On Wednesday, the Federal Circuit held that while assignor estoppel is applicable in district court proceedings, petitions for inter partes review continue to not be subject to the equitable remedy.  Assignor estoppel is an equitable doctrine based on the principle of fair dealing that prevents a party who divests a patent from later challenging the validity of that patent.  The Federal Circuit’s precedential decision in Hologic, Inc. and Cytyc Surgical Products, LLC v. Minerva Surgical, Inc., Nos. 2019-2054, 2019-2081 (Fed. Cir. Apr. 22, 2020) highlights the potential unfairness from allowing the doctrine’s application in district court but not at the Patent Trial and Appeal Board (“PTAB”), and potentially presents an issue ripe for en banc review. 

In the 1990’s, Csaba Truckai founded NovaCept, a company that developed NovaSure, a medical device for detecting perforations in the uterus for endometrial ablations.  Mr. Truckai also invented U.S. Patent Nos. 6,872,183 (the “ʼ183 patent”) and 9,095,348 (the “ʼ348 patent”), assigned to NovaCept, that relate to procedures and devices for endometrial ablation.  NovaCept was acquired by Cytyc (along with the patents), which was then acquired by Hologic, the current assignee of the patents.  Mr. Truckai then founded Minerva, and developed the competing Endometrial Ablation System (“EAS”).

Hologic subsequently sued Minerva for infringement of the ʼ183 and ʼ348 patents.  Minerva alleged that the patents were invalid, and filed IPRs challenging both patents.  The Board denied institution on the ’348 patent, but found all challenged claims of the ’183 patent unpatentable.  The Board’s final written decision was upheld on appeal.

In district court, Hologic moved for summary judgment of no invalidity based on assignor estoppel.  The district court agreed that Mr. Truckai and Minerva were in privity such that assignor estoppel applies, and granted summary judgment of no invalidity.

On appeal, Hologic argued that assignor estoppel precludes Minerva from relying on the Federal Circuit’s decision upholding the results of the IPR to escape liability at the district court.  Hologic argued that an IPR’s final outcome is irrelevant to the parallel district court proceeding.  The Federal Circuit was not persuaded.  While acknowledging the “seeming unfairness” under the AIA and Federal Circuit precedent, Minerva was entitled to “circumvent the assignor estoppel doctrine” by challenging the validity of the ʼ183 patent in an IPR proceeding, which is not subject to equitable remedies.  The Federal Circuit found that the language of the statute—35 U.S.C. § 311(a)—was unambiguous in that it allows “a person who is not the owner of the patent” to file an IPR, including previous owners.  The Federal Circuit’s decision to affirm the Board’s invalidity determination “is dispositive of the validity of the ’183 patent claims, regardless of how the validity question came to this court, and regardless of whether assignor estoppel bars Minerva from challenging the patent’s validity in this district court case.”  And, because the ’183 patent claims are invalid, “Hologic cannot assert claims or seek ongoing monetary or injunctive relief based on infringement.” 

The Federal Circuit quickly dismissed Minerva’s multi-faceted attempt to escape assignor estoppel at the district court, finding that the present case is appropriate for assignor estoppel, and that the claims were prosecuted after assignment was of no moment.  The Federal Circuit addressed this latter issue in Diamond Scientific, holding irrelevant that at the time of assignment the patent applications were still pending and that the assignee may have later amended the claims. 

In light of this decision, en banc review may be necessary to address discrepancies in the application of assignor estoppel in district court cases and proceedings before the PTAB.  Judge Stoll seemingly agrees, writing separately:  “Given the odd circumstance created in this case, I suggest that it is time for this court to consider en banc the doctrine of assignor estoppel as it applies both in district court and in the Patent Office.  We should seek to clarify this odd and seemingly illogical regime in which an assignor cannot present any invalidity defenses in district court but can present a limited set of invalidity grounds in an IPR proceeding.”   

Until then, patent purchasers must effectively contract for protection that the law does not provide: prohibit former patent owners and inventors from using IPRs to challenge patents once they have been assigned.