UPC invalidates Enanta's EP 4 051 265 patent; Paxlovid infringement action against Pfizer dismissed

ENANTA PHARMACEUTICALS INC

• Unified Patent Court ruled on October 29, 2026 that European Patent No. EP 4 051 265 is invalid, and that Enanta's infringement action was unfounded in light of that holding.
• Enanta had sued Pfizer and subsidiaries in the UPC over Pfizer's manufacture, use and sale of Paxlovid (nirmatrelvir/ritonavir tablets) across the 18 EU member states participating in the UPC.
• Pfizer counterclaimed for revocation of the '265 Patent; a hearing on both the infringement action and the revocation counterclaim was held September 29, 2026.
• The decision removes Enanta's asserted European patent claims against Paxlovid in the UPC jurisdiction, with no injunction or damages awarded to Enanta.