No Shenanigans: IPRs and Interference Estoppel
Contributed by Knobbe Martens. Originally published on Patexia; republished here as part of the LexDana archive.
Written by: Jacob R. Rosenbaum and Alistair J. McIntyre
Before Prost, Reyna, and Taranto. Appeal from the Patent Trial and Appeal Board (PTAB).
Summary: Interference estoppel does not apply when the interference was terminated due to a threshold issue.
Zynga petitioned for inter partes review (IPR) of an IGT patent after having attacked the same patent via an interference proceeding. IGT opposed, arguing interference estoppel under 37 C.F.R. § 41.127(a)(1). Because the interference proceeding was terminated on a threshold issue and the IPR petition relied on a combination of prior art references not used in the interference proceeding, the PTAB declined to apply interference estoppel. The PTAB ultimately concluded that IGT’s claims were obvious. IGT appealed.
The Federal Circuit affirmed, finding that the decision not to apply interference estoppel was related to the decision to institute the IPR and therefore unreviewable. The court reasoned that the PTO Director is afforded discretion regarding whether to institute an IPR. The decision to institute an IPR is generally unreviewable unless the PTO has violated legal constraints or engaged in other “shenanigans.”
The Federal Circuit found the PTAB’s reasoning for not applying interference estoppel sufficient to support a finding of no “shenanigans,” and that no exceptions applied to the general bar on reviewability of institution determinations. The court further affirmed the PTAB’s finding on obviousness.
Editor: Sean Murray
More insights
Fresh From the Bench: Latest Precedential Patent Case
Ridge Corp. et al. v. Kirk NationaLease Co. et al. , Appeal No. 2025-1254 (Fed. Cir. July 13, 2026) In its only precedential patent opinion last week, the Federal Circuit considered an appeal of a preliminary injunction issued by the U.S. District Court…
Fresh From the Bench: Latest Precedential Patent Cases
CASE OF THE WEEK Wyeth LLC v. AstraZeneca Pharmaceuticals LP , Appeal No. 2024-2325 (Fed. Cir. July 9, 2026) In our Case of the Week, the Federal Circuit affirmed a district court ruling reversing a $107.5 million jury verdict against AstraZeneca in a case…
Enanta Pharmaceuticals, Inc. v. Pfizer Inc., Appeal No. 2025-1427 (Fed. Cir. Jun. 23, 2026)
CASE OF THE WEEK Enanta Pharmaceuticals, Inc. v. Pfizer Inc., Appeal No. 2025-1427 (Fed. Cir. Jun. 23, 2026) In our Case of the Week, the Federal Circuit affirmed summary judgment invalidating all claims of Enanta’s Patent No. 11,358,953 as…