Twenty-four weeks of interferon α-2b in combination with ribavirin for Japanese hepatitis C patients:: sufficient treatment period for patients with genotype 2 but not for patients with genotype 1

Hepatitis C virus (HCV) RNA titer and HCV genotype are two major determinants of the outcome of interferon (IFN) monotherapy. To clarify the usefulness of combination therapy with IFN and ribavirin in Japanese hepatitis C patients, we treated patients with a relatively high dose of IFN in combination with ribavirin for 24 weeks and examined the effects in relation to the viral parameters. Two hundred and ninety-five patients were enrolled in the study. The patients received either 6 or 10 million units (MU) of interferon alpha-2b every day for 2 weeks and then three times a week for 22 weeks with a daily dose of either 600 or 800 mg of ribavirin. The treatment response and safety of this treatment were examined. The sustained virologic response (SVR) rates were 26.8% in genotype 1 and 76.5% in genotype 2 (P < 0.001), and 36.1% with the 6 MU group and 45.8% with the 10 MU group (P=0.09). Multivariate analysis indicated that SVR was associated with genotype 2, HCV RNA < 500 kilointernational unit/ml (kIU/ml), and HCV RNA undetectability at week 8 of treatment. Our current study showed that a 24-week course of IFN plus ribavirin combination therapy was effective with respect to virologic response in Japanese hepatitis C patients, particularly in patients with HCV genotype 2.