Purpose: A high rate of sustained viral response (SVR) in Koreans with chronic hepatitis C (CHC) is related to a favorable IL28B genotype. We compared two dosing strategies for peginterferon alfa-2a in Koreans with CHC and defined the combined effect of polymorphisms and dosing on the virological response. Methods: A total of 178 treatment-naïve patients with CHC genotype 1 were prospectively enrolled. All patients were randomly assigned to treatment with one of two peginterferon alfa-2a regimens: 180 μg per week for 48 weeks (full-dose group) or 180 μg per week during the first 12 weeks followed by 135 μg per week for the next 36 weeks (dose-reduction group). Polymorphisms related to IL28B, ITPA, C20orf194 and SLC29A1 were studied. Results: SVR rates did not differ between the full-dose and dose-reduction groups (56.5 and 51.2 %, respectively, p = 0.474). The frequency of additional reductions of the peginterferon dose because of adverse events was higher in the full-dose group than in the dose-reduction group. SVR rates in patients homozygous for the IL28B major allele were higher than those in patients for the other IL28B alleles. For patients with unfavorable IL28B genotypes, SVR was less likely to be achieved in the dose-reduction group than in the full-dose group. Conclusions: In Koreans with HCV genotype 1, the virological response to treatment did not differ between a full dose and reduced dose (≥80 % of full dose) of peginterferon alfa-2a. However, in the patients with unfavorable IL28B genotypes, the full-dose treatment of peginterferon alfa-2a may be beneficial.
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