Background & Aims: We examined the durability of the virological response after discontinuing lamivudine (LVD) in chronic hepatitis B (CHB) patients with LVD-resistant hepatitis B virus (HBV), who responded to LVD plus adefovir (ADV) combination therapy, and the outcome of switching to ADV monotherapy compared to maintaining combination therapy. Methods: This study enrolled 72 patients with undetectable viral loads (≤12 IU/ml) and normal alanine aminotransferase levels after ADV add-on therapy for at least 6 months in LVD-resistant CHB patients. The enrolled patients were randomly assigned to continue with LVD-ADV combination therapy or switch to ADV monotherapy (n = 36 per group). Virological rebound was defined as HBV DNA detection at more than 12 IU/ml by quantitative polymerase chain reaction determined on two consecutive measurements. Results: During 96 weeks of follow-up, 100% (36/36) of the patients in the LVD-ADV combination maintained group had persistently undetectable HBV DNA, compared with 94.4% (34/36) patients in the ADV monotherapy switched group. These two patients had undetectable HBV DNA after switching back to LVD-ADV combination therapy. There were no significant differences in the HBsAg levels between the two treatment groups during the 96-week follow-up period. Conclusions: In our study, switching to ADV monotherapy resulted in sustained HBV DNA suppression in 94.4% of the patients for 96 weeks. Prior complete viral suppression with LVD-ADV combination therapy conferred a significant advantage in patients who switched to ADV monotherapy. LVD may be discontinued in patients who show a complete virological response to LVD-ADV combination therapy for at least 6 months.
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