On Sep. 29, 2022 Federal Circuit affirmed PTAB (Board) and found sitagliptin phosphate salt patent valid.
Petitioner (Mylan) on Oct 30, 2019 filed inter partes review (IPR) for claims 1–4, 17, 19, and 21–23 of US 7,326,708 patent. US’708 patent is assigned to Merck & it claims dihydrogenphosphate (DHP) salt of sitagliptin. On May 07, 2021, PTAB issued final written decision and found phosphate salt patent of sitagliptin valid. You can read the PTAB decision summary “here” on this blog.
Mylan appealed. Mylan raised three challenges on appeal. First, Mylan contended that Board erred in determining that a 1:1 stoichiometry of sitagliptin DHP was not anticipated, either expressly or inherently, by Edmondson. Second, Mylan contended that the Board erred in determining that the ’708 patent antedates Edmondson. Third, Mylan contended that the Board erred in determining that it failed to prove that claims 3 and 4 of the ’708 patent would have been obvious over Edmondson, Brittain, and Bastin.
With respect to first point, Federal Circuit agreed with Merck & Board that Edmondson does not expressly disclose
a 1:1 sitagliptin DHP salt. Court said that nothing in Edmondson directs a skilled artisan to sitagliptin from among the 33 listed DP-IV inhibitors. Further, nothing in Edmondson singles out phosphoric acid or any phosphate salt of any DP-IV inhibitor, and the list of “pharmaceutically preferred” salts comes 44 pages earlier in the specification. All these possibilities would result in 957 salts, some of which may not exist.
With respect to second point, Federal Circuit agreed with Merck that the Board’s antedation determination was supported by substantial evidence. Merck showed that it developed a 1:1 sitagliptin DHP salt in December 2001 with experimental confirmation in early 2002. The Board’s finding that Edmondson does not disclose 1:1 sitagliptin DHP was supported by substantial evidence; thus, the Board’s finding that it does not disclose a hydrate of that salt was likewise supported by substantial evidence. Court therefore agreed with the Board that Merck reduced to practice “more . . . than what is shown in [Edmondson] for the claimed subject matter.”
With respect to third point, Federal Circuit agreed with Merck that the Board’s decision of validity was supported by substantial evidence. There was no motivation to combine Edmondson and Bastin / Britain to make sitagliptin DHP, that the cited references did not provide motivation to make (S)-sitagliptin, and that there was no reasonable expectation of success in combining the references. The Board also credited Merck’s expert, Dr. Myerson, who
stated that a skilled artisan would have sought to avoid hydrates. Federal Circuit thus found no error in Board’s determination and affirmed the decision.