year case, a US court in  Delaware has found that Pronova's claims on two patents are valid, enforceable and would be infringed by Teva and Par, who had made the challenge over Lovaza (omega-3-acid ethyl esters). The patents in the drug are owned by the Norwegian company and licensed to GSK in the USA and Puerto Rico,

The two patents challenged by Teva and Par expire in 2013 and 2017. In March last year, Pronova entered into an agreement with Canada's Apotex to settle litigation and grant the latter a license to enter the US market with a generic version of Lovaza in the first quarter of 2015, or earlier depending on certain circumstances.

Pronova chief executive Morten Jurs said that "we have been confident in our intellectual property rights and have spent considerable resources on defending our patents in the USA". He added that "we look forward to continue building the Lovaza brand in our largest market" - the latter represents about half of total revenues for the product.

The drug is a big earner and GSK booked first-quarter sales of £151 million, up 17%.