This is a randomized, open-labelled, prospective 96-week study comparing the antiviral efficacy and safety of switching to entecavir 1 mg QD from lamivudine versus maintaining lamivudine 100 mg QD treatment in HBV-infected subjects currently receiving lamivudine monotherapy.

Entecavir has a higher potent antiviral efficacy and a lower drug resistance rate than Lamivudine in nucleoside-naïve CHB patients. The prompt switch from Lamivudine to Entecavir in patients who have insufficient hepatitis B virus suppression (HBV DNA ≥ 60 IU/mL by PCR) may lead to full viral suppression to undetectable level by PCR method. The prompt switch from Lamivudine to Entecavir in patients who have insufficient hepatitis B virus suppression (HBV DNA ≥ 60 IU/mL) may preclude development of drug resistance. The results of this study will provide a rationale for switch treatment from one antiviral to another one, especially from LAM to ETV.

Inclusion Criteria:

• Adult subjects (18-70 years of age) currently taking lamivudine monotherapy for chronic HBV infection for at least 6 months with ≥ HBV DNA 60 IU/mL level and HBeAg positive at baseline.

Exclusion Criteria:

• All subjects will be tested for presence of M204V/I mutations in the YMDD motif at baseline. Subjects with M204V/I mutations in the YMDD motif at baseline are not eligible for the study.
• Subjects treated with other antiviral drugs (e.g. adefovir) in combination with lamivudine are not eligible for this study.
• Subjects should have ALT < 10 x ULN, and no evidence of hepatocellular carcinoma.
• Subjects should be without serological evidence of co-infection with HCV, HIV, or HDV.
• Subjects with decompensated liver disease, as well as pregnant or breast-feeding women, will not be eligible for the study.