Enanta Files Patent Infringement Suit Against Pfizer Over COVID-19 Antiviral Patent

Enanta has filed a patent infringement suit against Pfizer in the European Union's Unified Patent Court, seeking liability for Pfizer's use and sale of Paxlovid, a COVID-19 antiviral. The suit targets Pfizer's activities in 18 EU countries and is based on Enanta's patent application for coronavirus protease inhibitors. A hearing is expected within 12 months, with a decision to follow, and potential subsequent proceedings to determine damages.

Enanta Pharmaceuticals, Inc. (NASDAQ: ENTA), a clinical-stage biotechnology company, has filed a patent infringement suit against Pfizer Inc. in the European Union's Unified Patent Court (UPC). The suit, action number 35071/2025, seeks a determination of liability for Pfizer's use and infringement of European Patent No. EP 4 051 265 (the '265 Patent) in the manufacture, use, and sale of Pfizer's COVID-19 antiviral, Paxlovid™ (nirmatrelvir tablets; ritonavir tablets). The enforcement action targets Pfizer's activities in the 18 countries of the European Union currently participating in the UPC.

The '265 Patent, granted by the European Patent Office, is based on Enanta's July 2020 patent application describing coronavirus protease inhibitors invented by Enanta scientists. It is the European counterpart of U.S. Patent No. 11,358,953 (the '953 Patent), which is involved in ongoing U.S. litigation between Enanta and Pfizer Inc.

Under UPC procedures, a hearing on the infringement action is expected to occur within the UPC's published 12-month target, with the decision rendered within weeks thereafter. If the UPC determines there has been infringement, subsequent proceedings would be required to determine damages. All timelines remain subject to potential rights of appeal and other customary proceedings in European patent litigation.

Enanta Pharmaceuticals is dedicated to creating novel, small molecule drugs for viral infections and immunological diseases. Its clinical programs are currently focused on respiratory syncytial virus (RSV) and its earlier-stage immunology pipeline aims to develop treatments for inflammatory diseases by targeting key drivers of the type 2 immune response, including KIT and STAT6 inhibition. Glecaprevir, a protease inhibitor discovered by Enanta, is part of one of the leading treatment regimens for curing hepatitis C virus (HCV) infection and is sold by AbbVie in numerous countries under the tradenames MAVYRET® (U.S.) and MAVIRET® (ex-U.S.) (glecaprevir/pibrentasvir). A portion of Enanta’s royalties from HCV products developed under its collaboration with AbbVie contribute ongoing funding to Enanta’s operations.

Enanta's filing of this suit is part of its ongoing efforts to protect its intellectual property in the area of small-molecule drug development. The company cautions investors not to place undue reliance on forward-looking statements, as actual outcomes and results may differ materially from what is expressed in such statements.

References:
[1] https://www.businesswire.com/news/home/20250820282912/en/Enanta-Pharmaceuticals-Files-Patent-Infringement-Suit-Against-Pfizer-in-the-Unified-Patent-Court-of-the-European-Union
[2] https://www.marketscreener.com/news/enanta-pharmaceuticals-files-patent-infringement-suit-against-pfizer-in-the-unified-patent-court-of-ce7c51d2dd8df22c
[3] https://ir.enanta.com/news-releases/news-release-details/enanta-pharmaceuticals-files-patent-infringement-suit-against-0