First analytical confirmation of drug-induced crystal nephropathy in felines caused by GS-441524, the active metabolite of Remdesivir.

GS-441524 is an adenosine nucleoside antiviral demonstrating significant efficacy in the treatment of feline infectious peritonitis (FIP), an otherwise fatal illness, resulting from infection with feline coronavirus. However, following the emergence of COVID-19, veterinary development was halted, and Gilead pursued clinical development of a GS-441524 pro-drug, resulting in the approval of Remdesivir under an FDA emergency use authorization. Despite lack of regulatory approval, GS-441524 is available without a prescription through various unlicensed online distributors and is commonly purchased by pet owners for the treatment of FIP.