Antibody Claim Strategies After the Amgen v. Sanofi DecisionsMarch 11, 2021

Monoclonal antibodies (“mAb”) which specifically bind therapeutic targets dominate the biopharmaceutical market with global sales revenues estimated at nearly US$163 billion in 2019. Prior to the 2017, mAb were often protected in the US by broad claims which described the therapeutic target (i.e., the “antigen”) that the mAb could bind since such mAb could be obtained by routine experimentation. This practice effectively ended when the United States Court of Appeals for the Federal Circuit (“CAFC”) held that such functionally limited claims did not meet the “written description” requirement of 35 USC 112 (Amgen v. Sanofi (CAFC, 872 F.3d 1367 (2017); Cert denied; 139 S.Ct. 787 (2019)), noting that the previously applied “newly characterized antigen” test “allowed “patentees to claim antibodies by describing something that is not the invention, i.e., the antigen.” The CAFC has now found that such functionally limited mAb claims which describe the antigen binding target but not the mAb itself also fail the “enablement” requirement of 35 USC 112 (Amgen v. Sanofi, CAFC 20-1074 (2021)). In brief, the CAFC held that undue experimentation would be required to practice claims which encompass “millions of candidates claimed with respect to multiple specific functions” where “it would be necessary to first generate and then screen each candidate antibody to determine whether it meets the double-function claim limitations” (Id.).

The two Amgen v. Sanofi decisions thus effectively bar claims to mAb which are limited solely by functional attributes (i.e., their ability to bind an antigen or other ligand). While mAb can be claimed based on the amino acid sequences of their complementarity-determining regions (“CDRs”), such claims do not exclude use of other routinely obtainable mAb with wholly distinct CDRs which bind the same antigen and may not even exclude use of a competitor’s mAb comprising an amino acid substitution in one of the CDR’s.

Patent applicants can nonetheless consider alternative strategies for securing at least some claim breadth for their mAb inventions in light of the Amgen v. Sanofi decisions. For example, claims drawn to CDR sequences having one or more particular amino acid substitutions can be pursued provided that such substitutions are described and enabled by the application. Claims drawn to amino acid substitutions in CDRs can be pursued by reciting CDR sequences with particular substitutions in particular residues or more broadly by reciting percent identity limitations. The ultimate fate of such claims in the US will hinge in part on providing sufficient disclosure of such variant CDR sequences in the application. In contrast, the European Patent Office’s (EPO) recently updated guidelines for antibody patenting provide for solely functional antigen binding limitations, structural limitations that include percent sequence identity, combinations of functional and structural limitations, and even product-by-process limitations (e.g., mAb made by use of a particular antigen). Even if broader antibody claims are not ultimately patentable in the US, they could be pursued in Europe provided that the claims meet the EPO’s inventiveness requirement for a surprising technical effect.

Methods claims where a novel and non-obvious antigen is used to obtain a mAb can also be pursued in both the US and abroad. While such methods claims would not read on the mAb itself, they could potentially read on the activities of competitors who could otherwise obtain functionally equivalent mAb with different CDR sequences by simply using the same or equivalent antigen. Useful methods claims will need to encompass a reasonable range of equivalent antigens while avoiding any prior art where all or part of a therapeutic target protein comprising the antigen was used to generate a mAb.

It remains to be seen if the Courts or the USPTO Patent Trial and Appeal Board extend the Amgen v. Sanofi decisions to biological molecules other than antibodies claimed in whole or in part by their binding or other functional characteristics. After the Amgen v. Sanofi 2017 decision, the USPTO guidance memo to the patent examiners was limited to examination of antibody claims. Any subsequent USPTO guidance to examiners on the Amgen v. Sanofi 2021 decision could be closely monitored for any sign that new leadership at the USPTO will extend their guidance beyond examination of antibody claims for enablement.

Charles P. Romano, Ph.D. is a Senior Patent Agent in the MVS Biotechnology & Chemical Practice Group. To learn more, visit our MVS website, or contact Charley directly via email.

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