Abstract: Background – Untreated FIP is generally considered fatal in cats. The best-studied antiviral drug, GS-441524, is unlikely to reach the clinical market in the USA; the related compound remdesivir has limited published data on use for treating FIP. Hypothesis/Objectives – This is a clinical trial comparing overall survival between oral remdesivir and GS-441524 to treat noneffusive FIP. We hypothesize that the rate of remission and relapse will be similar between the two treatment arms. Animals - Twenty client-owned cats with confirmed spontaneous noneffusive FIP with no concurrent or previous anticoronaviral administration. Methods – This is a double-blind, prospective, randomized clinical trial with two treatment arms. 10 cats per arm received either GS-441524 (15-20 mg/kg) or remdesivir (30-40 mg/kg) PO once daily for 12 weeks. Physical examination, CBC, and chemistry were performed at 0, 6, and 16 weeks. Results – Eight of ten cats in the GS-441524 and nine of ten cats in the remdesivir arm survived to 16 weeks (p=0.5). Two cats in the GS-441524 group experienced relapse at 16 weeks; relapse was not observed in the remdesivir group. The most common adverse events were GI signs, which were observed in 6 cats treated with remdesivir and 3 cats treated with GS-441524 (p=0.4). Conclusions and clinical importance – This study represents the first direct comparison of oral remdesivir and GS-441524 to treat noneffusive FIP. No statistical difference in survival or adverse drug reactions was observed, laying a foundation to expand clinical options in the treatment of this otherwise fatal disease.
