Argument-based Estoppel May Limit Doctrine of Equivalents Even if Arguments Were Not Required to Secure Allowance

In Amgen Inc. v. Coherus Biosciences Inc., No. 2018-1993 (July 29, 2019), the Federal Circuit determined that argument-based estoppel limited the scope of claims asserted in an infringement suit, resulting in a finding of non-infringement under the doctrine of equivalents.   The Federal Circuit reasoned that argument-based estoppel may apply to “assertions made during prosecution in support of patentability, whether or not actually required to secure allowance of the claim.”  The Federal Circuit found that the patentee’s reliance on “particular combinations” of salts in arguments made to distinguish over the prior art limited the claim scope to the recited combinations of salts.  Further, the Federal Circuit found that because the “particular combinations” argument and other arguments made by the patentee could be applied independently to determine whether estoppel applied, the other arguments made in the response with the “particular combinations” argument, and those made in a subsequent response, did not alter the analysis.

Slip opinion available at