Unexpected Results Save Patent Claims From Rejection At The PTAB

• Jurisdiction: United States,Federal
• Law Firm: Finnegan, Henderson, Farabow, Garrett & Dunner, LLP
• Subject Matter: Intellectual Property, Patent
• Author: Mr Umber Aggarwal and Amanda Murphy
• Published date: 18 September 2023

Holding

In a series of inter partes review ("IPR") proceedings between JSR Corporation and Cytiva Bioprocess R&D AB,¹ the Patent Trial and Appeal Board ("PTAB" or "Board"), determined that some challenged claims were unpatentable, but others survived based on a sufficient showing of unexpected results.

Background

JSR Corporation ("JSR") asserted obviousness grounds against U.S. Patent Nos. 10,875,007 (the "'007 patent"),² 10,213,765 (the "'765 patent"),³ and 10,343,142 (the "'142 patent"),⁴ all of which related to polypeptide ligands derived from Staphylococcus Aureus Protein A, known as SpA, with an alanine (A) instead of glycine (G) at position 29 of the sequence in the C domain.

Prior art disclosed that a glycine to alanine substitution at position 29 in the sequence of any one of SpAs five domains (A, B, C, D, and E) could help stabilize SpA by eliminating a potential cleavage site, but the prior art did not teach or suggest any reason to specifically target the C domain. Additionally, the prior art taught that the G29A substitution in the B domain rendered Fab binding negligible.

PTAB Decision

The PTAB held several claims of the '007, '142, and '765 patents unpatentable as obvious, noting that the prior art "expressly suggests mutating the glycine codon for an alanine codon in any one of the SPA IgG binding domains E, D, A, B, or C."⁵ The fact that the prior art did not specifically instruct the modification of the C domain was not enough to overcome the 103 grounds. The PTAB also agreed with JSR that "the cited art teaches using these mutant SPA domains in column chromatography for the isolation of antibodies." Id.

However, the PTAB upheld method claims 11 and 29 of the '007 patent and method claims 4 and 17 of the '142 patent based on unexpected results. The claims focused on using a G29A mutant SpA C domain binding "to the Fab part of an antibody" to isolate target compounds. As such, the Board queried whether person of skill in the art would have had a "reasonable expectation that a mutated SpA ligand binds Fab." Id. at *48. The Board found that the cited prior art was "silent with respect to Fab binding to a mutated SpA domain" and one reference supported that "binding to mutated SpA domains [was] unpredictable." Given this, the Board found that the claims recited subject matter covering unexpected results and, thus, were not obvious.

Notably, the PTAB did not apply this rationale to the dependent apparatus claims in the '765 patent, which were...