BACKGROUND AND AIMS: To assess the efficacy of switching Japanese chronic hepatitis B patients from lamivudine monotherapy to entecavir 0.5 mg/day.

METHODS: A retrospective analysis was conducted on 134 patients switched to entecavir between September 2006 and February 2008 for 6 months or more. Patients were divided into three groups based on viral load at entecavir switching point (baseline < 2.6, 2.6-5.0 and > 5.0 log(10) copies/mL).

RESULTS: At baseline, detection of lamivudine-resistant virus was highest in patients with higher hepatitis B virus (HBV) DNA (76% vs 23% in > or = 2.6 and < 2.6 log(10) copies/mL, respectively), and in patients with longest previous exposure to lamivudine (52%, 28% and 24% for > 3 years, 1-3 years and < 1 year, respectively). Two years after entecavir switching, HBV DNA suppression to less than 2.6 log(10) copies/mL was achieved in 100% (32/32), 92% (12/13) and 44% (4/9) of patients in the less than 2.6, 2.6-5.0 and more than 5.0 log(10) copies/mL baseline groups, respectively. Alanine aminotransferase (ALT) normalization occurred in 76-96% and 90-100% of patients following 1 and 2 years of entecavir treatment, respectively. One patient (2.6-5.0 log(10) copies/mL) with lamivudine-resistant mutants at baseline developed entecavir resistance at week 48 during follow up.

CONCLUSION: Switching to entecavir 0.5 mg/day achieves or maintains undetectable HBV DNA levels and ALT normalization over 2 years, especially in patients with viral load less than 5.0 log(10) copies/mL.