Dasabuvir (ABT-333) is a non-nucleoside inhibitor of the hepatitis C virus (HCV) non-structural protein 5B (NS5B), an RNA-dependent RNA polymerase. Upon administration and intracellular uptake, dasabuvir binds HCV NS5B polymerase, blocking viral RNA synthesis and replication. The HCV NS5B protein is essential for the replication of the HCV RNA genome.

GnRH:0.33 nM

ABT-333 (Dasabuvir) is at least 7,000-fold selective for the inhibition of HCV genotype 1 polymerases over human/mammalian polymerases. ABT-333 (Dasabuvir) 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. 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[1].

The recombinant HCV polymerases used in this study contain the first 570 amino acids of the 591-amino acid native protein sequence, with a six-histidine tag at the N terminus to facilitate purification by affinity chromatography. Briefly, ABT-333 (Dasabuvir) is incubated with 5 to 50 nM polymerase for 15 min at room temperature, follow by the addition of nucleoside triphosphates (NTPs) and [3H]UTP for 3 h at 30°C. After termination of the reaction, the precipitated RNA is captured by filtration through a GF/B filter. The amount of incorporated [3H]UTP is measured by scintillation counting with a Wallac 1450 MicroBeta counter. The percent inhibition is calculated from the initial rates of inhibited reactions relative to that of the uninhibited control reaction. The mean 50% inhibitory concentration (IC50) and the standard error of the mean (SEM) are calculated via nonlinear regression[1].