Treatment of feline infectious peritonitis in cats with molnupiravir: Outcomes for 54 cases

Authors: TM Clark, SJ Coggins, R korman, J King, R Malik

Abstract:

Objective To evaluate the clinical applications and treatment outcomes using molnupiravir (MPV) for the treatment of naturally occurring feline infectious peritonitis. Methods , 92 client-owned cats with confirmed or presumptive FIP were retrospectively recruited from 35 veterinary practices between February 2023 and March 2024, primarily in Australia. Cats were categorised based on treatment received: Cohort A: Molnupiravir treatment: monotherapy, maintenance, and rescue therapy. Cohort B: Nucleoside analogue treatment: remdesivir and/or GS-441524. Seventy-eight cats were enrolled. Molnupiravir was administered orally for a median of 84 days, at a median dose of 13.3 mg/kg BID. Remission was defined as (i) the resolution of FIP-related clinical signs and normalisation of serum globulin concentrations and A:G ratio (to ≥0.6) or (ii) sustained clinical remission for at least 100 days post-treatment. Cure rate was defined as the percentage of cats achieving sustained remission, without requiring rescue therapy or experiencing a relapse event. Results Molnuparivir monotherapy resulted in a cure rate of 72% (13/18) while maintenance therapy resulted in a cure rate of 86% (25/29). Molnupiravir, utilised as rescue therapy, resulted in a cure rate of 100% (7/7). Treatment with remdesivir and/or GS-441524 resulted in a cure rate of 71% (17/24). Survival analysis revealed no significant difference in outcomes between cats treated with MPV monotherapy and those treated with nucleoside analogues. Adverse effects were uncommon but included neutropenia, and transient elevations in hepatic enzymes. Conclusion and Relevance In our study, molnupiravir demonstrated comparable outcomes to treatment with remdesivir and/or GS-441524 for treating FIP and serves as an accessible, effective option across various presentations, including ocular and neurological forms.

Keywords: FIP, molnupiravir, antiviral, nucleoside analogue