
Reminder: Estoppel May Not Preclude Prior-Art Systemsm PTAB Litigation Blog
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The estoppel statute precludes a defendant who has challenged a claim in an IPR reaching final written decision from later challenging that claim on any ground that it raised or reasonably could have raised during the IPR proceedings. 35 U.S.C. § 315(e)(2). The boundaries of that rule were recently tested when a defendant asserted invalidity arguments before the district court in the Western District of Texas involving prior art systems in combination with prior art references that had been raised in the related IPR. CliniComp Int’l, Inc. v. Athenahealth, Inc., No. A-18-CV-00425-LY, 2020 WL 7011768 (W.D. Tex. Oct. 28, 2020).