An inhibitor of 3C- and 3C-like proteases; inhibits recombinant poliovirus, FMDV, and HRV 3C proteases (IC50s = 1.77, 1.16, and 0.2 µM, respectively); inhibits recombinant Norwalk virus, MD145 virus, TGEV, and SARS-CoV 3C-like proteases (IC50s = 0.49, 0.96, 0.82 and 4.35 µM, respectively); inhibits the cytopathic effect of SARS-CoV-2 in infected Vero E6 cells (EC50 = 3.37 µM); reduces liver viral titers by 9.86- and 21.99-fold in a model of MHV A59 infection at doses of 50 and 100 mg/kg per day, respectively