Oslo, March 23 - Pronova BioPharma , which makes diet supplements from fish oil, said U.S. drug group Par Pharmaceutical aimed to launch a generic version of Pronova's prescription drug Lovaza, sending its shares down.
"Pronova has full confidence in its intellectual property portfolio protecting Lovaza and will vigorously defend and enforce its patents," the Norwegian company said in a statement.
Shares in Pronova had fallen 3.6 percent to 16 crowns by 1325 GMT, against a 1.7 percent rise in the Oslo bourse's benchmark index.
Pronova's Lovaza, branded in Europe and Asia as Omacor, is a dietary supplement based on fish oil, a rich source of omega-3 fatty acids.
Pronova said it and its partner GlaxoSmithKline had received notice in a March 17 letter advising it that Par Pharmaceutical had submitted an application to the U.S. food and drug administration (FDA) for approval to market a generic version of Lovaza.
GlaxoSmithKline snapped up U.S. rights to Pronova's product in 2007 by acquiring Reliant Pharmaceuticals for $1.65 billion.
Omega-3 fatty acids have in the past been linked to a range of health benefits, including reducing the risk of heart attack, stroke, Alzheimer's disease and depression.
Pronova spokeswoman Hilde Steineger said end-user sales of Lovaza were close to $1 billion in December last year, making it close to a "blockbuster drug" in the United States.
"We will ask for more information to see if they are infringing on our patent," Steineger said.
Pronova BioPharma says on its website that Lovaza/Omacor is "the only EU- and FDA-approved omega-3 derived prescription pharmaceutical product".