EXPRESS: Renal Health in Cats with Feline Infectious Peritonitis treated with GS-441524: Baseline Findings and Longitudinal Effects.
de Witt Curtius CC, Meli ML, Crespo Bouzon A, Wenk J, Stachowski JM, Cerchiaro I, Pineroli B, Unterer S, Felten S, Major A, Meunier SM, Howard J, Zwicklbauer K, Dorsch R, Hartmann K, Hofmann-Lehmann R, Spiri AMM · Journal of Feline Medicine and Surgery · 12 August 2026
GS-441524 reverses FIP-associated renal abnormalities, but avoid unnecessarily prolonged treatment due to potential renal dysfunction risk.
This prospective longitudinal study evaluated renal health in 80 cats with confirmed feline infectious peritonitis (FIP) treated with oral GS-441524 for 42 days, with follow-up assessments extending to day 183. At baseline, the majority of cats exhibited significant renal abnormalities attributable to FIP itself: 91.3% had proteinuria (UPC >0.2), 83.8% had elevated urinary cystatin B (uCysB), and most had markedly elevated inflammatory markers (AGP and SAA). Urine protein electrophoresis revealed predominantly tubular and mixed proteinuria patterns at baseline, suggesting FIP-associated renal tubular injury. During and following GS-441524 treatment, substantial improvements were observed across most renal parameters: proteinuria resolved in the majority of cats (only 3.8% had UPC >0.2 by D183), uCysB declined significantly, and inflammatory markers normalized. However, serum creatinine concentrations increased over time, with 23.8% of cats exceeding 140 µmol/L by D183 compared to 2.5% at baseline. Potential renal dysfunction criteria (creatinine >140 µmol/L or SDMA ≥18 µg/dL combined with USG <1.035) were met in 8.8% of cats by D183. Urinary FCoV RNA was detected more frequently than blood viral RNA at baseline (68.8% vs. 61.3%), reversing by day 7. The authors concluded that GS-441524 treatment effectively reversed FIP-associated renal inflammation and proteinuria, though a small subset of cats developed findings consistent with potential renal dysfunction. Whether this represents delayed FIP-related injury or antiviral drug toxicity remains unclear, supporting the recommendation to avoid unnecessarily prolonged treatment courses.
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