Assignor Estoppel Cannot Resurrect Patent Invalidated in an IPR, but it Can Save Patent from Challenge in District Court

In Hologic, Inc. v. Minerva Surgical, Inc.. [2019-2054, 2019-2081] (April 22, 2020), the Federal Circuit affirmed the district court’s determination that assignor estoppel does not bar the assignor from relying on our court’s affirmance of the Patent Trial and Appeal Board’s final decision invalidating the asserted patent claims in an inter partes review proceeding. and the district court’s determination summary judgment that assignor estoppel bars the assignor from asserting invalidity of the assigned second patent in district court.

Hologic and Cytyc sued Minerva Surgical for infringement of certain claims of its U.S. Patent Nos. 6,872,183 and 9,095,348, which relate to procedures and devices for endometrial ablation. Truckai invented the technology assigned the patents to NovaSure, which was later acquired by Cytyc. Truckai left NovaSure to found went on to found Minerva and develop competing technology. Minerva file IPRs as to both patents, but only the IPR against the ‘183 patent was instituted, the finding that the claims were unpatentable was affirmed by the Federal Circuit. The district court declined to award damages or an injunction as to the ‘183 patent, because it was invalidated. The district court awarded damages for infringement of the ‘358 patent.

The Federal Circuit examined the history of assignor estoppel, and noted that it has its limitations, noting that although estopped parties “cannot challenge the validity of” the patent at issue, “assignor estoppel does not limit their ability to defend themselves in other ways,” including “arguing that the patentee is itself collaterally estopped from asserting a patent found invalid in a prior proceeding.” Based on our precedent and the limits it places on the assignor estoppel doctrine, the Federal Circuit concluded that assignor estoppel does not preclude Minerva from relying on the Ho-logic decision to argue that the ’183 patent claims are void ab initio.

The Federal Circuit was mindful of the seeming unfairness to Hologic in this situation, pointing out that although Minerva would have been estopped from challenging the validity of the ’183 patent claims in district court, it was able to challenge their validity in an IPR proceeding and, hence, circumvent the assignor estoppel doctrine. Minerva had the right to do so under the AIA and Federal Circuit precedent. While the Federal Circuit understood Hologic’s predicament, it nevertheless concluded that the district court did not abuse its discretion in denying Hologic its requested injunctive and monetary relief following a finding of patent infringement of the ‘183 patent.

As to the ‘348 patent, the Federal Circuit declined Minerva’s invitation to “abandon the doctrine” of assignor estoppel entirely. Although recognizing that assignor estoppel is not a broad equitable device susceptible of automatic application, the Federal Circuit agreed with the district court that the equities weigh in favor of its application in this case. The Federal Circuit found the facts analogous to those in Diamond Scientific, Shamrock, and other cases in which an inventor executes broad assignments to his employer, leaves his employer, founds or takes on a controlling role at a competing company, and is directly involved in the alleged infringement.

Because the district court did not abuse its discretion in applying the doctrine of assignor estoppel, the Federal Circuit affirmed the district court’s grant of summary judgment of no invalidity as to the ’348 patent.