Predictably, A Funny Thing Happened On The Way To The PTAB FWD - Part 1: Merck Overcomes Inherent Anticipation Challenge At The PTAB

• Published date: 23 September 2021
• Subject Matter: Intellectual Property, Patent
• Law Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP
• Author: Ms Adriana Burgy, Stacy Lewis and Thomas L. Irving

Overcoming anticipation assertions is a hurdle many patent owners face, both at examination, and later when challenged at the PTAB. Merck Sharp & Dohme Corp. ("Merck"), however, recently overcame a challenge of inherent anticipation by Mylan Pharmaceuticals ("Mylan") by relying on the complexities of chemical salt formation.

The patent at issue, U.S. Patent No. 7,326,708 ("the '708 patent") claims a "1:1 sitagliptin DHP," a salt comprised of "one phosphate anion" in conjunction with "one sitagliptin amine cation." DHP is a dipeptidyl peptidase-IV inhibitor used to lower blood sugar and is the primary ingredient in Merck's Januvia drug for Type 2 diabetes.

Filing IPR2020-00040 in October of 2019, Mylan sought to render claims of the '708 patent unpatentable on grounds of anticipation, inherent anticipation, and obviousness. While the PTAB methodically walked through each of Mylan's arguments, this article, Part 1, focuses on Mylan's unsuccessful inherency arguments. Part 2 will focus on Mylan's equally unsuccessful obviousness arguments.

In asserting inherent anticipation, Mylan primarily relied on WO 03/004498 ("the WO '498 publication") as anticipatory prior art. WO '498 is also owned by Merck. WO '498 claims peptidase-IV enzymes, or DP-IV inhibitors, used to treat high blood sugar. Mylan Pharms. v. Merck Sharp & Dohme Corp., IPR No. 2020-00040, at 16 (P.T.A.B. May 7, 2021).

Mylan asserted that the WO '498 publication taught a 1:1 phosphoric sitagliptin salt by disclosing two "closed lists." Id. at 20. Mylan argued that one list included sitagliptin as one of 33 potential compounds, and another list identified phosphoric acid as one of eight preferred acids. Mylan claimed that a person of ordinary skill would see these two closed lists, know to combine the two compounds, and, similar to the chewing gum combination in Wrigley, create the 1:1 sitagliptin DHP claimed in the '708 patent.

In response, Merck distinguished Mylan's "combination lists" argument. Merck urged that a list-based analysis under Wrigley was incorrect regarding the '708 patent. In Wrigley, the Federal Circuit found anticipation because two chewing gum components, the flavoring agent and the cooling agent, were both disclosed in the prior art in closed lists as "preferred agents," and therefore a person of ordinary skill would have thought to combine them to create the claimed product. Here, to create the 1:1 sitagliptin DHP, a skilled artisan would not only have to combine the...