In Baxalta Inc. v. Genentech, Inc., No. 2019-1527 (Fed. Cir. Aug. 27, 2020), the Federal Circuit vacated antibody-related claim constructions, holding the district court erred by not considering the patent as a whole.

Baxalta, a unit of Takeda, sued Genentech alleging the blockbuster hemophilia treatment Hemlibra (emicizumab-kxwh) infringed U.S. Patent No. 7,033,590. The District of Delaware construed “antibody” to be limited to molecules with identical heavy chains and identical light chains, finding the specification defined the term, and “antibody fragment” to be limited to antibodies lacking a constant region and excluding bispecific antibodies, finding the prosecution history disclaimed a broader construction. Based on these constructions, the parties entered a stipulation of noninfringement. Baxalta appealed.

The Federal Circuit vacated the constructions and the stipulation of noninfringement. First, the Court took issue with the narrow constructions as they would render the asserted dependent claims invalid. Second, the Court found implausible that by mistake, the specification disclosed antibodies and techniques for preparing antibodies falling outside the narrow construction. Third, the Court rejected the district court’s application of prosecution history disclaimer, finding no clear disavowal language in the prosecution history. Because the stipulation of noninfringement was based on erroneous claim construction, the Court vacated and remanded.