Pfizer: US ruling maintains Lipitor patent term

The U.S. Patent & Trademark Office issued a notice Tuesday allowing drug maker Pfizer Inc. to correct a technical defect in one of the patents involving Pfizer’s cholesterol medicine Lipitor, the world’s top-selling drug.

The decision will result in reissuance of the drug’s key patent and maintain that patent’s June 2011 expiration date, crucial to Pfizer because Lipitor brings the company nearly $13 billion in annual sales.

That revenue has made the drug, and New York-based Pfizer, the target of litigation by generic drug makers hoping to roll out cheaper versions earlier and capture part of the market for one of the top classes of drugs.

“We have said all along that we had strong arguments for securing the reissue of the patent, and after a vigorous and thorough examination, the patent office agreed with this conclusion,” Raymond F. Kerins, vice president of worldwide communications at Pfizer, said in a statement.

Tuesday’s patent office decision resulted from litigation that began after India’s largest drug maker, Ranbaxy Laboratories Ltd., in 2002 sought U.S. Food and Drug Administration approval to sell a generic version of Lipitor, which is known chemically as atorvastatin. Ranbaxy challenged both Lipitor’s basic patent and a second one.

The June 2011 expiration date includes a six-month extension of the original expiration date granted because Pfizer did research after the drug was approved to determine its safety and effectiveness in children -- a standard move by drug companies to preserve revenue of their most lucrative drugs. Ranbaxy can begin selling generic Lipitor as of Nov. 30, 2011. As the first company to seek FDA approval to sell a generic, it can do so for six months exclusively.