Pfizer: Lipitor Reissue Patent Application Rejected

As The Wall Street Journal reported last week, the U.S. Patent and Trademark Office has issued an initial rejection of Pfizer's application for a reissue patent of U.S. Patent No. 5,273,995--one of two Pfizer (PFE) patents covering Lipitor.

In a decision last August, the Court of Appeals for the Federal Circuit upheld one Pfizer patent on Lipitor (U.S. Patent No. 4,681,893) and invalidated another (the '995 patent).

Specifically, the court invalidated claim 6 of the '995 patent, covering the hemicalcium salt of atorvastatin acid (the active ingredient in Lipitor), because it failed to specify a further limitation to the claim from which it depended.  Pfizer sells about $12 billion worth of Lipitor annually.

The '995 patent (if valid) was set to expire more than a year later than the '893 patent will expire, so naturally Pfizer filed a reissue patent application to try to correct the '995 patent.

In a preliminary amendment filed as part of its reissue application in January, Pfizer amended claim 6 of the '995 patent to be an independent claim, and indicated that "this was one of the options . . . approved by the Federal Circuit in its decision." Ranbaxy--the first ANDA filer for generic Lipitor and the defendant in the patent litigation decided by the Federal Circuit--filed a protest against Pfizer's reissue application in May.]

Among Ranbaxy's arguments was that the defect in claim 6 is not correctable through a reissue patent. The Patent Office mailed a first Office Action on Pfizer's reissue application last Thursday.  While the Patent Office stated that the defect in claim 6 is in fact correctable through a reissue application, the Office rejected all 14 claims of Pfizer's reissue application on grounds of anticipation, obviousness, or obviousness-type double patenting.

In particular, the Office rejected claim 6 for obviousness-type double patenting in view of U.S. Patent Nos. 6,605,729 and 5,969,156.

The proceedings over Pfizer's reissue patent application are far from over. Pfizer will certainly file a response to last week's Office Action, after which the Patent Office might issue a final Office Action. If Pfizer is unsatisfied at that point, it might request continued examination or file an appeal to the Patent Office Board of Appeals. If rebuffed there, Pfizer could appeal to the Federal Circuit.

Given how much money is at stake, Pfizer is likely to pursue all its options before giving up on the reissue application.

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Earlier OBB posts on Lipitor litigation: 29 Jan 07; 23 Oct 06; 31 Aug 06