Chemical structures of HCV inhibitors used in the study. PSI-6130, β-d-2′-deoxy-2′-fluoro-2′-C-methylcytidine; R7128, PSI-6130 prodrug; RO2433, PSI-6130 uridine metabolite; NM107, 2′-C-methylcytidine; R1479, 4′-azidocytidine; NNI-1, thiophene-2 caboxylic acid.