WATERTOWN, Mass. — Enanta Pharmaceuticals, Inc. has filed a patent infringement lawsuit against Pfizer Inc. and its subsidiaries in the Unified Patent Court (UPC) of the European Union, alleging that Pfizer’s manufacture and sale of its COVID-19 antiviral treatment Paxlovid violates Enanta’s newly granted European patent.
The action, filed under case number 35071/2025, seeks a determination of liability related to European Patent No. EP 4 051 265, which covers coronavirus protease inhibitors invented by Enanta scientists. The patent, granted and published in the European Patent Bulletin this week, stems from a July 2020 application and is the European counterpart to U.S. Patent No. 11,358,953, which is already the subject of ongoing litigation between Enanta and Pfizer in the United States.
The lawsuit targets Pfizer’s activities in the 18 EU countries currently participating in the UPC system. Under UPC procedures, a hearing on the infringement action is expected within 12 months, with a decision issued within weeks afterward. If infringement is found, additional proceedings would determine damages.
All timelines, the company noted, remain subject to potential appeals and other customary steps in European patent litigation.
