Minerva v. Hologic: Assignor Estoppel Doctrine Retained, But Limited

• Published date: 18 August 2021
• Subject Matter: Intellectual Property, Litigation, Mediation & Arbitration, Patent, Trials & Appeals & Compensation
• Law Firm: Haug Partners
• Author: Mr Jonathan Herstoff and Chinmay Bagwe

On June 29, 2021, the Supreme Court in a 5-4 decision¹ retained the doctrine of assignor estoppel.² However, the Court also held that "the Federal Circuit has applied the doctrine too expansively."³ Accordingly, the Supreme Court clarified that assignor estoppel bars the assignor of a patent from challenging the validity of that patent only when "the assignor's claim of invalidity contradicts explicit or implicit representations he made in assigning the patent."⁴ The Court provided three examples of situations in which the doctrine of assignor estoppel would not apply: (1) "when an assignment occurs before an inventor can possibly make a warranty of validity as to specific patent claims", (2) "when a later legal development renders irrelevant the warranty given at the time of assignment", and (3) when a "post-assignment development'a change in patent claims'can remove the rationale for applying assignor estoppel."⁵ The Supreme Court remanded the case to the Federal Circuit for further proceedings because the Federal Circuit "failed to recognize [these] boundaries."⁶

I. Background

Hologic, Inc, and Cytyc Surgical Products, LLC (collectively, "Hologic") sued Minerva for infringement of U.S. Patent Nos. 6,872,183 and 9,095,348, which cover an apparatus and methods for endometrial ablation.⁷ Both the '183 and '348 patents list Csaba Truckai as an inventor.⁸

In 1993, Truckai co-founded NovaCept, Inc.⁹ In the late 1990s, Truckai and his design team developed the NovaSure system, a medical device that treats menorrhagia.¹⁰ Truckai/NovaCept filed patent applications covering the NovaSure system, from which the'183 and '348 patents would later claim priority.¹¹ Truckai assigned his broad interest in the patent applications to NovaCept.¹² In 2004, Cytyc Corporation acquired NovaCept for $325 million.¹³ NovaCept assigned all patent rights to Cytyc.¹⁴ Thereafter, Hologic acquired Cytyc in 2007.¹⁵ Hologic is the current assignee of the'183 and '348 patents, which were issued in 2005 and 2015 respectively.¹⁶

Meanwhile in 2008, Truckai founded Minerva, where he developed the Endometrial Ablation System ("EAS").¹⁷ In 2015, EAS received FDA approval for the same indication as Hologic's NovaSure system.¹⁸ Shortly after, Minerva began commercially distributing EAS, which gave rise to the lawsuit.¹⁹

II. District Court

In November 2015, Hologic sued Minerva in Delaware District Court, alleging infringement of certain claims of the '183 and '348 patents.²⁰ Minerva asserted that the claims were invalid for lack of adequate written description and lack of enablement.²¹ Both parties moved for summary judgment on the issue of validity.²² Hologic argued that assignor estoppel bars Minerva from challenging invalidity.²³ Minerva contended that "all of the asserted claims are invalid for failure to meet the written description and enablement requirements" because the claims go beyond the scope of what is described in the patents and "undue experimentation would be required to practice the invention."²⁴ The district court granted Hologic's motion on both patents and denied Minerva's motion.²⁵

"Considering the balance of equities and the relationship of Truckai to Minerva," the district court found "privity between Truckai and Minerva" and that "assignor estoppel applies to Minerva's defenses."²⁶ Specifically, the district court found that Truckai founded Minerva, developed the EAS, and "executed a broad assignment of his patent rights to NovaCept and later sold [it] to Hologic's predecessor for $325 million."²⁷ The district court also found that "Minerva's invalidity defenses [were] barred by assignor estoppel" and that "even if Minerva were not estopped from raising the defense," its motion "lack[ed] merit."²⁸ Minerva appealed to the Federal...