GlaxoSmithKline (NYSE: GSK) and Pronova BioPharma Norge AS won a ruling upholding the validity of patents for the Lovaza heart medicine and delaying the introduction of generic rivals.

U.S. District Judge Sue Robinson in Wilmington, Delaware, concluded Tuesday that Teva Pharmaceuticals USA and Par Pharmaceutical Cos. violated Pronova’s patents on Lovaza, which uses Omega 3 fish oils to help treat heart disease, in their bids to sell cheaper generic versions of the pill.

“The court finds that Pronova has met its burden to provide infringement” and “defendants have not proven” the patents were invalid and unenforceable, Robinson said in a 55-page ruling.

Glaxo, which operates its U.S. headquarters in Research Triangle Park, N.C., markets Lovaza in the U.S. and reported about $913 million in sales of the drug last year.

Par, based in Woodcliff Lake, New Jersey, fell 7.8 percent to $37.70 in New York Stock Exchange composite trading. Teva’s American depositary receipts, equal to one ordinary share, dropped 1.3 percent to $38.10 in Nasdaq Stock Market trading.

Allison Wey, a Par spokeswoman, didn’t immediately return a call for comment on Robinson’s decision.

Denise Bradley, a spokeswoman for Petach Tikva, Israel-based Teva, the world’s largest generic drugmaker, declined to comment.

‘Fully Upheld’

“We are very pleased that all of our challenged patents have been fully upheld,” Morten Jurs, Pronova’s chief executive officer, said in a statement. “We have been confident in our intellectual property rights and have spent considerable resources defending our patents in the U.S.”

Under Robinson’s ruling, Teva and Par must wait until Pronova’s Lovaza patents expire to offer a generic version of the heart treatment. The last patent runs until 2017,

Pronova settled a Lovaza patent dispute with Apotex Inc. last year by allowing Apotex to sell a generic version of the drug in the U.S. in 2015 or earlier, “depending on certain circumstances.”