In October 2021, Pfizer Inc. and four affiliated entities — PF Prism C.V., C.P. Pharmaceuticals International C.V., PBG Puerto Rico LLC, and PF PRISM IMB B.V. — filed suit against Sinotherapeutics Inc. in the U.S. District Court for the District of Delaware. The case, assigned to Judge Gregory B. Williams, centered on US9937181B2, a patent covering tofacitinib citrate extended-release tablet formulations marketed as Xeljanz XR 11 mg. The action was a classic Hatch-Waxman ANDA infringement dispute, triggered by Sinotherapeutics’ effort to bring a generic version of the branded extended-release product to market.

After 1,093 days, the parties filed a joint stipulation under Fed. R. Civ. P. 41(a)(1)(A)(ii) dismissing all claims and counterclaims without prejudice. The dismissal order explicitly preserved any protective orders entered during the litigation, waived appellate rights from the order itself, and confirmed that the Delaware District Court retains jurisdiction to enforce the underlying settlement agreement. The ‘without prejudice’ designation means Pfizer is not barred from reasserting these patent claims against Sinotherapeutics in the future, though the retention of settlement jurisdiction strongly suggests a negotiated resolution governs the parties’ ongoing relationship.

The approximately three-year litigation timeline is consistent with the typical pace of complex Hatch-Waxman proceedings in Delaware, though the absence of a merits judgment leaves the validity and infringement questions publicly unresolved. The court’s retained jurisdiction over the settlement agreement suggests terms were agreed that may govern Sinotherapeutics’ market entry timeline, royalty obligations, or other commercial conditions — none of which are visible in the public record. What drove the parties to resolve rather than litigate to judgment remains unknown, but the mutual cost-bearing arrangement suggests neither side perceived a decisive advantage at the time of dismissal.