[co-author: Megan Mahoney]

A judge in the Eastern District of Virginia recently held that cancellation of independent claims in an inter partes review (IPR) did not preclude the plaintiff from asserting infringement based on the doctrine of equivalents for surviving dependent claims. The district court found that, as a matter of law, amendment-based prosecution history estoppel does not apply based on the Patent Trial and Appeal Board’s cancellation of all independent claims of the patent.

Plaintiff Columbia University asserted patent infringement against Defendant Norton’s antivirus software, including under the doctrine of equivalents. Defendant challenged the patents in an IPR, and the PTAB found unpatentable all independent claims of one of those patents. There was no motion to amend filed in the IPR. Later, in the district court, Defendant moved for partial summary judgment, arguing that amendment-based prosecution history estoppel forecloses a doctrine of equivalents argument related to the surviving dependent claims of that patent. Specifically, Defendant argued that cancellation of an independent claim to pursue dependent claims gives rise to a presumption of prosecution history estoppel. In response, Plaintiff noted that no court has ever applied amendment-based estoppel to the cancellation of independent claims in IPR proceedings.

The court explained that, under amendment-based estoppel, there is a presumption that a narrowing amendment made to achieve patentability during prosecution surrenders the entire subject matter—including any equivalents—between the original claim limitation and the amended claim limitation. Here, the court found that the mere fact of claim cancellation during IPR, without accompanying argument, could not give rise to amendment-based prosecution history estoppel. Accordingly, Plaintiff was not estopped by amendment-based estoppel from pursuing its infringement claim under a doctrine of equivalents theory.

Practice Tip: Patent owners seeking to assert infringement under the doctrine of equivalents should be mindful of possible estoppel resulting from patentability arguments and claim amendments. At least one court has found however, that mere cancellation of independent claims in an IPR will not preclude a doctrine of equivalents theory for remaining dependent claims.

Trustees of Columbia University in the City of New York v. NortonLifeLock Inc., 3-13-cv-00808 (E.D.V.A. Dec. 23, 2021)