Nov. 2 (Bloomberg) -- Bristol-Myers Squibb Co. and Sanofi- Aventis SA won a U.S. Supreme Court fight over their $9.5 billion-a-year Plavix blood thinner as the justices refused to question a patent that bars generic versions until November 2011.

The justices today turned away an appeal by Canadian drugmaker Apotex Inc., which sought to invalidate the patent that protects Plavix, the world’s No. 2 selling drug, in the U.S. An earlier Sanofi patent on the drug expired in 2003, and Apotex said the disputed second patent covered a variation that wasn’t innovative enough to warrant legal protection.

“The second patent’s only function has been to prolong Sanofi’s monopoly by eight years,” Apotex argued in its unsuccessful appeal.

The rebuff boosts Bristol-Myers and Sanofi as they seek reimbursement from Apotex for its decision to enter the market in 2006. New York-based Bristol-Myers, which sells Plavix in the U.S. under an agreement with Paris-based Sanofi, has said it lost as much as $1.75 billion in sales after Apotex flooded the market during a three-week period.

The companies “have always believed” that the patent is “valid and enforceable and will continue to defend their intellectual property rights in Plavix,” said Laura Hortas, a spokeswoman for Bristol-Myers.

Bristol-Myers fell 3 cents to $21.77 in New York Stock Exchange composite trading. Sanofi American depositary receipts, each representing one-half of an ordinary share, fell 42 cents to $36.50.

2008 Sales

Plavix generated combined 2008 sales of about $9.5 billion for Bristol-Myers and Sanofi, which sells the drug outside the U.S. Pfizer Inc.’s Lipitor is the world’s biggest-selling drug.

Bristol-Myers and Sanofi units argued in court papers that the disputed patent covered “a new, breakthrough drug compound that took years and millions of dollars to develop.” They urged the Supreme Court not to review a federal appeals court decision upholding the patent.

In a separate proceeding, the U.S. Patent and Trademark Office is reconsidering whether the patent should have been issued.

The case is Apotex v. Sanofi-Synthelabo, 09-117.

To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.net.

Last Updated: November 2, 2009 16:13 EST