IGT v. Zynga Inc., No. 2023-2262 (Fed. Cir. (PTAB) July 22, 2025). Opinion by Taranto, joined by Prost and Reyna.
IGT owns a patent related to secured virtual networks in gaming environments. After the patent application was published, Zynga filed an application that copied claims from IGT’s application, prompting the Board of Patent Appeals and Interferences to declare an interference proceeding.
In the interference proceeding, Zynga moved for judgment that the claims were unpatentable as obvious, and IGT moved for judgment that Zynga lacked standing because the claims lacked sufficient written description. The Board agreed with IGT and granted judgment on IGT’s “threshold issue” of written description, finding that the claims of Zynga’s application lacked adequate written-description support. Accordingly, the Board terminated the interference proceeding and dismissed “as moot” Zynga’s obviousness arguments.
A decade later, IGT sued Zynga for infringement of the same patent whose application had been at issue in the interference proceeding. Zynga then filed an IPR petition asserting that the claims would have been obvious based on prior art not involved in the interference. In response, IGT argued that the Board should deny institution of the IPR because of interference estoppel under 37 C.F.R. § 41.127(a)(1), which provides that “a[n interference] judgment disposes of all issues that were, or by motion could have properly been, raised and decided.”
The Board instituted the IPR and rejected IGT’s interference estoppel arguments for two reasons. First, “because it had terminated the interference based on the ‘threshold issue’ of lack of adequate written support,” the Board held that it did not decide any issues of unpatentability in the interference proceeding. Second, the Board held that “to the extent the estoppel regulation [] contained in the interference regulations even ‘applies’ to the IPR, the Board waived application of the regulation.”
The PTO Director decided sua sponte to review the Board’s decision. The Director affirmed the institution decision because “interference estoppel did not apply” since IPR proceedings are governed by a federal regulation that does not incorporate the interference estoppel provisions of 37 C.F.R. § 41.127(a)(1). And even if interference estoppel applied to IPR proceedings, the Director held that interference estoppel would not apply here “because the Board’s termination [was] based on a threshold issue” rather than a determination on unpatentability. The Board eventually issued a Final Written decision finding the claims unpatentable as obvious, and IGT appealed.
The Federal Circuit affirmed. IGT first argued that the PTO erred in ruling that interference estoppel did not bar Zynga from petitioning for IPR. The Federal Circuit disagreed, concluding that “the PTO’s interference-estoppel determination in this case is within the general rule of unreviewability [for institution decisions and questions closely tied to such decisions], and in any event we see no reversible error in that determination that could justify an exception to that rule for this case,” such as “blatant violations of legal constraints or other ‘shenanigans.’” In the end, the court noted that IGT’s arguments were nothing more than “a challenge to institution,” which is not appealable.
The Federal Circuit also reviewed the Board’s determination that the challenged claims were unpatentable as obvious. IGT argued that the Board impermissibly adopted a new theory in finding the claims unpatentable because the Board cited new teachings not relied on by Zynga. IGT also argued that the Board erred by concluding that the prior art taught certain claim elements. The Federal Circuit rejected both arguments, noting that the Board properly considered and rejected IGT’s arguments about the prior art and that IGT had sufficient notice of the prior art’s teachings, as IGT had cited those teachings in its own papers.