ABSTRACT
Introduction: Prognosis of cats with feline infectious peritonitis (FIP), hitherto an invariably fatal disease, has purportedly improved with the introduction of the unlicensed nucleoside analog GS-441524 (GS). Method(s): A prospective observational study. Inclusion criteria comprised a complete medical record, characteristic clinical signs and laboratory changes, and a confirmatory RT-PCR test for the presence of feline coronavirus and FIP pathogenic strains in pleural/peritoneal/cerebrospinal fluid samples. Clinical signs, laboratory parameters, and adverse effects were recorded at diagnosis, during treatment, and at the end of a 12-week observation period. Remission was defined as completion of 12 weeks or more of treatment and resolution of clinical signs. Result(s): Overall, 175 medical files were reviewed but only 38 cases met the inclusion criteria. Samples of used vials were analyzed by high-performance liquid chromatography and identified GS-441524 as the active component. Twenty-one cats (55%) were considered in full remission, 7 (18 %) cats are currently treated, and 4 cats are in the 12-week observation period. Two cats experienced a relapse, 1 and 6 weeks after completion of treatment. Six (15%) cats died. Anemia (65%), jaundice (50%), thrombocytopenia (50%), and an albumin globulin ratio under 0.6 (81%) were common findings. Clinical manifestation included effusive (n = 30), noneffusive (n = 3), and neurological (n = 6) forms. Adverse effects included injection site reactions (52% of cats) and pain (95% of cats), and temporary creatinine increase (64%). Conclusion(s): Short-term efficacy against FIP disease, using an unlicensed nucleotide analog, was observed herein. The unknown purity or biological activity of these unlicensed compounds is a major limitation of this treatment.