Pfizer just received an initial communication from the USPTO regarding Lipitor's basic patent. And the news is not good. Will Pfizer keep its hold on the world's biggest-selling drug?

Pfizer Inc. recently announced that the U.S. Patent & Trademark Office (USPTO) has issued its first communication in the reexamination of the ‘893 basic patent for Lipitor, initially rejecting the patent’s claims. This 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 those issues raised by the examiner. The USPTO's move was in response to a request for a reexamination by a law firm representing Indian generic drug maker Ranbaxy Laboratories.

The patent, which expires in March 2010, remains valid and enforceable during the period of reexamination, which could take as long as a few years. Given that Lipitor sales amount to about $12 billion, this is good news for Pfizer which can then continue to fend off its generic competitors.

According to Pfizer, an initial rejection is not unusual in reexamination proceedings. “We will respond as appropriate to the issues raised by the examiner, and believe we have compelling arguments in our favor,” said Pfizer General Counsel Allen Waxman. “We continue to believe that the basic patent was properly granted and will be upheld on reexamination. This initial action, which was not unexpected, does not change that.”

The Pfizer-Ranbaxy battle over Lipitor is not new and started when Pfizer sued Ranbaxy in response of Ranbaxy’s Abbreviated New Drug Application (ANDA) No. 76-477 filed with the FDA, seeking marketing approval for the generic bioequivalent of Atorvastatin Calcium. Pfizer filed patent infringement lawsuit in the U.S. District Court for the District Court of Delaware alleging infringement of U.S. Patent # 4,681,893 (the ‘893 patent) and U.S. Patent # 5,273,995 (the ‘995 patent) under 35 U.S.C. § 271 (e)(2).

In response, Ranbaxy alleged that it does not infringe either the ‘893 or ‘995 patents; additionally, it challenged the validity of the patent term extension granted for the ‘893 patent and contented that the claim 6 of the ‘995 patent is invalid for double patenting, obviousness and anticipation.

In 2006, the US Court of Appeals for the Federal Circuit ruled that claim 6 of the '995 patent invalid, although it upheld a lower court's findings that Ranbaxy had infringed the '893 patent and that the '893 patent term extension was not  invalid.

It is in fact the very same '893 patent, last granted in 1987 and assigned then to Pfizer unit Warner Lambert Co., which is at issue today. In August 2007, Pfizer had asked the USPTO to reissue the patent in order to retain its market grip on Lipitor through 2011. The patent office refused. Ranbaxy had opposed the move on the grounds that Pfizer had a weak statutory justification for the reissue – saying that too many of the '893 patent's claims, which cover a method for producing the drug, were already anticipated by prior art.

Not surprisingly, this is just one among the many worldwide battles Pfizer has been fighting to keep generics makers from cashing in on a very profitable drug. The question is: Is this latest development just a temporary setback for Pfizer and a win for generic drugs?

Pfizer is the world's largest research-based biomedical and pharmaceutical company with corporate headquarters in New York and major research and development locations in the United States and England. Ranbaxy Laboratories Limited, headquartered in India, is an integrated, research based, international pharmaceutical company, producing a wide range of quality, affordable generic medicines.

Lipitor is the trade name for Atorvastatin, a member of the drug class known as statins, used for lowering cholesterol. Atorvastatin inhibits the rate-determining enzyme located in hepatic tissue that produces mevalonate, a small molecule used in the synthesis of cholesterol and other mevalonate derivatives. This lowers the amount of cholesterol produced which in turn lowers the total amount of LDL cholesterol.

Lipitor is the largest selling drug in the world with 2006 sales of US$12.9 billion. A similar drug, simvastatin, is available as a cheaper generic alternative.

http://en.wikipedia.org/wiki/Lipitor