European patent court rules Enanta patent invalid in Paxlovid suit against Pfizer

The ruling

The Unified Patent Court of the European Union ruled on October 29, 2026 that European Patent No. EP 4 051 265, the '265 Patent held by Enanta Pharmaceuticals, Inc. (Nasdaq: ENTA), is invalid. The company's own 8-K, filed the same day under Item 8.01, reports the decision and says the court also found the infringement action unfounded in light of the validity ruling. The defendants are Pfizer Inc. and certain of its subsidiaries. Enanta filed the infringement action against them in the court, seeking a finding of liability for the manufacture, use and sale of Paxlovid (nirmatrelvir tablets; ritonavir tablets) in the 18 EU member states that take part in the court. The 8-K does not list the individual subsidiaries. Pfizer counterclaimed for revocation of the patent. The court heard both the infringement action and the counterclaim on September 29, 2026. The 8-K does not say whether Enanta plans to appeal, and it does not state the damages sought or any financial effect of the decision. It is signed by Jay R. Luly, Ph.D., President and Chief Executive Officer.

What the company is built on

Enanta is a Delaware company based in Watertown, Massachusetts. Its 10-K for the fiscal year ended September 30, 2025 says it discovered glecaprevir, the second of two antiviral protease inhibitors it discovered and developed with AbbVie for chronic hepatitis C virus infection. Glecaprevir is co-formulated in AbbVie's MAVYRET (U.S.) and MAVIRET (ex-U.S.) treatments, marketed since 2017. The 10-K says MAVYRET was also approved as the first and only treatment for acute hepatitis C infection in June 2025.

The financial picture

For fiscal 2025, the 10-K filed on November 19, 2025 reports a net loss of $81,889 thousand, against $116,045 thousand in fiscal 2024, or $3.84 per share against $5.48 on weighted average shares of 21,336 thousand. Research and development expense was $106.7 million, against $131.5 million. Net cash used in operating activities was $19,272 thousand, against $78,764 thousand. Stockholders' equity fell to $64,717 thousand at September 30, 2025, from $128,814 thousand a year earlier. The accumulated deficit reached $404,929 thousand, from $323,040 thousand. The company also made payments on a royalty sale liability of $26,486 thousand in fiscal 2025 and $27,479 thousand in fiscal 2024. Cash, cash equivalents and restricted cash were $35,658 thousand at September 30, 2025, down from $41,201 thousand a year earlier, a decline of $5,543 thousand. Net cash provided by investing activities was $40,347 thousand, reflecting sales and maturities of marketable securities. The cash flow statement also shows a $31,999 thousand change in income tax receivable as an adjustment to the net loss, which helped narrow the gap between the loss and the cash used in operations. The fiscal 2025 loss is smaller than the year before, but stockholders' equity fell. Those reported figures cover periods before the decision. The 8-K says the court found the infringement action unfounded in light of its ruling on validity, so the claim Enanta brought against Pfizer in the EU did not succeed at this stage.

What comes next

The 8-K says nothing about an appeal or a timeline for one, and it gives no date for any further step in the case.

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