A phase 1, randomized, placebo-controlled, 3-day, dose-ranging study of GS-5885, an NS5A inhibitor, in patients with genotype 1 hepatitis C

Background & Aims: GS-5885 is an inhibitor of the hepatitis C virus (HCV) NS5A protein and exhibits potent suppression of genotype 1 HCV replicons. The safety, tolerability, pharmacokinetics, antiviral activity, and resistance profile of once-daily GS-5885 doses of 1-90 mg were evaluated in patients with chronic genotype 1 HCV. Methods: Genotype 1 HCV-infected patients were randomized to 3 days of once-daily (QD) dosing with placebo (n = 12) or GS-5885 1 mg (n = 10), 3 mg (n = 10), 10 mg (n = 20), 30 mg (n = 10), or 90 mg (n = 10). Plasma samples for pharmacokinetics, HCV RNA, and NS5A sequencing were collected through day 14. Results: GS-5885 was well tolerated and resulted in median maximal reductions in HCV RNA ranging from 2.3 log(10) IU/ml (1 mg QD) to 3.3 log(10) IU/ml (10 mg QD in genotype 1b and 30 mg QD). E-max modeling indicated GS-5885 30 mg was associated with >95% of maximal antiviral response to HCV genotype 1a. HCV RNA reductions were generally more sustained among patients with genotype 1b vs. 1a. Three of 60 patients had a reduced response and harbored NS5A-resistant virus at baseline. NS5A sequencing identified residues 30 and 31 in genotype 1a, and 93 in genotype 1b as the predominant sites of mutation following GS-5885 dosing. Plasma pharmacokinetics was consistent with QD dosing. Conclusions: During 3 days of monotherapy, low doses of GS-5885 demonstrated significant antiviral activity in genotype 1a and 1b HCV-infected patients. GS-5885 is currently being evaluated in combination with direct antiviral regimens with and without peginterferon. (C) 2012 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.