The purpose of this study is to collect information on the efficacy, safety and tolerability of telaprevir (in combination with other medications), in patients who have a history of intravenous drug use with genotype 1 chronic hepatitis C, under substitution therapy (eg., methadone, buprenorphine) and/or followed in addiction centres.

This is a multicenter, non-interventional, observational, prospective study to evaluate the efficacy, safety, and adherence to telaprevir in ex-People Who Inject Drugs (ex-PWIDs) infected with genotype 1 chronic hepatitis C and any fibrosis stage including compensated cirrhosis, who are receiving substitution therapy (eg, methadone, buprenorphine) and/or are being followed in an addiction center. Patients may be treatment naïve or relapsers. Participating physicians are to offer enrollment in this study to all eligible patients at their site in who they plan to initiate triple therapy with telaprevir, pegylated interferon alfa (PegIFN alfa), and ribavirin (RBV). A target of 115 patients will participate in this study. The duration of each patient's participation in this study will be up to approximately 60 weeks. After obtaining the signed participation agreement or ICF, selection criteria will be reviewed to verify the patient's eligibility. Data will be recorded in the electronic case report form (CRF) at 6 time points for each patient which correspond to routine care visits: inclusion, and at the patient's routine care visit closest to Week 4, 12, and 24, end of treatment, and end-of-follow-up (e.g., approximately 12 weeks after end-of-treatment). No additional blood, urine, or other biological samples will be required, and no additional investigations, beyond the routine clinical management of the patient, will be performed.

Inclusion Criteria:

Have HCV genotype 1, a quantifiable serum HCV RNA, recent (within 18 months of baseline) documentation of the degree of liver fibrosis (Metavir F0-F4; Ishak 0-6) assessed by liver biopsy or non-invasive test (eg, fibrotest, fibroscan); Physician decision to start triple therapy with telaprevir and PegIFN alfa/RBV; Have never been treated with antiviral treatment (naïve) or who have relapsed after IFN or PegIFN plus RBV (relapsers); History of injecting drugs and are currently under stable substitution therapy (eg, methadone, buprenorphine) and/or followed in an addiction center.

Exclusion Criteria:

Infected or coinfected with HCV of a genotype other than genotype 1; Previous or current treatment with a DAA therapy; Have any contraindication specified in the SmPC for telaprevir, PegIFN alfa, or RBV; Have a history or other evidence of decompensated liver disease, or have coinfection with active hepatitis B or HIV; Currently participating in another investigational study or clinical study.

Men or women who have HCV infection genotype 1, a quantifiable serum HCV RNA, documentation of the degree of liver fibrosis assessed by liver biopsy or non-invasive test (eg, fibrotest, fibroscan), physician decision to start triple therapy with telaprevir and PegIFN alfa/RBV, have never been treated with antiviral treatment (naïve) or who have relapsed after IFN or PegIFN plus RBV (relapsers), have a history of injecting drugs, and are currently under stable substitution therapy (eg, methadone, buprenorphine) and/or followed in an addiction center will be eligible to enter this study.