Pfizer in danger of losing Lipitor patent. Source: Cutting Edge Pharma

The U.S. Patent & Trademark Office has rejected the reexamination of Pfizer’s ‘893 basic patent’s claims for Lipitor. The current patent is set to expire in 2010.

The initial action, which is how the Office raises its issues with the patentee, will now be followed by the company’s response, in which Pfizer will address the issues raised by the examiner.

Allen Waxman, Pfizer’s general counsel, said, “We will respond as appropriate to the issues raised by the examiner, and believe we have compelling arguments in our favor. We continue to believe that the basic patent was properly granted and will be upheld on reexamination.”

Lipitor is one of the world’s top-selling drugs, with sales of approximately $13 billion in 2006.

The patent remains valid and enforceable throughout the re-examination proceeding, which could take as long as a few years, the New York City-based Pfizer said. The pharmaceutical giant has requested that the patent office issue a second Lipitor patent to extend its rights to the drug until June 2011.