Efficacy of a 3C-like protease inhibitor in treating various forms of acquired feline infectious peritonitis

This study evaluated the antiviral protease inhibitor GC376 in cats with naturally acquired FIP, targeting the coronavirus 3C-like protease essential for viral replication. Treated cats showed clinical improvement and remission in a meaningful proportion of cases, providing among the first evidence that direct-acting antivirals could alter the course of this historically fatal disease. Some cats relapsed and required retreatment, and a side effect on developing teeth in young cats was noted. It matters because GC376 demonstrated proof of concept for protease inhibition against feline coronavirus, paralleled later antiviral strategies, and helped open the modern era of curative FIP therapy alongside nucleoside analogs such as GS-441524, fundamentally changing prognosis for affected cats.