GS-9451

GS-9451 is a potent macrocyclic HCV NS3 PI that achieved a median maximal change in HCV RNA of 3.6 log10 IU/mL (range, -4.7 log10 to -3.1 log10 IU/mL) following 3-day monotherapy in treatment-naïve patients with HCV genotype 1 infection during phase I. In multiple GT1a and GT1b replicon cell lines, GS-9451 had mean 50% effective concentrations (EC50s) of 13 and 5.4 nM, respectively, with minimal cytotoxicity; similar potency was observed in chimeric replicons encoding the NS3 protease gene of GT1 clinical isolates. GS-9451 was less active in GT2a replicon cells (EC50 = 316 nM). GS-9451 showed good oral bioavailability in all three species tested.