A federal judge today rejected a bid by generic drug maker Apotex to invalidate the patent of the blockbuster blood thinning drug Plavix, co-marketed by Sanofi-Aventis and Bristol-Myers Squibb.

“This court now finds that Apotex has failed to prove by clear and convincing evidence that the patent is invalid or unenforceable and Sanofi is entitled to a permanent injunction prohibiting Apotex from further infringement,” said US District Judge Sidney Stein, according to a published report.

Stein said he will determine damages in the case at a later date.
 
Last August, Stein stopped Apotex from selling its generic version of Plavix until he could hear the patent case. Apotex began selling its Plavix generic version last August after antitrust regulators rejected a proposed settlement in the case.

Sanofi-Aventis’ patent on Plavix expires in November 2011.

Plavix was the No. 2 selling drug behind Pfizer’s Lipitor in 2005, with global sales of $5.9 billion.