WASHINGTON (Legal Newsline) - Bristol-Myers Squibb Co. and Sanofi-Aventis SA won a major legal fight Monday over their blood thinner Plavix when the U.S. Supreme Court rejected an appeal challenging the drug's patent.

Apotex Inc. was sued over patent infringement violations after the generic drug maker applied to market a version of Plavix before its original patent expired in 2003.

The Canadian generic drug maker Apotex argued that a secondary patent that France-based Sanofi had on Plavix's two main molecules should not have been granted. That patent does not expire until 2011.

"The second patent's only function has been to prolong Sanofi's monopoly by eight years," Apotex argued in court papers.

Plavix was developed by Sanofi-Aventis SA and co-marketed by Bristol-Myers Squibb Co., based in New York. The drug works to prevent blood clots in coronary artery disease, peripheral vascular disease and cerebrovascular disease.

A U.S. District Court judge and the U.S. Court of Appeals for the Federal Circuit both upheld the patent's validity.

Separately, Apotex has filed a request that the U.S. Patent and Trademark Office reexamine the secondary patent on the anti-blood-clotting drug.

The U.S. Supreme Court case is Apotex v. Sanofi-Synthelabo, 09-117.

From Legal Newsline: Reach staff reporter Chris Rizo at chrisrizo@legalnewsline.com.