Reagan KL, Brostoff T, Pires J, Rose A, Castillo D, Murphy BG. Open label clinical trial of orally administered molnupiravir as a first-line treatment for naturally occurring effusive feline infectious peritonitis. J Vet Intern Med. 2024 Nov-Dec; 38(6):3087-3094. doi: 10.1111/jvim.17187. An EveryCat-funded Study
As the world’s only non-profit solely focused on funding feline health research, EveryCat Health Foundation has supported over 70 studies pertaining to the diagnosis and treatment of Feline Infectious Peritonitis (FIP). Several antiviral medications have shown efficacy in treatment, but optimum protocols are still being developed. Molnupiravir, originally developed for the treatment of COVID-19, is an oral antiviral prodrug that has shown promise in successful resolution of FIP in prior studies.
This EveryCat Health Foundation funded study compared the use of Molnupiravir (MPV) with historical controls from previous clinical trials receiving another antiviral drug GS-441524 for effusive FIP. Study design and enrollment criteria were identical in all cases.
A single center and single non-blinded treatment arm trial was conducted with inclusion criteria that included:
– Ultrasonographic evidence of pleural, peritoneal, or pericardial effusion
– Either immunohistochemical or immunocytochemical diagnosis of FIP by a veterinary pathologist or positive FCoV RNA via RT-PCR analysis
– Negative for FeLV/FIV
– No prior antiviral treatment for FIP
– Critically-ill patients that were not expected to survive 48 hours were excluded
– Patients with owners who could not reliably medicate were also excluded
Study Protocol included:
– Patients were treated with oral MPV 10-15 mg/kg twice daily for 84 days
– Patients were examined at weeks 0, 6, and 16 and CBC and chemistry panels were conducted at each of these visits-*
– Owners weighed patients between visits at home with a baby scale
– An FCoV antibody indirect immunofluorescence serology assay was performed at weeks 0 and 16
– Point-of-care ultrasound was used to evaluate effusion volume/depth at each visit
Disease remission was determined at 16 weeks and was defined as:
– Resolution of clinical signs from initial presentation
– Lack of relapse of signs after cessation of drug administration
– Effusion resolution
– Serum globulin and bilirubin normalization
Ten cats (9 DSH or DMH and 1 Burmese) met the inclusion protocol and had a positive FCoV RT-PCR from effusion analysis. Eight cats had peritoneal effusion and two cats had pleural effusion. Two of the ten cats did not survive the study period, but both of these cats died or were euthanized within 24 hours of treatment initiation. The remainder were assessed to be in remission at 16 weeks and remained alive between 7 and 11 months after study period.
No adverse events or biochemical or hematologic adverse events were noted during study period. Drug discontinuation in any patient was not needed during the duration of the study. Effusion resolved in 7/8 cats by week 6 evaluation, and all cats gained weight during the 16-week period.
Compared to GS-441524, MPV met non-inferiority criteria for the primary endpoint of survival and clinical sign resolution at 16 weeks. Survival rates were also similar to what has been noted in prior MPV trials. Limitations of this study include comparing a historical control group rather than a blinded prospective study, a low number of enrolled patients, and the utilization of a compounded drug. As FIP is ultimately a fatal disease without treatment, this clinical trial demonstrated the efficacy of MPV for the successful treatment of effusive FIP without any observed adverse effects.
For Further Reading:
Pedersen NC, Perron M, Bannasch M, Montgomery E, Murakami E, Liepnieks M, Liu H. Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis. J Feline Med Surg. 2019 Apr;21(4):271-281. doi: 10.1177/1098612X19825701.
Roy, M., Jacque, N., Novicoff, W., Li, E., Negash, R., & Evans, S. J. M. (2022). Unlicensed Molnupiravir is an Effective Rescue Treatment Following Failure of Unlicensed GS-441524-like Therapy for Cats with Suspected Feline Infectious Peritonitis. Pathogens, 11(10), 1209. doi.org/10.3390/pathogens11101209