15, 23.36, 17.77, and 14.76 μM · h for doses of 300 mg BID, 600 mg BID, 600 mg QD, and 800 mg QD, respectively. With BID dosing, there was some accumulation, with a geometric High Content Screening mean accumulation ratio of 1.2-1.8 for AUC0-12h and Cmax. Both AUC0-12h and Cmax appeared to increase greater than dose proportionally between 300- and 600-mg BID doses. The intersubject variability for AUC, Cmax, and Ctrough was high (i.e., greater than 30% coefficient of variation) for each dosing regimen. With QD administration, there was extensive overlap in individual AUC0-24h, Cmax, and C24h values between 600- and 800-mg QD doses because of the high variability. Steady-state Ctrough concentrations on day 28 after

QD doses (25 μM for 600 mg QD and 30 μM for 800 mg QD) were similar and generally lower than the BID doses (65 μM for 300 mg BID and 100 μM for 600 mg BID). Trough concentrations after morning and evening doses for Protease Inhibitor Library both BID dosing regimens were generally similar. Figure 2 illustrates change in the mean log10 HCV RNA at day 1 through day 42, which includes 28 days of triple therapy followed by 14 days of Peg-IFN-α-2a and RBV alone. In all dose groups, vaniprevir was associated with a rapid two-phase decline in HCV RNA, compared to the more gradual decrease in viral load observed in patients receiving placebo. HCV RNA levels were approximately 3log10 IU/mL lower in vaniprevir-treated patients, compared to placebo recipients, during the vaniprevir dosing period.

Rates of MCE RVR were significantly higher in each of the vaniprevir dose groups, compared to the control regimen, satisfying the primary hypothesis that at least one vaniprevir dose group would result in higher RVR rates than placebo (Table 2; PP analysis, N = 88). The full analysis set population (N = 94) showed nearly identical results (Supporting Table 1). Rates of RVR also appeared dose related among vaniprevir recipients, with numerically higher responses in patients receiving 600 mg BID and 800

mg QD compared with those receiving 300 mg BID and 600 mg QD (78.9% and 83.3% versus 75.0% and 68.8%); however, the study was not powered to perform formal statistical comparisons between vaniprevir dose groups. All vaniprevir treatment regimens also had numerically higher EVR and SVR rates, compared to the control regimen (P = not significant; Table 3). However, the difference in rates of SVR between vaniprevir and placebo treatment groups did not achieve statistical significance, which was expected given the relatively small sample size and the focus of the study design on the RVR endpoint. Baseline population resistance sequence data were available for 84 of the 94 patients in the study. One genotype 1b–infected patient (AN 3300) exhibited the D168E variant at baseline (Table 4). This patient showed a slow decline in HCV RNA throughout the 28-day vaniprevir dosing period (classified as a “slow responder”), although this patient did not meet the protocol-defined failure criteria (Fig. 3).