Pfizer Sued by Enanta Over Patent Infringement for COVID Pill in EU

Enanta Pharmaceuticals has filed a lawsuit against Pfizer in the EU, alleging that Pfizer's COVID-19 pill, Paxlovid, infringes on Enanta's European patent rights. The lawsuit claims that Pfizer violated Enanta's rights by developing and marketing Paxlovid without permission. The case is related to Enanta's European patent for a class of protease inhibitors, which Pfizer allegedly used in Paxlovid.

Enanta Pharmaceuticals, Inc. (NASDAQ: ENTA), a clinical-stage biotechnology company, has filed a lawsuit against Pfizer Inc. in the Unified Patent Court (UPC) of the European Union. The suit, action number 35071/2025, alleges that Pfizer's COVID-19 antiviral, Paxlovid™, infringes on Enanta's European patent rights. Enanta claims that Pfizer developed and marketed Paxlovid without permission, using a class of protease inhibitors covered by Enanta's European Patent No. EP 4 051 265 (the '265 Patent).

Enanta's patent was granted by the European Patent Office and is based on a July 2020 patent application describing coronavirus protease inhibitors. The '265 Patent is the European counterpart of U.S. Patent No. 11,358,953 (the '953 Patent), which is currently involved in ongoing U.S. litigation between Enanta and Pfizer. The enforcement action targets Pfizer's activities in the 18 countries of the European Union participating in the UPC.

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 focused on developing small molecule drugs for viral infections and immunological diseases. The company's 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 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 contributes ongoing funding to Enanta's operations.

Enanta cautions investors not to place undue reliance on forward-looking statements contained in this release. These statements speak only as of the date of this release, and Enanta undertakes no obligation to update or revise these statements, except as may be required by law.

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