AIM: To investigate the reduction in hepatitis B virus(HBV) covalently closed-circular DNA(ccc DNA) with entecavir(ETV) or lamivudine(LAM). METHODS: This analysis included patients who had participated in the randomized Phase Ⅲ study ETV-022 comparing ETV vs LAM in nucleos(t)ide-naive, HBe Agpositive patients. Patients received ETV(0.5 mg daily) or LAM(100 mg daily) for a minimum of 52 wk. Patients were eligible to participate in this sub-study if they had paired biopsies at baseline and week 48 with evaluable measurements for hepatic HBV ccc DNA and total hepatic HBV DNA. The main objective was to compare changes in hepatic HBV ccc DNA and total hepatic HBV DNA at week 48 of ETV or LAM treatment, which was a secondary endpoint of study ETV-022. Additional post hoc analyses included linear regression analyses to assess associations of baseline levels and on-treatment changes of ccc DNA with other baseline factors [sex,age, serum HBV DNA, alanine aminotransferase(ALT), Knodell necroinflammatory score, Ishak fibrosis score, total hepatic HBV DNA, and HBV genotype], or ontreatment factors(changes from baseline at week 48 in serum HBV DNA, ALT, Knodell necroinflammatory score, Ishak fibrosis score, total hepatic HBV DNA, and HBe Ag loss at week 48).RESULTS: Overall, 305 patients(ETV = 159; LAM = 146) of ETV-022 had paired baseline and week 48 liver biopsies with evaluable measurements for hepatic HBV ccc DNA and total hepatic HBV DNA, and were included in this analysis. Baseline demographics and disease characteristics were comparable between the two arms. After 48 wk, ETV resulted in significantly greater reductions in hepatic HBV ccc DNA [-0.9 log10 copies/human genome equivalent(HGEq) vs-0.7 log10 copies/HGEq; P = 0.0033] and total hepatic DNA levels(-2.1 log10 copies/HGEq vs-1.6 log10 copies/HGEq; P < 0.0001) than LAM. Virologic, biochemical, and histologic response rates at week 48 were also greater with ETV than with LAM. Baseline HBV ccc DNA levels were positively associated with baseline levels of serum HBV DNA and total hepatic HBV DNA, and negatively associated with HBV genotype F. On-treatment changes in HBV ccc DNA levels were negatively associated with baseline levels of serum HBV DNA and baseline ALT, and were positively associated with on-treatment changes in the levels of serum HBV DNA, total hepatic HBV DNA levels, and ALT, change in Knodell necroinflammatory score, and HBe Ag loss.CONCLUSION: Forty-eight weeks of ETV resulted in greater reductions in ccc DNA and total hepatic HBV DNA than LAM, but long-term therapy may be needed for ccc DNA elimination. AIM: To investigate the reduction in hepatitis B virus (HBV) covalently closed-circular DNA (ccc DNA) with entecavir (ETV) or lamivudine (LAM). METHODS: This analysis included patients who participated in the randomized Phase III study ETV- 022 comparing ETV vs LAM in nucleos (t) ide-naive, HBe Agpositive patients. Patients were eligible participate in this sub-study (0.5 mg daily) or LAM (100 mg daily) for a minimum of 52 weeks if they had paired biopsies at baseline and week 48 with evaluable measurements for hepatic HBV ccc DNA and total hepatic HBV DNA. The main objective was to compare changes in hepatic HBV ccc DNA and total hepatic HBV DNA at week 48 of ETV or LAM treatment, which was a secondary endpoint of study ETV-022. Additional post hoc analyzes included linear regression analyzes to assess associations of baseline levels and on-treatment changes of ccc DNA with other baseline factors [sex, age, serum HBV DNA, alanine aminotransferase (ALT ), Knodell necroin flammatory score, Ishak fibrosis score, total hepatic HBV DNA, and HBV genotype], or ontreatment factors (changes from baseline at week 48 in serum HBV DNA, ALT, Knodell necroinflammatory score, Ishak fibrosis score, total hepatic HBV DNA, and HBe Ag loss at week 48) .RESULTS: Overall, 305 patients (ETV = 159; LAM = 146) of ETV-022 had paired baseline and week 48 liver biopsies with evaluable measurements for hepatic HBV ccc DNA and total hepatic HBV DNA, and were included After 48 wk, ETV resulted in significantly greater reductions in hepatic HBV ccc DNA [-0.9 log10 copies / human genome equivalent (HGEq) vs-0.7 log10 copies / HGEq ; P = 0.0033] and total hepatic DNA levels (-2.1 log10 copies / HGEq vs.-1.6 log10 copies / HGEq; P <0.0001) than LAM. Virologic, biochemical, and histologic response rates at week 48 were also greater with ETV than with LAM. Baseline HBV ccc DNA levels were positiv ely associated with baseline levels of serum HBV DNA and total hepatic HBV DNA, and negatively associated with HBV genotype F. On-treatment changes in HBV ccc DNA levels were negatively associated with baseline levels of serum HBV DNA and baseline ALT, and were positively associated with on-treatment changes in the levels of serum HBV DNA, total hepatic HBV DNA levels, and ALT, change in Knodell necroinflammatory score, and HBe Ag loss. CONCLUSION: Forty-eight weeks of ETV resulting in greater reductions in ccc DNA and total hepatic HBV DNA than LAM, but long-term therapy may be needed for ccc DNA elimination.