Enanta Pharmaceuticals, Inc. filed a current report on October 29, 2026, disclosing that the Unified Patent Court of the European Union ruled European Patent No. EP 4 051 265 invalid and found Enanta's infringement action against Pfizer unfounded.

Key Highlights

  • UPC decision dated October 29, 2026: The Unified Patent Court concluded that European Patent No. EP 4 051 265 is invalid.
  • Infringement action dismissed: The UPC determined the infringement action was unfounded in light of its ruling on validity.
  • Defendant: The action had been filed against Pfizer Inc. and certain of its subsidiaries.
  • Product at issue: Pfizer's Paxlovid (nirmatrelvir tablets; ritonavir tablets) was the subject of the infringement claim.
  • Geographic scope: The action covered the 18 EU member states participating in the UPC.
  • Hearing date: A hearing on the infringement action and Pfizer's counterclaim for revocation was held on September 29, 2026.
  • Counterclaim: Pfizer had counterclaimed for revocation of the '265 Patent.

UPC Rules Against Enanta in Paxlovid Patent Dispute

According to the filing, Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA) had previously filed a patent infringement action in the Unified Patent Court of the European Union against Pfizer Inc. and certain of its subsidiaries. The action sought a determination of liability for infringement of European Patent No. EP 4 051 265 in connection with Pfizer's manufacture, use, and sale of Paxlovid (nirmatrelvir tablets; ritonavir tablets) across the 18 EU member states participating in the UPC.

The filing disclosed that Pfizer responded with a counterclaim seeking revocation of the '265 Patent. A hearing addressing both the infringement action and the counterclaim for revocation was held on September 29, 2026. On October 29, 2026, the UPC released its decision, which, according to the filing, concluded that the '265 Patent is invalid. The court also determined that the infringement action was "unfounded in light of its decision on validity," as stated in the filing.

The report was signed by Jay R. Luly, Ph.D., President and Chief Executive Officer of Enanta Pharmaceuticals, Inc., on October 29, 2026. No additional financial figures, next steps, or appeal information were included in the filing.

What Was Disclosed

Enanta Pharmaceuticals reported that the Unified Patent Court ruled European Patent No. EP 4 051 265 invalid and dismissed the company's infringement action against Pfizer regarding Paxlovid as unfounded, following a hearing held September 29, 2026.