Pfizer has won a crucial victory in its bid to block the launch of generic alternatives to its blockbuster cholesterol-lowering drug Lipitor (atorvastatin), after a US judge upheld two patents covering the product.

Pfizer now maintains that Lipitor is protected until June 2011. The ruling was a blow for challenger Ranbaxy Laboratories of India, which had asked the courts to invalidate the patents and so clear the way for the launch of its generic version of the $12 billion dollar a year product, the biggest-selling drug in the world.

Ranbaxy immediately said it would appeal the verdict, after Judge Joseph Farnan said that its copycat version of Lipitor infringes one patent held by Pfizer (No 4,681,893), and at the same time upheld the validity of another (No 5,273,995) which Ranbaxy had claimed was invalid.

Pfizer was granted an injunction on sales of generic Lipitor, which will remain in force throughout the appeals process.

The ruling is bad news for Ranbaxy, which like its peers in the US generics sector is feeling the pinch from rising levels of competition and downward pressure on pricing, with more and more companies entering the marketplace. Meanwhile, consolidation among the top players – notably Teva and Sandoz – is creating big generics houses with the reach and product range to negotiate broad and exclusive product supply deals with healthcare payers.

Ranbaxy is among those companies that adopt a high-risk, high-reward strategy in the generic sector, spending on litigation in the hope of winning first-to-market advantage for its generic products.

The Indian company is also challenging Pfizer’s patent position on Lipitor in other countries around the world. Earlier this year, a UK Court ruled in a case between the two firms backed one Pfizer patent, preventing Ranbaxy launching a generic, but invalidated another. This case has also gone to appeal.