Background: We aimed to assess differences in early viral dynamics following treatment with either peg-IFNalpha2a or peg-IFNalpha2b in combination with ribavirin in patients with chronic genotype 1b HCV infection.
Material/Methods: Sixty-one patients in the peg-IFNalpha2a + ribavirin treatment (group alpha2a) and 88 patients in the peg-IFNalpha2b + ribavirin treatment (group alpha2b) were retrospectively analyzed. The early dynamics of HCV RNA over 12 weeks were evaluated. Sustained virological response (SVR) was defined as undetectable HCV RNA at week 24 after end of therapy. First- (day 0–1) and second-phase (day 1–28) viral decline rates were calculated in accordance with theoretical formulae.
Results: Baseline HCV RNA concentrations were almost similar between the 2 groups. In group alpha2a, viral decline was significantly greater than in group alpha2b at weeks 4, 8, and 12. In group alpha2a, viral decline was significantly greater in SVR patients than in non-SVR patients at week 2, whereas significantly greater viral decline in SVR patients was found during weeks 1–12 in group alpha2b. The first-phase viral decline rate was significantly larger in group alpha2a than in group alpha2b (1.31±0.84 vs. 0.70±0.97 log IU/mL/day; p<0.0001). Within SVR patients, first-phase viral decline rate was significantly larger in group α2a compared with group alpha2b (1.45±0.85 vs. 0.78±1.0 log IU/mL/day; p<0.0001). Second-phase viral decline rate was comparable between the groups.
Conclusions: Peg-IFNalpha2a showed earlier viral decline than peg-IFNalpha2b and the difference was obvious, especially in the first-phase viral decline.

Keywords: Models, Biological, Polyethylene Glycols - therapeutic use, Kinetics, Interferon-alpha - therapeutic use, Hepatitis C, Chronic - virology, Hepacivirus - physiology, Genotype, Drug Therapy, Combination, Antiviral Agents - therapeutic use, RNA, Viral - blood, Recombinant Proteins - therapeutic use, ribavirin, Viremia - virology