GC-376 is primarily used as an antiviral agent, particularly effective against coronaviruses. It functions by inhibiting the main protease (Mpro or 3CLpro), an enzyme essential for viral replication. This makes GC-376 a promising candidate for the treatment of diseases caused by coronaviruses, including feline infectious peritonitis (FIP) in cats, where it has shown high efficacy in clinical settings. It has also been investigated for potential use against human coronaviruses such as SARS-CoV-2, the virus responsible for COVID-19. Due to its broad-spectrum activity, GC-376 is considered a valuable lead compound in the development of antiviral drugs targeting RNA viruses. Its application extends to research settings where it serves as a tool compound to study protease inhibition and viral life cycles.