Dasabuvir (ABT-333) is at least 7,000-fold selective for the inhibition of HCV genotype 1 polymerases over human/mammalian polymerases. Dasabuvir (ABT-333) inhibits the polymerase enzymatic activity of genotype 1 laboratory strain enzymes (H77, BK, N, and Con1 strains), as well as enzymes produced from polymerase genes from HCV genotype 1-infected subjects, with IC50s between 2.2 and 10.7 nM. Dasabuvir (ABT-333) inhibits replication of HCV subgenomic replicons in cell culture assays, with EC50 values of 7.7 and 1.8 nM against genotype 1a (H77) and 1b (Con1), respectively. In the presence of 40% human plasma, there is a 12- to 13-fold decrease in inhibitory potency, yielding EC50s of 99 and 21 nM for HCV genotype 1a (H77) and 1b (Con1) replicons, respectively.