Pegylated interferon alpha‐2b (Peg‐IFN α‐2b) affects early virologic response dose‐dependently in patients with chronic hepatitis C genotype 1 during treatment with Peg‐IFN α‐2b plus ribavirin

Summary.  Chronic hepatitis C (CH‐C) genotype 1 patients who achieved early virologic response have a high probability of sustained virologic response (SVR) following pegylated interferon (Peg‐IFN) plus ribavirin therapy. This study was conducted to evaluate how reducing drug doses affects complete early virologic response (c‐EVR) defined as hepatitis C virus (HCV) RNA negativity at week 12. Nine hundred eighty‐four patients with CH‐C genotype 1 were enrolled. Drug doses were evaluated independently on a body weight base from doses actually taken. From multivariate analysis, the mean dose of Peg‐IFN α‐2b during the first 12 weeks was the independent factor for c‐EVR (P = 0.02), not ribavirin. The c‐EVR rate was 55% in patients receiving ≥1.2 μg/kg/week of Peg‐IFN, and declined to 38% at 0.9–1.2 μg/kg/week, and 22% in patients given <0.9 μg/kg/week (P < 0.0001). Even with stratified analysis according to ribavirin dose, the dose‐dependent effect of Peg‐IFN on c‐EVR was observed, and similar c‐EVR rates were obtained if the dose categories of Peg‐IFN were the same. Furthermore, the mean dose of Peg‐IFN during the first 12 weeks affected HCV RNA negativity at week 24 (P < 0.0001) and SVR (P < 0.0001) in a dose‐dependent manner. Our results suggest that Peg‐IFN was dose‐dependently correlated with c‐EVR, independently of ribavirin dose. Thus, maintaining the Peg‐IFN dose as high as possible during the first 12 weeks can yield HCV RNA negativity and higher c‐EVR rates, leading to better SVR rates in patients with CH‐C genotype 1.