Rationale and design of the REPEAT study: a phase III, randomized, clinical trial of peginterferon alfa-2a (40 kDa) plus ribavirin in non-responders to peginterferon alfa-2b (12 kDa) plus ribavirin.

OBJECTIVE: The REtreatment with PEgasys in pATients not responding to prior peginterferon alfa-2b (12 kDa)/ribavirin combination therapy (REPEAT) study is a phase III, randomized, parallel group, multinational clinical trial. The main objective is to compare the efficacy and safety of 48 and 72 weeks of treatment with peginterferon alfa-2a (40 kDa) (PEGASYS) plus ribavirin (COPEGUS) in patients who did not respond to previous peginterferon alfa-2b (12 kDa) plus ribavirin therapy. STUDY DESIGN: Patients will be randomized to one of four treatment groups: two groups will receive peginterferon alfa-2a (40 kDa) at the standard dose of 180 mug once weekly for 48 or 72 weeks. The other two groups will receive a 12-week high-dose induction regimen with peginterferon alfa-2a (40 kDa) 360 mug once-weekly followed by 60 or 36 weeks of peginterferon alfa-2a (40 kDa) 180 mug once weekly. All patients will receive the standard dose of ribavirin (1000 or 1200 mg/day) throughout treatment. The primary efficacy variable is the rate of sustained virological response, defined as non-detectable hepatitis C virus (HCV) RNA (<50 IU/ml) 24 weeks after the end of treatment. Secondary variables include the percentage of patients with non-detectable HCV RNA at the end of treatment, the percentage of patients with at least a 2-log10 decrease in serum HCV RNA at weeks 12 and 24 of treatment, and the percentage of patients with non-detectable HCV RNA at treatment weeks 12, 24 and 48. Safety data will be recorded and analysed throughout the entire course of the study with the assistance of a Safety Review Board.