Pfizer's Lipitor '893 Patent Survives Reexamination

    By Donald Zuhn --

On Wednesday, Pfizer announced that it had received a Notice of Intent to Issue an Ex Parte Reexamination Certificate for U.S. Patent No. 4,681,893 from the U.S. Patent and Trademark Office.  The '893 patent, which expires in March 2010, is directed in part to atorvastatin, the active ingredient in Pfizer's cholesterol-reducing drug Lipitor®.  Pfizer noted that "it is pleased with the decision, which affirms the company’s position that the patent was properly granted."

The reexamination request (Reexamination No. 90/008,727) was filed by Ranbaxy Laboratories Ltd. in July 2007.  Ranbaxy had sought reexamination of the '893 patent after waging an unsuccessful battle to invalidate the patent in federal court; in August 2006, the Federal Circuit affirmed a District Court finding that Ranbaxy had infringed the '893 patent (while also reversing the District Court and finding another Pfizer atorvastatin patent, U.S. Patent No 5,273,995, invalid).

In the Notice of Intent's Statement of Reasons for Patentability and/or Confirmation, the Examiner indicated that Pfizer had overcome obviousness rejections based on European Publication No. EP 0 179 559 and U.S. Patent No. 4,647,576.  With respect to the '559 publication, Pfizer submitted a Declaration establishing that the '559 publication has the same inventor as the '893 patent, is therefore not by "another," and as a result is no longer available as prior art under 35 U.S.C. § 102(a).  With respect to the '576 patent, the Examiner determined that neither the '576 patent, nor any of the other prior art cited by Ranbaxy, would have led a chemist to substitute the carboalkoxy of the closest prior art compound (described in the '576 patent) with the carboxamide of atorvastatin of the '893 patent.  Quoting Takeda Chem. Indus., Ltd. v. Alphapharm Pty., Ltd., the Examiner noted that "in cases involving new chemical compounds, it remains necessary to identify some reason that would have led a chemist to modify a known compound in a particular manner to establish prima facie obviousness of a new claimed compound."  With respect to the reexamination of the '893 patent, the Examiner determined that no such reason existed.

A second request for ex parte reexamination (Reexamination No. 90/009,048) filed by Ranbaxy on February 22, 2008 was denied by the Patent Office on April 9, 2008.

Comments

[Atorvastatin Ace]

Don, as I recall the Fed Circuit invalidated claim 6, the asserted claim, of the '995 patent for improper dependency, but didn't invalidate the whole patent. I'm glad to see, however, that the '893 patent survived reexam - this was the first patent covering atorvastatin, and say what you might about follow-on patents (like the '995 directed to the enantiomeric calcium salt, or the later patents on crystalline forms of atorvastatin), Pfizer certainly deserved this one. But I guess with $10B+ per year at stake, Ranbaxy thought it was worthwhile to tilt at this windmill.