Description_x000D_ Biochem/physiol Actions_x000D_ Lomibuvir (VX-222; VCH-222) is a non-cytotoxic, orally active non-nucleoside inhibitor (NNI) against hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase (genotype 1a/1b IC50 = 0.94/1.2 μM). Lomibuvir exhibits HCV genotype-selective antiviral activity in vitro (genotype 1a//1b EC50 = 23.3 nM/12 nM; ineffective against 2a & 2b) and in vivo by targeting HCV NS5B thumb II allosteric pocket, exhibiting no inhibitory potency against human DNA polymerase (α, β, γ IC50 ≥56 μM), respiratory syncytial virus, Influenza A and B, and West Nile virus.