6 Informed written consent was obtained from all patients. HCV RNA levels

were determined using the Roche Cobas TaqMan HCV Test, v2.0 (lower limit of quantification, 25 IU/mL; lower limit of detection, 10 IU/mL; Roche, Pleasanton, CA) at baseline check details and days 1 (2, 4, 6, 8, 12, 16, and 20 hours post–first dose), 2, 3, 4, 5, 7, 9, 11, 14, 15, 16, 17, 21, and 28. Viral breakthrough was defined as an HCV RNA increase by at least 0.5 log10 after HCV RNA nadir while receiving BMS-790052. Serum specimens were collected for potential genotypic analysis at baseline and days 1 (4, 8, and 12 hours post–first dose), 2, 4, 7, and 14. After amplification of the NS5A coding region, a genotypic analysis was performed by population sequencing to determine the emergence of viral variants after the administration of multiple doses of BMS-790052. The complete study design and resistance analysis methodology have been described elsewhere.5, 6 Genotypic analysis of HCV NS5A complementary Selleckchem Gefitinib DNA was performed at baseline and seven time points (days 1 [4, 8, and 12 hours post–first dose], 2, 4, 7, and 14) for all patients receiving BMS-790052 when HCV RNA levels were >1,000 IU/mL and, in some instances, when HCV RNA levels were <1,000 IU/mL. Variants identified within the N-terminal region of NS5A by population sequencing are shown in Tables 1 and 2. Transient replication assays

were used to assess the contribution of amino acid substitutions to BMS-790052 resistance and to estimate the relative replicative ability (i.e., fitness) of the variants. Many of these substitutions were previously identified during in vitro replicon studies, and others are novel substitutions.4, 5, 11 Values for previously described substitutions (Tables 1 and 2) have been updated

to reflect selleck compound additional test occasions. HCV RNA levels observed during the 14-day monotherapy study are summarized for each dosing cohort in Fig. 1A-F. NS5A variants identified from individual patients treated with BMS-790052 are summarized in Table 3A-F. The percent values shown in the tables are estimates based on population sequencing chromatograms. Based on the results of reconstitution experiments, variants present at ≥20% are readily detectable from the chromatograms (see Materials and Methods). We were also able to estimate variants that were present at less than 20% when they were detected at previously characterized NS5A resistance sites (residues 28, 30, 31, and 93 of genotype 1a and 31 and 93 for genotype 1b). Results from each dosing cohort are reported on below. Figure 1A shows HCV RNA levels, and Table 3A shows resistant substitutions identified in the specimens derived from patients treated with 1 mg of BMS-790052. Known resistant variants were not detected in baseline specimens from any of the patients in this cohort. Patients A and B (genotype 1a) experienced maximal HCV RNA declines of ≥2.0 log10 (Fig. 1A).