Minerva Surgical, Inc. v. Hologic, Inc.

The decision in Westinghouse v. Formica Insulation Co., 266 U.S. 342, 350 (1924) provided that assignor estoppel is a principle of fairness. “If one lawfully conveys to another a patented right,” the Court reasoned, “fair dealing should prevent him from derogating from the title he has assigned.”

In 2015, Hologic sued Minerva alleging that Minerva’s Endometrial Ablation System (EAS) infringed certain claims of its patents. Minerva argued that the patents were invalid based on lack of enablement and failure to provide an adequate written description, and moreover were not patentable due to prior art. Hologic relied solely on the doctrine of assignor estoppel. Minerva’s main argument in this case is that assignor estoppel should be eliminated in its entirety. The decision in Westinghouse v. Formica Insulation Co., 266 U.S. 342 (1924) provided that assignor estoppel is a principle of fairness. “If one lawfully conveys to another a patented right,” the Court reasoned, “fair dealing should prevent him from derogating from the title he has assigned.” Id., at 350. The Court ruled that a Defendant in a patent infringement case who assigned the patent can be barred under the doctrine of assignor estoppel from asserting a defense of invalidity if the assignors claim contradicts the representation that the assignor made while assigning the patent. The Court vacates the judgment of the Federal Circuit Court and remands the case for further proceedings consistent with this opinion.