The front of U.S. Supreme Court in Washington, D.C. [Adobe stock photo]
However, Justice Elena Kagan, in her opinion for the majority, did say that the doctrine has limits.
The convoluted case involves the NovaSure system for abnormal uterine bleeding that Csaba Truckai invented in the late 1990s, filing for a patent assigned to his company Novacept. Hologic eventually acquired Novacept in 2007 and got claims added to the patent in 2015. Months later, Hologic sued Minerva Surgical — the new company Truckai had founded — for patent infringement. Minerva Surgical makes the Minerva Endometrial Ablation System, touted as an improved device to treat abnormal uterine bleeding.
In its arguments against the Hologic suit, Minerva said the newly added claim did not match NovaSure’s written description, which addresses applicator heads that are water permeable. The Minerva system has a moisture-impermeable applicator head so that it doesn’t remove any fluid during treatment.
Kagan found that the Federal Circuit erred because it did not consider whether Hologic expanded the patent claims to such an extent that it could no longer make an assignor estoppel argument against Truckai and Minerva. Instead, the Federal Circuit upheld a U.S. District Court for Delaware finding that assignor estoppel barred Minerva’s invalidity defense; the jury in the lower court case had awarded Hologic nearly $5 million in 2018.
“Assignor estoppel, we now hold, is well-grounded in centuries-old fairness principles, and the Federal Circuit was right to uphold it,” Kagan said in today’s opinion. “But the court failed to recognize the doctrine’s proper limits. The equitable basis of assignor estoppel defines its scope: The doctrine applies only when an inventor says one thing (explicitly or implicitly) in assigning a patent and the opposite in litigating against the patent’s owner.”
The case goes back to an appeals court, which will have to determine whether Hologic’s new claim is broader than the ones Truckai assigned.
