Efficacy and safety of entecavir in lamivudine-refractory patients with chronic hepatitis B: Randomized controlled trial in Japanese patients

Background and Aim: Entecavir is a potent inhibitor of both wild-type and lamivudine-resistant hepatitis B virus (HBV) with proven clinical efficacy. We conducted a randomized, double-blind, multicenter study in Japan (ETV-052) evaluating the efficacy and safety of two doses of entecavir in adult patients with lamivudine-refractory chronic hepatitis B infection. Methods: Eighty-four patients with chronic hepatitis B who were refractory to lamivudine therapy were switched from lamivudine to daily oral doses of 0.5 mg entecavir (41 patients) or 1 mg entecavir (43 patients) for 52 weeks. Results: The proportions of patients achieving the primary end-point (≥2 log₁₀ reduction in HBV-DNA from baseline by polymerase chain reaction assay or undetectable HBV-DNA levels [<400 copies/mL] at week 48) were 90% and 93% for entecavir 0.5 mg and 1 mg, respectively, with 33% of patients in each dosing group achieving <400 copies/mL. The mean reduction in HBV-DNA from baseline was 3.58 and 3.75 log₁₀ copies/mL for entecavir 0.5 mg and 1 mg, respectively. High proportions of patients achieved alanine aminotransferase normalization at week 48 (0.5 mg 86%, 1 mg 78%). Histological improvement was observed in most patients (0.5 mg 52%, 1 mg 60%). Virological breakthrough (increase in HBV-DNA of ≥1 log₁₀ copies/mL from nadir) was observed in one patient but was not associated with selection of entecavir-associated resistance substitutions. Entecavir was well tolerated, with no patients discontinuing study drug due to adverse events. Conclusions: These findings indicate that entecavir is safe and effective for the treatment of Japanese adults with lamivudine-refractory chronic hepatitis B.