By Donald Zuhn --
Yesterday, Gilead Sciences, Inc. announced that the U.S. Patent and Trademark Office had issued a Notice of Intent to Issue an Ex Parte Reexamination Certificate for U.S. Patent No. 5,922,695. The '695 patent became the second of Gilead's four Viread® (tenofovir disoproxil fumarate) patents to survive reexamination. Last month, Gilead announced that U.S. Patent No. 6,043,230 had also survived reexamination. Still in reexamination proceedings are Gilead's U.S. Patent Nos. 5,977,089 and 5,935,946.
The four reexamination proceedings were initiated in response to an ex parte reexamination request filed by the Public Patent Foundation (PUBPAT) on March 23, 2007. While PUBPAT has devoted a page on its website to the Viread® patents, it has not yet posted a comment concerning either of the Patent Office's determinations regarding the '695 and '230 patents.
In the Notice of Intent issued with respect to the '695 patent, the Patent Office indicated that the patentee had overcome a 102(a) rejection of claim 1 over one reference by submitting a Rule 131 declaration showing that the inventors had prepared bis (isopropyloxy carbonyloxymethyl) PMPA in the United States prior to January 1997. The Office also explained that a 103(a) rejection in view of three references and the patentee's own admission had been overcome by the patentee's arguments made during reexamination proceedings. The Office further indicated that the patentee had established that bis carbonate prodrugs of PMPA are unexpectedly stable and useful, these prodrugs have satisfied a long felt need in the anti-HIV drug art, and that the invention is commercially successful.
The '695 patent is directed to a compound comprising an antiviral phosphonomethoxy nucleotide analog and the '230 patent is directed to a method comprising contacting a cell with such a compound. In the company's press relaease, Gilead Senior Vice President and General Counsel Gregg Alton noted that the '695 patent was "the most integral to Viread's novel exclusivity," and stated that the company was "pleased with the PTO's swift analyses and actions, which have confirmed the strength of [Gilead's] patent position."
On Gilead's Viread® homepage, the drug is described as being a member of the nucleoside reverse transcriptase inhibitor (NRTI or "nuke") family of molecules. Viread®, which helps to block reverse transcriptase by interfering with the replication process (as shown in an animation on the Viread® homepage), can be used in combination with other HIV medications for the treatment of HIV-1 infection.