Minerva Surgical, Inc. v. Hologic, Inc.

Truckai, as the inventor and assignor, implicitly represented through his patent transfer to Hologic that the patent was valid, a representation on which Hologic relied when taking ownership and enforcing it against competitors. When Truckai later founded Minerva and challenged that same patent's validity as a defense to infringement, he sought to adopt a position directly inconsistent with his prior assignment, precisely the circumstance assignor estoppel addresses. The Court reaffirmed the doctrine applies in this context, where the assignor's business incentive to invalidate a patent he previously transferred creates an impermissible inconsistency, though it reserved narrow exceptions for purely formal assignments or challenges to claims added post-transfer.