Background and aimsAddition of a 40kD polyethylene glycol moiety to interferon-α-2a [peginterferon-α-2a (40kD)] improves pharmacokinetic properties over those of standard interferon. We conducted a phase II study to assess the safety and initial efficacy of peginterferon-α-2a (40kD) plus ribavirin combination therapy in patients with chronic hepatitis C (CHC).MethodsTwenty patients received open-label 180μg peginterferon-α-2a (40kD) subcutaneously once weekly and oral ribavirin 1000 or 1200mg daily for patients weighing <75 or ≥75kg, respectively, for a period of 24 weeks. Patients with hepatitis C virus (HCV) genotype 1 and a virological response at week 24 received study drugs for an additional 24 weeks.ResultsA sustained virological response, defined as undetectable HCV RNA 24 (i.e. <100 copies/ml) weeks after completing the therapy, was achieved in 50% of patients in an intent-to-treat analysis (6/16 genotype 1 and 4/4 genotype non-1). Adverse events were similar to those reported with unmodified interferon plus ribavirin combination therapy. Anaemia led to ribavirin dose reduction in five patients. Neutropenia led to dose reduction in three patients treated with peginterferon-α-2a (40kD).ConclusionsThe addition of ribavirin to a once-weekly peginterferon-α-2a (40kD) regimen should be investigated in larger clinical trials.