Suboptimal Responders to Adefovir Switching to Entecavir

Inclusion Criteria: * Chronic infection with hepatitis B virus (HBV)(detectable hepatitis B surface antibody (HBsAg) at screening and at least 24 weeks prior to screening, or detectable HBsAg for \<24 weeks and negative for immunoglobulin M core antibody) * Documentation of hepatitis B e antigen (HBeAg) positive or negative status * Naive to nucleoside/nucleotide analogues, with the exception of adefovir * Suboptimal response to adefovir treatment * No lamivudine/telbivudine, entecavir, or adefovir resistance-associated substitutions at screening * Male or female gender, aged 16 years and older * Compensated liver function * Serum alanine aminotransferase level \<10\*upper limit of normal at screening Exclusion Criteria: * Women who are pregnant or breastfeeding * Evidence of decompensated cirrhosis * Coinfection with HIV, hepatitis C virus, or hepatitis D virus * Recent history of pancreatitis (within 24 weeks prior to the first dose of study medication) * Chronic renal insufficiency, defined as a creatinine clearance \<50 mL/min * Current abuse of illegal drugs or alcohol, sufficient in the investigator's opinion to prevent adequate compliance with study therapy or to increase the risk of hepatotoxicity or pancreatitis * Other serious medical conditions that might preclude completion of this study or that require chronic administration of prohibited medications * Serum creatinine level \>1.5 mg/dL; hemoglobin level \<10.0 g/dL; platelet count \<70,000/mm\^3; absolute neutrophil count \<1500 cells/mm\^3; serum alpha fetoprotein level \>100 ng/mL * Except adefovir, any prior therapy with nucleoside or nucleotide analogue antiviral agents with activity against hepatitis B (eg, lamivudine, entecavir), or any other experimental anti-HBV antiviral, or any China Traditional Medicine * Therapy with interferon, thymosin alpha, or other immunostimulators within 24 weeks of randomization * Required chronic administration of medications that cause immunosuppression, that are associated with a high risk of nephrotoxicity or hepatotoxicity, or that affect renal excretion.