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.


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 similarly directed to Fab bindings but only recited that a "ligand [is] capable of binding to the Fab part of the antibody" (emphasis added). The PTAB reasoned that "[t]he 'capable of binding' language of [the apparatus claims of the '765 patent] does not add any structural limitations [but] merely recites the function of the composition when used for example in an assay." Id. at *46. The PTAB concluded that "the Fab binding ability," as recited in the apparatus claims, was an "inherent feature" and did not add any patentable scope. Id. at *48.


Unexpected results may undermine an obviousness challenge. Discovering that a species within a genus exhibits a characteristic that other species in the same genus do not may support a showing of unexpected results.

However, the language of a claim is important when analyzing unexpected results. For example, one may show that a method claim recites a step that describes an unexpected result. But a counterpart apparatus that merely recites the capability to perform that step may not achieve the same result, as seen in this case.

A word about inherency and obviousness. Inherency arguments are subtle obstacles to the patent owner defending a claim. Although in principle, that which is not known cannot be obvious, (In re Shetty, 566 F.2d 81, 86 (C.C.P.A. 1977)), there is case law approving the application of inherency theories in obviousness. See, e.g., Persion Pharms. LLC v. Alvogen Malta Operations Ltd., 945 F.3d 1184, 1190 (Fed. Cir. 2019) ("Inherency may supply a missing claim limitation in an obviousness analysis. An inherent characteristic of a formulation [i.e. composition] can be part of the prior art in an obviousness analysis even if the inherent characteristic was unrecognized or unappreciated by a skilled artisan."). But remember, "[a] party must . . . meet a high standard in order to rely on inherency to establish the existence of a claim limitation in the prior art in an obviousness analysis." Millennium Pharms., Inc. v. Sandoz, Inc., 862 F.3d 1356, 1367 (Fed. Cir. 2017); see also, Honeywell Int'l Inc. v. Mexichem Amanco Holding S.A. de C.V., 865 F.3d 1348 (Fed. Cir. 2017).


1. IPR2022-00042, IPR2022-00045, Paper 40 (P.T.A.B. May 18, 2023); IPR2022-00041, IPR2022-00044, Paper 40 (P.T.A.B. May 18, 2023); and IPR2022-00036, IPR2022-00043, Paper 41 (P.T.A.B. April 19, 2023).

2. IPR2022-00042 and IPR2022-00045.

3. IPR2022-00036 and IPR2022-00043.

4. IPR2022-00041 and IPR2022-00044.

5. IPR2022-00042 and IPR2022-00045 at *36.

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