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Enanta Pharmaceuticals Files Patent Infringement Suit Against Pfizer

Enanta Pharmaceuticals, Inc. (NASDAQ: ENTA), a clinical-stage biotechnology company dedicated to creating novel, small molecule drugs for viral infections and liver diseases, announced today that it has filed suit in United States District Court for the District of Massachusetts against Pfizer, Inc. seeking damages for infringement of U.S. Patent No. 11,358,953 (the ’953 Patent) in the manufacture, use and sale of Pfizer’s COVID-19 antiviral, Paxlovid™ (nirmatrelvir tablets; ritonavir tablets). The United States Patent and Trademark Office awarded the patent to Enanta earlier this month based on Enanta’s July 2020 patent application describing coronavirus protease inhibitors invented by Enanta scientists. The complaint can be accessed on Enanta’s website here.

Enanta recognizes the importance of Paxlovid’s availability to patients and does not intend to seek an injunction or take other action in this litigation that would impede the production, sale or distribution of Paxlovid. Enanta seeks fair compensation for Pfizer’s use of a coronavirus 3CL protease inhibitor claimed in the ‘953 patent.

About Enanta Pharmaceuticals, Inc.

Enanta is using its robust, chemistry-driven approach and drug discovery capabilities to become a leader in the discovery and development of small molecule drugs for the treatment of viral infections and liver diseases. Enanta’s research and development programs include clinical candidates currently in development for the following disease targets: respiratory syncytial virus (RSV), SARS-CoV-2 (COVID-19) and hepatitis B virus (HBV). Enanta is also conducting research in human metapneumovirus (hMPV).

Enanta’s research and development activities are funded by royalties from hepatitis C virus (HCV) products developed under its collaboration with AbbVie. Glecaprevir, a protease inhibitor discovered by Enanta, is part of one of the leading treatment regimens for curing chronic HCV infection and is sold by AbbVie in numerous countries under the tradenames MAVYRET® (U.S.) and MAVIRET® (ex-U.S.) (glecaprevir/pibrentasvir). Enanta’s antiviral clinical candidate for COVID-19 is a novel coronavirus 3CL protease inhibitor, also known as a main protease inhibitor, or Mpro, specifically designed as an oral treatment for COVID-19. Please visit for more information.

Forward Looking Statements Disclaimer

This press release contains forward-looking statements, including statements with respect to Enanta’s filing in the United States District Court for the District of Massachusetts of a suit against Pfizer, Inc. seeking damages for patent infringement and Enanta’s intentions with respect to further action with respect to such patent. Statements that are not historical facts are based on management’s current expectations, estimates, forecasts and projections about Enanta’s business and the industry in which it operates and management’s beliefs and assumptions. The statements contained in this release are not guarantees of future performance and involve certain risks, uncertainties and assumptions, which are difficult to predict. Therefore, actual outcomes and results may differ materially from what is expressed in such forward-looking statements. Important factors and risks that may affect actual results include: Enanta is competing to develop intellectual property in areas of small-molecule drug development that are highly competitive; issued patents, including those covering one or more of its product candidates, could be found invalid or unenforceable if challenged in court and could be costly to defend and be a distraction for Enanta’s senior management and scientific personnel; intellectual property litigation may lead to unfavorable publicity that harms Enanta’s reputation and causes the market price of its common stock to decline; and other risk factors described or referred to in “Risk Factors” in Enanta’s most recent Form 10-Q for the fiscal quarter ended March 31, 2022 and other periodic reports filed more recently with the Securities and Exchange Commission. Enanta cautions investors not to place undue reliance on the 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.


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