Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis

This pivotal field trial treated cats with naturally occurring feline infectious peritonitis (FIP), long considered almost uniformly fatal, using the nucleoside analog GS-441524, a parent compound related to remdesivir. Cats received subcutaneous injections over an extended course, and a substantial majority achieved sustained remission, with reversal of clinical signs and prolonged survival. The study transformed FIP from a death sentence into a treatable disease and catalyzed a global movement of owners and clinicians seeking access to the drug. It matters because it provided the first rigorous evidence that direct-acting antiviral therapy could cure a feline coronavirus disease, reshaping clinical expectations and foreshadowing the broader relevance of nucleoside-analog antivirals against coronaviruses.