Amgen Inc. v. Coherus Biosciences Inc., No. 18-1993 (Fed. Cir. 2019)Annotate this Case
Recombinant therapeutic proteins are a class of biologic medicines that are manufactured inside living cells. Before a protein can be therapeutically useful, it must first be purified from contaminants. Amgen’s patent claims methods of purifying proteins using hydrophobic interaction chromatography. Amgen sued Coherus for infringing the patent under the doctrine of equivalents because the salt combination used in Coherus’s process did not match any of the three expressly claimed salt combinations in the Amgen patent. The Federal Circuit affirmed the dismissal of the suit, reasoning that prosecution history estoppel bars Amgen from succeeding on its infringement claim under the doctrine of equivalents. During prosecution of the patent, Amgen clearly and unmistakably surrendered salt combinations other than the particular combinations recited in the claims.