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Effect of Entecavir in Patients Who Lack Lamivudine Resistance after Lamivudine Treatment for Chronic Hepatitis B

Background/Aims: The effect of entecavir (ETV) in treatment-naive chronic hepatitis B (CHB) is well established. This study aimed to assess the efficacy of ETV treatment at 0.5 mg/day in ETV-switch and ETV-retreatment groups of CHB patients without lamivudine (LMV)-resistance from LMV monotherapy. Methods: Study subjects included 350 CHB patients who had been treated with 0.5 mg/day of ETV for at least 6 months. Patients were divided into two groups: an LMV-naive group (n = 263) and an LMV-experienced group (n = 87). The LMV-experienced group was further subdivided into an ETV-switch group (n = 43) and an ETV-retreatment group (n = 44) defined by the period between stopping LMV and restarting ETV. Results: There were no significant differences in mean age, sex ratio, prevalence of liver cirrhosis and hepatitis B e antigen (HBeAg) positivity between the LMV-naive and -experienced groups. However, the LMV-naive group had higher aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and a shorter ETV treatment duration than the LMV-experienced group. There were also distributional differences in the hepatitis B virus (HBV) DNA levels of LMV-naive and -experienced patients prior to ETV treatment. After ETV treatment, there were no significant differences between the two groups in the rates of undetectable HBV DNA at 6, 12 and 18 months; HBeAg loss and seroconversion; normalization of ALT; virologic breakthrough; and ETV-genotypic resistance. Lastly, the effect of ETV did not differ between the ETV-switch and -retreatment groups. Conclusions: The effect of ETV in the LMV-experienced group without LMV-resistance did not differ from that in the LMV-naive group. Furthermore, there was no difference in the effect of ETV between the ETV-switch and -retreatment groups. (Korean J Med 2013;84:810-817)