• Undetectable HCV RNA [ Time Frame: at end of treatment ] [ Designated as safety issue: No ]
• Undetectable HCV RNA [ Time Frame: 48 weeks after completion of treatment (Groups B, C, and D) ] [ Designated as safety issue: No ]
• Adverse events and clinical laboratory assessments, including ALT and other liver function tests. [ Time Frame: throughout study ] [ Designated as safety issue: Yes ]
• Genotypic and phenotypic analyses of the NS3•4A HCV region. [ Time Frame: throughout study ] [ Designated as safety issue: No ]
• Pharmacokinetic assessments of telaprevir, Peg-IFN-a-2a, and RBV. [ Time Frame: throughout study ] [ Designated as safety issue: No ]

• Undetectable HCV RNA at end of treatment.
• Undetectable HCV RNA 48 weeks after completion of treatment (Groups B, C, and D).
• Adverse events and clinical laboratory assessments, including ALT and other liver function tests.
• Genotypic and phenotypic analyses of the NS3•4A HCV region.
• Pharmacokinetic assessments of telaprevir, Peg-IFN-a-2a, and RBV.

The PROVE3 trial is a partially double blinded, randomized, Phase 2 research study of an investigational drug, Telaprevir (VX-950) or Placebo, with peginterferon alfa-2a (Pegasys®), and ribavirin (Copegus®) in people with genotype 1 hepatitis C who have not achieved a Sustained Viral Response (SVR) with a previous treatment of interferon therapy.

• Drug: Telaprevir
• Drug: Ribavirin
• Drug: Peg-interferon Alfa-2a

• Placebo Comparator: Placebo + Peg-IFN + RBV for 24 weeks followed by Peg-IFN + RBV for 24 weeks
• Experimental: Telaprevir + Peg-IFN + RBV for 24 weeks followed by Peg-IFN + RBV for 24 weeks
• Experimental: Telaprevir + Peg-IFN for 24 weeks
• Experimental: Telaprevir + Peg-IFN + RBV for 12 weeks followed by Placebo + Peg-IFN + RBV for 12 weeks

Inclusion Criteria:

• Males and females between 18 and 70 years old
• Detectable plasma HCV RNA > or = 10,000 IU/mL
• Must have chronic hepatitis C (genotype 1) and have already received at least one prior course of peginterferon with ribavirin
• Can not also be infected with HIV (AIDS) or hepatitis B
• Must be judged to be in general good health and able to receive Pegasys® and Copegus®.
• No drug or alcohol abuse in the last year
• Must agree to use two effective methods of birth control during the study and for 6 months after you stop taking study medication. One of the methods needs to be a 'barrier' method (condom or diaphragm)
• If you are a woman, you can not be in this study if you are pregnant or nursing.

Exclusion Criteria:

• Participation in any clinical trial of a HCV protease inhibitor of any duration.
• Prior response to therapy and failure to achieve SVR which was due to treatment non-compliance
• Any other cause of significant liver disease in addition to hepatitis C; this may include but is not limited to, hepatitis B, drug or alcohol-related cirrhosis, autoimmune hepatitis, hemochromatosis, Wilson's disease, nonalcoholic steatohepatitis, or primary biliary cirrhosis.
• Diagnosed or suspected hepatocellular carcinoma.
• History of or current evidence of decompensated liver disease.
• Participation in any clinical trial of an investigational drug within 90 days before drug administration or participation in more than 2 drug studies in the last 12 months (exclusive of the current study).