FIP Treatment Outcomes

Matthew Kornya, DVM, DVSc, DACVIM, University of Guelph, Guelph, Ontario, Canada

ArticleLast Updated October 20233 min read
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In the Literature

Coggins SJ, Norris JM, Malik R, et al. Outcomes of treatment of cats with feline infectious peritonitis using parenterally administered remdesivir, with or without transition to orally administered GS-441524. J Vet Intern Med. 2023;37(5):1772-1783. doi:10.1111/jvim.16803

The Research …

FIP was considered fatal until the discovery of GC-376 and GS-441524, which can be used to treat this condition.1

This prospective case series investigated the survival and clinical course of 28 cats with FIP administered compounded remdesivir (a prodrug of GS-441524) as monotherapy, with some cats transitioning to compounded oral GS-441524. FIP diagnosis required positive immunocytochemistry or PCR results along with supportive clinical signs. Treatment lasted at least 84 days and 2 weeks past remission.

Initial treatment protocol consisted of remdesivir (10 mg/kg IV every 24 hours for 4 days, followed by 6 mg/kg SC every 24 hours). Cats with ocular or neurologic signs or suboptimal durability of remission received higher dosages. Halfway through the study, GS-441524 tablets were introduced as an alternative for cats experiencing difficulty with injections. Successful treatment markers included resolution of fever, effusions, and clinical signs during the first half of treatment, with normalization of globulin concentration and weight gain in the second half of treatment. Occasional adverse effects consisted of concerns related to injection sites.

Eighty-six percent of all cats survived to 6 months; 6-month survival was 96% excluding cats that died within the first 48 hours. Recurrence of FIP within 6 months was 30% in the low-dose remdesivir group, compared with no recurrence in the high-dose remdesivir and remdesivir and GS-441524 groups. Secondary treatment was needed in 3 cats, and remission was achieved with higher dosages. All 3 cats were maintained on oral GS-441524 and survived to 6 months.

Results of this study indicate injectable remdesivir monotherapy and transition to compounded oral GS-441524 are well tolerated and effective for treatment of FIP. Optimal dosages and durations have not been determined but may exceed 10 to 15 mg/kg every 24 hours for 84 days in some cases. 

… The Takeaways

Key pearls to put into practice:

  • GS-441524 and remdesivir, as well as other drugs (eg, molnupiravir, GC-376), may result in a cure rate of >85% in cats with FIP and appear to be associated with uncommon and generally mild adverse effects. Clinical and clinicopathologic response is often rapid and a predictor of long-term success. 

  • Both oral and injectable forms of medications appear effective for treatment of FIP. Although several potentially effective protocols were described, the ideal dosage, route, combination or concurrent therapies (eg, corticosteroids, antithrombotics), and transition plans are yet to be determined and remain an active area of research.  

  • GS-441524 and remdesivir are effective options for treatment of FIP in locations where they are legally available and accessible, and either drug can likely be used interchangeably. Due to legal ambiguity in many countries, obtaining and using these drugs may not be feasible. The legal and ethical implications of using these therapies until approved options become available should be discussed with the pet owner.