Regeneron Pharmaceuticals, Inc. v. Merus N.V., No. 16-1346 (Fed. Cir. 2017)Annotate this Case
Regeneron accused Merus of infringing the 018 patent. The district court issued an opinion construing various terms and declared one term indefinite. Merus asserted a counterclaim of unenforceability due to inequitable conduct. It argued that during prosecution of the patent, Regeneron’s patent prosecutors withheld four references that were cited in a third-party submission in related U.S. patent prosecution and in European opposition briefs, were but-for material, and were withheld by Regeneron with the specific intent to deceive. There was no dispute that Regeneron knew of the Withheld References during prosecution. Regeneron argued that the references were not but-for material, that they were cumulative of references actually relied-on during prosecution, and that Regeneron did not have any specific intent to deceive. The Federal Circuit affirmed the district court, which had “exhaustively detailed Regeneron’s discovery misconduct" throughout the litigation and sanctioned Regeneron by drawing an adverse inference of specific intent to deceive the PTO. The court noted Regeneron’s repeated violations of discovery orders and improper secreting of relevant and non-privileged documents. Regeneron committed inequitable conduct, rendering the patent unenforceable.