US 11358953

Here's a concise summary of US patent 11358953, including details and its current litigation status:

US Patent 11358953 Summary

• Title: Functionalized peptides as antiviral agents
• Assignee: Enanta Pharmaceuticals Inc.
• Inventors: Joseph D. Panarese, Dexter Davis, Nathaniel Thomas Kenton, Samuel Bartlett, Sean M. Rafferty, Yat Sun Or
• Filing Date: November 9, 2021
• Issue Date: June 14, 2022
• Abstract: The patent discloses compounds of Formula (I), and their pharmaceutically acceptable salts, which are intended to inhibit coronavirus replication activity. The invention also covers pharmaceutical compositions containing these compounds and methods for treating or preventing coronavirus infections in a subject by administering a therapeutically effective amount of such a compound or salt thereof.

CAFC 2026 Dockets / Current Legal Status:

As of June 23, 2026, the U.S. Court of Appeals for the Federal Circuit (CAFC) has affirmed a lower court's decision, ruling that all claims of Enanta Pharmaceuticals Inc.'s U.S. Patent 11,358,953 are invalid. The case, Enanta Pharmaceuticals, Inc. v. Pfizer Inc., centered on whether the patent could claim priority from its earlier provisional application. The CAFC concluded that the provisional application lacked adequate written description support under 35 U.S.C. Section 112 for a key chemical substituent (specifically, a C1-alkyl group, where the provisional disclosed C2-C12 alkyl groups). This meant the patent could not claim the earlier priority date and was anticipated by Pfizer's prior public disclosure of nirmatrelvir (a component of Paxlovid, which contains a one-carbon alkyl group) in April 2021. Therefore, the claims of US11358953 have been declared invalid.

Plain-Language Overview of Independent Claims (Noting Invalidity):

Despite the claims being ruled invalid, here's a plain-language overview of the independent claims as they appear in the patent:

• Independent Claim 1: This claim describes a compound with a specific chemical structure (Formula (I)) and its pharmaceutically acceptable salts, N-oxides, esters, and prodrugs. This compound is characterized by various functional groups (A, L1, L2, X, Q, R11, R12, R13, R14, R15, R16) and their allowed variations and substitutions. The core structure involves a series of linked amino acid-like components, including a heterocyclic ring and a terminal group 'X' which can be a nitrile, various carbonyl-containing groups, or other specified functionalities. The overall intent is to define a class of functionalized peptides.

  • Uncertainty Note: Given the CAFC decision, the legal enforceability and validity of this claim, and all others dependent on it, are nullified. The dispute specifically revolved around the scope of an "optionally substituted -C1-C6 alkyl" definition in the context of the provisional application's disclosure of "C2-C12 alkyl".

• Independent Claim 13: This claim describes a pharmaceutical composition. It specifies that this composition must include a therapeutically effective amount of the compound as defined in Claim 1 (or any of claims 2-12, which are dependent on Claim 1) and at least one pharmaceutically acceptable carrier or excipient.

  • Uncertainty Note: As it depends on the validity of Claim 1, this claim for a pharmaceutical composition is also invalid due to the CAFC ruling.

• Independent Claim 14: This claim outlines a method for treating or preventing a coronavirus infection in a subject. The method involves administering to the subject a therapeutically effective amount of a compound as defined in Claim 1 (or any of claims 2-12).

  • Uncertainty Note: Similarly, this method claim is invalid because it relies on the compounds defined in Claim 1, which have been ruled invalid by the CAFC.

• Independent Claim 22: This claim specifies a method of inhibiting coronavirus 3C-Like protease (3CLpro) activity. It involves contacting the 3CLpro with a therapeutically effective amount of a compound as defined in Claim 1 (or any of claims 2-12).

  • Uncertainty Note: This method claim is also invalid, as it hinges on the use of the compounds defined in Claim 1, which are invalid.

• Independent Claim 23: This claim describes a method for treating a respiratory disorder in a subject. It involves administering to the subject a therapeutically effective amount of a compound as defined in Claim 1 (or any of claims 2-12).

  • Uncertainty Note: This method claim is invalid, directly depending on the validity of the compounds in Claim 1.