---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-437774"
form_type: "8-K"
ticker: "ENTA"
cik: "0001177648"
company_name: "ENANTA PHARMACEUTICALS INC"
filed_at: "2026-10-29T20:05:15+00:00"
generated_at: "2026-10-29T20:06:17.486549+00:00"
event_type: "litigation"
sentiment: "negative"
materiality_score: 0.6
calibrated_materiality_score: 0.6
confidence: "high"
source: SEC EDGAR
---

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

## Summary
- 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.

## SEC filing metadata
- accession: 0001193125-26-437774
- form_type: 8-K
- ticker: ENTA
- cik: 0001177648
- company_name: ENANTA PHARMACEUTICALS INC
- filed_at: 2026-10-29T20:05:15+00:00
- event_type: litigation
- sentiment: negative
- materiality_score: 0.6
- calibrated_materiality_score: 0.6
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1177648/000119312526437774/0001193125-26-437774-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1177648/000119312526437774/enta-20261029.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-437774
- JSON: https://secwatch.observer/filing/0001193125-26-437774.json
- Plain text: https://secwatch.observer/filing/0001193125-26-437774.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.