Analysis of risk factors, clinical data, treatment outcomes for cats with feline infectious peritonitis using GS-441524 (2020–2024)

Abstract Feline infectious peritonitis (FIP) is a lethal, immune-mediated disease caused by feline coronavirus (FCoV). FIP was considered untreatable; however, GS-441524, a nucleoside analog, has become a hopeful antiviral treatment. Despite its effectiveness, survival outcomes depend on several prognostic factors, especially the type of disease and clinical presentation. This research aimed to assess the effectiveness of GS-441524 in a large population of cats with FIP in Iran, examine survival rates, and identify crucial prognostic factors affecting treatment outcomes. Additionally, it evaluates alterations in clinical, laboratory, and imaging outcomes during treatment, proposing a secure treatment protocol for veterinarians utilizing GS-441524 for FIP. This retrospective study analyzed 629 cats diagnosed with or highly suspected of having FIP in Iran between December 2020 and March 2024. Diagnosis was based on clinical signs, laboratory findings, ultrasonographic features, and therapeutic responses. Cats received GS-441524 via subcutaneous injection and/or oral administration for a minimum of 12 weeks. Dosages were adjusted according to the FIP form, and clinical, laboratory, and imaging data were collected before, during, and at the end of treatment with GS-441524. Dosages were further adjusted based on FIP form, weight gain, clinical improvement, and laboratory or imaging results. Statistical analyses comprised ANOVA, t-tests, chi-square tests, and non-parametric techniques to pinpoint important prognostic indicators and treatment effects. The survival rate reached 94.12%, with a relapse rate of 0.63%. Most reported type was Effusive forms accounted for 54.84% of the cats. Key prognostic factors associated with reduced survival included being male, over 6 years old, having neurological or mixed forms of FIP, and exhibiting fever, icterus, anemia, and thrombocytopenia ( p < 0.05). Significant improvements were observed in parameters such as the A: G ratio, albumin, globulin, bilirubin levels, and changing in imaging findings. The study also assessed dosage modifications during treatment. The average starting dose for effusive forms was 6.9 mg/kg, later increasing to 10.11 mg/kg, while neurological and mixed forms initially required 9.65 mg/kg, which was then raised to 12.7 mg/kg. Treatment duration extended beyond 84 days for 17.32% of cats (109 cats) due to showing abnormalities. Imaging studies confirmed a gradual resolution of abdominal and pleural effusions, reduced lymph node size (both abdominal and mediastinal), decreased kidney size in cats of renomegaly, and regression of gallbladder edema. This research features the largest group of FIP-treated cats in Iran and ranks among the largest worldwide, showcasing impressive survival rates with GS-441524 treatment. Positive results rely on timely intervention, suitable dosage modifications, and extended treatment periods, particularly for cats showing neurological and ocular signs. Major risk factors affecting lower survival rates were fever, icterus, anemia, and low platelet count. These findings provide vital clinical insights for veterinarians, underscoring the need for customized treatment approaches and continued research to enhance FIP outcomes therapy and long-term care.