Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced interim results from a Phase II, multi-center, randomized, dose-ranging study (n=332) assessing the safety and antiviral activity of MK-5172, an investigational, once-daily, oral NS3/4A protease inhibitor for the treatment of chronic hepatitis C virus (HCV) genotype 1 infection in combination therapy in treatment-naïve patients. These data will be presented this week at the American Association for the Study of Liver Diseases Annual Meeting (AASLD). The primary efficacy endpoint of the study was to evaluate the complete early viral response (cEVR) of four regimens of MK-5172 in combination with peginterferon alfa-2b and ribavirin (PR) compared to the control arm in which patients received a 4-week lead-in of PR followed by the addition of VICTRELIS ® (boceprevir) 200 mg Capsules. cEVR was assessed by the proportion of patients who achieved undetectable virus (HCV RNA) at treatment week (TW) 12 in the investigational arms and at TW 16 in the control arm. The MK-5172 regimens had rates of cEVR ranging from 82.8 to 93 percent, versus the control of 74.2 percent. In the initial cohort, termed the "Vanguard Cohort," (n=136), 96 percent of patients (25/26) who received a regimen containing 100 mg QD of MK-5172 with PR achieved sustained virologic response (SVR) 12, defined as having undetectable virus (HCV RNA) 12 weeks after treatment ended, compared to 54 percent of patients (13/24) in the control arm. “We are excited by these interim results evaluating MK-5172 in combination therapy,” said Eliav Barr, M.D., vice president, Infectious Diseases, Project Leadership and Management, Merck Research Laboratories. “Our commitment to chronic hepatitis C remains steadfast. We look forward to continuing our studies of MK-5172, including in interferon-free regimens." Currently planned studies evaluating interferon-free regimens with MK-5172 will be dosed at 100 mg QD.