Pfizer’s patent on Norvasc nullified

Pfizer Inc.’s patent on the hypertension drug Norvasc was invalidated by an appeals court Thursday, opening the way for generic competition to the company’s second-biggest seller.

The U.S. Court of Appeals for the Federal Circuit in Washington held invalid the patent on the drug’s key ingredient, amlodipine besylate, overturning a January 2006 ruling by District Judge James M. Rosenbaum in Chicago.

Because the drug is an “obvious” variation of earlier inventions, the patent is invalid, Chief Judge Paul Michel wrote in a 41-page opinion. Pfizer said it might appeal the decision.

Norvasc is Pfizer’s second-biggest seller behind the cholesterol treatment Lipitor. The blood-pressure medicine had $4.87 billion in sales last year, or more than $13 million a day for New York-based Pfizer, the world’s biggest drug maker. The drug patent expires in September, and Mylan Laboratories Inc. has final approval from the Food and Drug Administration to market a generic version.

“It appears now that Mylan should be able to launch its product with exclusivity immediately,” JPMorgan Chase & Co. analysts said in a report. “Assuming six months of sales, we believe Mylan could record more than $300 million of revenue.”

Mylan shares rose $1.01, or 5.2%, to $20.55. The company, based in Canonsburg, Pa., had total sales of $1.26 billion in the fiscal year through March 2006. Pfizer shares fell 6 cents to $25.79.

“Pfizer is reviewing the decision and is considering all its options, including seeking reconsideration,” the company said in a statement Thursday.