On October 1, 2014, the PTAB denied a petition for inter partes review in Torrent Pharmaceuticals, Limited v. Merck Frosst Canada & Co. (Case IPR2014-00559).  The challenged patent was a pharmaceutical compound patent (U.S. Patent No. 6,448,274).  Torrent asserted that the two claims of the patent—a compound claim directed to a single chemical species and a related pharmaceutical composition claim—were invalid based on grounds of anticipation and obviousness.  The chemical species claimed was the active metabolite of roflumilast (the active ingredient in the COPD drug product DALIRESP®).  In support of its petition, Torrent submitted a declaration by a medicinal chemistry expert.  Merck Frosst did not file a preliminary response.

With respect to Torrent’s anticipation arguments, the PTAB held that the cited reference [Fenton]:

. . . does not show the specific combination as illustrated in the challenged claim 1, but only demonstrates classes of possible substituents at various positions. . . Fenton does teach certain subclasses of substituents as preferred; but the scope and content of these subclasses are not so specific as to be deemed a disclosure of the claimed combination. In particular, Fenton does not present so short and selective a list of these subclasses that a person of ordinary skill would, as Petitioner asserts, “at once envisage” the claimed compound. . . ; see Eli Lilly & Co. v. Zenith Goldline Pharm., Inc., 471 F.3d 1369, 1376 (Fed. Cir. 2006).

With respect to Torrent’s obviousness arguments, the PTAB stated:

Petitioner bases its asserted obviousness ground on the structural similarities between the claimed compound and the prior art compounds. . . Generally, in such cases, to establish obviousness of a claimed compound, a challenger of the claim needs to identify some reason that would have led a skilled artisan to select and then modify a known compound. Takeda Chem. Indus., Ltd. v. Alphapharm Pty.Ltd., 492 F.3d 1350, 1357 (Fed. Cir. 2007). The requisite motivation can come from any number of sources, and need not necessarily be explicit in the art. Eisai Co. Ltd. v. Dr. Reddy’s Labs., Ltd., 533 F.3d 1353, 1359 (Fed. Cir. 2008). . . .  Here, even assuming, as Petitioner contends, one skilled in the art would have chosen, separately, difluoromethyl at R1, cyclopropyl-methyl at R2, 3,5-dihalopyrid-4-yl N-oxide at R3, oxygen at both Z1 and Z2, and CONH- at Z3, Petitioner has not sufficiently explained why one skilled in the art would have selected the claimed substituents at each of the six independent positions all at once.  In other words, Petitioner has not shown some objective teaching in the prior art or some general knowledge in the art that would have led one of ordinary skill to combine the relevant teachings of the references to arrive at the claimed invention. . .

Only a limited number of the petitions for inter partes review filed to date have involved a challenge to a pharmaceutical compound patent.  The Torrent decision provides one further example of how the PTAB is approaching such challenges.  Although Torrent included an expert declaration with the petition and Merck Frosst did not submit a preliminary response in rebuttal, the PTAB showed a willingness to strictly adhere to the requirements of the established case law, including the Takeda v. Alphapharm line of cases, in denying the inter partes review.