Efficacy of oral remdesivir in treating feline infectious peritonitis: a prospective observational study of 29 cats

ObjectivesThe primary aim of this prospective observational study was to document clinical progression, survival, remission and relapse in New Zealand cats with feline infectious peritonitis (FIP) that were treated with compounded oral remdesivir with or without initial parenteral remdesivir therapy. The secondary aims were to determine the optimal monitoring protocols and report the adverse effects of treatment and complications associated with FIP.MethodsA total of 29 client-owned cats with a clinical diagnosis of FIP were prospectively recruited. Cats were administered oral remdesivir (30 mg/kg q24h), rounded up to the nearest capsule size as the sole treatment, or after initial parenteral remdesivir (15-30 mg/kg q24h). Rechecks were recommended at weeks 1, 2, 4, 8 and 12 during treatment, and at 2 and 12 weeks after treatment. A full physical examination (including neurological and ophthalmic examination) and point-of-care ultrasound were performed at each recheck. A complete blood count and biochemistry panel were performed at weeks 4, 8, 12 and 24. Molnupiravir was offered as a rescue therapy for cats that relapsed.ResultsIn total, 25 (86%) cats entered remission and survived beyond 6 months (range 6-27). A total of 22 (75%) cats achieved remission within 84 days while receiving oral remdesivir. Three cats received subsequent molnupiravir rescue therapy to achieve remission. Five cats (20%) experienced relapse: four with non-effusive disease and one with effusive disease. Notably, 4/8 (50%) non-effusive cases relapsed, compared with only 1/20 (5%) with effusive disease.Conclusions and relevanceThis study demonstrates that oral remdesivir at a dose rate of 30 mg/kg q24h is an effective treatment for effusive FIP. The survival rate in non-effusive cats was significantly lower; therefore, an increased dose rate or frequency of administration should be considered in these cats. Oral remdesivir is a viable antiviral option where GS-441524 is unavailable.