Filing a petition for inter partes review (“IPR”) is a standard part of the playbook for defendants in patent litigation. One of the few risks for a petitioner is estoppel under 35 U.S.C. § 315(e)(2), which prohibits a petitioner who is unsuccessful on the merits from raising in district court “any ground that the petitioner raised or reasonably could have raised during that inter partes review.” By rule, a petitioner can only assert patents or printed publications as prior art in an IPR.
