The science behind the FIP cure
Dr. Niels Pedersen's studies at UC Davis changed everything in 2019. Here is a summary of the most relevant research that transformed the prognosis of this disease.
Dr. Niels Pedersen: UC Davis, 2019
The first clinical trial to show that GS-441524 could cure FIP in cats with confirmed naturally occurring disease. This study in 31 cats set the basis of modern treatment and the dosing guidance still in use today.
View the study en PubMednaturally occurring FIP
survivors
prognosis changed
Key studies
The published evidence behind antiviral treatment for FIP.
Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis
Clinical study in 31 cats with naturally occurring FIP (severe neurological and ocular forms excluded), treated with subcutaneous GS-441524 for at least 12 weeks. 25 of the 31 became long-term survivors, and the optimum dose turned out to be 4 mg/kg a day. It is the reference study for GS-441524.
Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis
Field trial in 20 cats treated with the protease inhibitor GC376. 19 regained outward health within two weeks, but 13 relapsed and stopped responding; 7 were in remission at the time of writing. It opened the door to antivirals aimed at the FIP virus.
Molnupiravir treatment of 18 cats with feline infectious peritonitis: A case series
A series of 18 cats with FIP treated in Japan with oral molnupiravir, 10-20 mg/kg twice a day for 84 days. 14 completed treatment and were in remission at the time of writing; 4 died or were euthanized in the first week. Three had neurological or ocular signs.
Feline Infectious Peritonitis: European Advisory Board on Cat Diseases Guidelines
The ABCD (European Advisory Board on Cat Diseases) guidelines review FIP: how it arises, how it is diagnosed and how it is treated. They conclude that antivirals now allow many cats to recover from a previously fatal disease, and that nucleoside analogues such as oral GS-441524 are very effective, although they are not available in every country.
Papers and studies to download
Reference documents for vets and owners who want to go deeper into the scientific evidence.
89 FIP cases treated with GS-441524
A retrospective analysis of 89 cats diagnosed and treated with GS-441524 in Spain. It covers dosing, duration, clinical response and post-treatment follow-up.
GS-441524 for treatment of cats with naturally occurring FIP
The UC Davis study (2019) in 31 cats that established the efficacy of GS-441524 and the basis of today's dosing protocols.
A review of feline infectious peritonitis virus infection: 1963-2008
A review of 45 years of research on FIP virus infection, by Dr. Pedersen (UC Davis) in the Journal of Feline Medicine and Surgery.
Molnupiravir treatment of 18 cats with FIP: a case series
A case series published in the Journal of Veterinary Internal Medicine (2023): 18 cats treated with oral molnupiravir, 14 of them in remission at the time of writing. It includes the dose used.
Unlicensed GS-441524-like antiviral therapy can be effective for at-home treatment of FIP
A survey of 393 owners who treated their cat at home with unlicensed GS-441524-like antivirals: progress, relapses and complications as reported by the owners. The authors point out its limits: self-reported data, with no way to confirm what the preparations contained.
Links to external studies point to PubMed or to the original journals. The PDF of the Spanish study by Dr. Vicky Vives is downloaded directly from this site.
The scientific evidence
What the studies consistently show about antiviral treatment for FIP.
Cure rate in treated cats according to the two reference registries: CureFIP (92.7%) and FIPMed (93%).
The minimum treatment length in the Pedersen et al. study (2019): at least 12 weeks.
There are studies with both injectable and oral GS-441524; the ABCD guidelines (2023) note that oral GS-441524 is very effective.
Neurological and ocular forms need higher doses than the rest (FelineVMA guide, 2025).
The European ABCD guidelines (Tasker et al., 2023) state that antivirals now allow many cats to recover from a previously fatal disease.
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