ALG-097111

ALG-097111 is an investigational **small-molecule antiviral** developed by **Aligos Therapeutics** for **COVID-19**. It is a potent and selective inhibitor of the **SARS-CoV-2 3-chymotrypsin-like cysteine protease**, also known as the **main protease**, a viral enzyme required for coronavirus polyprotein processing and replication. Reported preclinical data indicate nanomolar biochemical potency against the viral protease and strong selectivity over human cathepsin L, supporting a targeted antiviral mechanism with reduced concern for this common host protease off-target. In a Syrian hamster SARS-CoV-2 infection model, subcutaneous ALG-097111 given with ritonavir produced marked reductions in lung viral RNA and infectious virus titers. The compound appears to have remained at the **preclinical or research-stage** level, with no identified marketed brand name and no publicly disclosed chemical structure in the provided material.