In following the status of the reexamination request on Pfizer’s Viagra (sildenafil citrate) patent (U.S. Pat. No. 6,469,012), we find that Pfizer has filed a response to the outstanding Nonfinal Office Action.

See the Nonfinal Office Action here.

To recap, Pfizer filed a patent infringement lawsuit against ICOS, Lilly ICOS, and Lilly in the United States District Court contending that the use, offering for sale, selling, manufacture, or importing into the United States of Cialis for the treatment of erectile dysfunction by any of the defendants infringes claim 24 of Pfizer’s U.S. Patent No. 6,469,012.

The USPTO subsequently ordered the reexamination of the Pfizer Patent (Reexam. C.N. 90/007,478) and in the first office action issued by the PTO, the Examiner rejected claim 24 of the Pfizer Patent.

Claim 24 reads:

A method of treating erectile dysfunction in a male human, comprising orally administering to a male human in need of such treatment an effective amount of a selective cGMP PDEv inhibitor, or a pharmaceutically acceptable salt thereof, of a pharmaceutical composition containing either entity.

This broad claim would cover treatment by any cGMP PDEv inhibitor (read: Cialis) and was rejected over the references Korenmann, 41 J. Am Geriatrics Soc. 363 (1993) and Yin et al., 10(6) Yunnan J. Traditional Chinese Medicine 13 (1989).

The Examiner rejected claim 24 on the basis that certain prior art rendered the claimed invention not new, and therefore unpatentable under 35 U.S.C. §102(b), and obvious and unpatentable under the judicially created doctrine of obviousness-type double patenting.

On September 15, 2005, the USPTO issued a second office action that rejected Pfizer’s arguments made in response to the first office action, reaffirmed the initial rejection of claim 24, and entered new grounds for rejecting claim 24. The second office action also maintained the obviousness-type double patenting rejection of the other claims.

Pfizer has now filed a Response arguing that the Examiner employed applied a one-way test of obviousness for claim 24 in finding obviousness-type double patenting over claim 1 of each of U.S. Pat. Nos. 6,534,511, 6,100,270 and 6,656,945, and that there is no double patenting under this test. They have argued that simply because an invention falls within a range disclosed by the prior art does not necessarily make it per se obvious. Both the genus and species may be patentable.

Pfizer also contends that the Patent Office had not met the burden of proof for establishing unpatentability stating that the reports relied upon by the Patent Office, as well as patentee’s own submissions, demonstrate there is no basis to conclude that pentoxifylline is a PDEV selective inhibitor or that it is effective in treating ED as required by claim 24.

Pfizer claims that the evidence the Patent Office relied upon is based on “junk science” that should not be accorded any weight (i.e., reports based on scientifically invalid methodology and lacking statistical significance, sometimes referred to as “junk science,” should not be relied upon. (Daubert v. Merrell Dow Pharm., Inc., 43 F.3d 1311,1322 (9th Cir. 1995)).

Regarding Claim 24 the Second Reexam Office Action states that “Bensky, Hsu, Chang & But and Yin individually teach the use of Yin Yang Huo in oral compositions to treat impotence.” The Patent Office also found that, although these references do not disclose that Yin Yang Huo is a selective cGMP PDEV inhibitor, “the scientific literature … establishes that the main ingredient of Yin Yang Huo-containing compositions, icariin, is a selective cGMP PDEV inhibitor.”

Pfizer now argues that there is no evidence that a PDEV selective inhibitor contained in Yin Yang Huo treats ED and that there is no evidence that icariin is the compound that treats ED – even assuming that anything in Yin Yang Huo treats ED.

We’ll keep you posted on further actions on this matter.

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