This is a randomized (study drug assigned by chance), open-label (all persons know the study drug assignment) multicenter study to evaluate the effectiveness of telaprevir administered orally as 1125 milligram (mg) twice daily versus 750mg every 8 hours in combination with Peg-IFN-alfa-2a, administered via intramuscular injection once a week, and ribavirin, administered as an oral tablet twice a day, in treatment-naïve study participants with chronic hepatitis C virus (HCV) genotype 1 infection.
Telaprevir will be given orally (by mouth) from Day 1 through Week 12 as 3 tablets (1125mg) twice daily or 2 tablets (750mg) every 8 hours. Peg-IFN-alfa-2a will be administered once a week as an injection under the skin (180 microgram/week) from Day 1 through Week 24 or 48 (based on the patient's treatment response on week 4). Ribavirin is administered orally (by mouth) twice daily from Day 1 through Week 24 or 48 (based on the participant's treatment response on week 4) as 1,000-1,200 mg per day. After the end of treatment (Week 24, Week 48, or at early discontinuation of all study drugs), participants with undetectable HCV RNA at end of treatment will be required to attend follow-up visits until Week 72 safety/tolerability assessments will be performed throughout the treatment period and during the follow-up period.