Recommendation of lamivudine-to-entecavir switching treatment in chronic hepatitis B responders: Randomized controlled trial

Prior exposure to lamivudine increases entecavir resistance risk in chronic hepatitis B Patients without detectable lamivudine resistance

The efficacy of entecavir (ETV) treatment in chronic hepatitis B (CHB) patients who were exposed to lamivudine (LAM) but had no detectable LAM resistance (LAM-R) is not well evaluated. In this study, we aimed to evaluate whether the probability of developing genotypic resistance to ETV in LAM-exposed patients with or without LAM-R is comparable to that in antiviral-naive patients. This retrospective cohort study included 500 consecutive patients with CHB who started ETV monotherapy at a single tertiary hospital in Korea. The patients were divided into three groups: nucleos(t)ide analogue (NA)-naive patients (group 1, n=142), patients who were previously exposed to LAM and had no currently or previously detected LAM-R (group 2, n=233), and patients with LAM-R when starting ETV (group 3, n=125). The overall median ETV treatment duration was 48.7 months. The probabilities of virologic breakthrough were significantly increased not only in group 3 (hazard ratio [HR]=14.4, P<0.001) but also in group 2 (HR=5.0, P<0.001) compared to group 1. Genotypic ETV resistance (ETV-R) developed more frequently in group 2 (HR=13.0, P=0.013) as well as group 3 (HR=43.9, P<0.001) than in group 1: the probabilities of developing ETV-R in groups 1, 2, and 3 were <1.0%, 8.0%, and 28.2%, respectively, at month 48. The results of this study indicate that ETV-R occurred more frequently in LAM-exposed patients, even though they had no detectable LAM-R, than in NA-naive patients. Therefore, LAM-exposed CHB patients, regardless of the presence or absence of LAM-R, should be monitored more cautiously for the development of ETV-R during ETV monotherapy.

Treatment of chronic hepatitis B with nucleos(t)ide analogues

Recently antiviral therapies for chronic hepatitis B using nucleos(t)ide analogues have become standard treatment modalities on the basis of several independent guidelines, starting with those of the American Association for the Study of Liver Diseases (AASLD) and other such organizations and bodies, including the European Association for the Study of the Liver (EASL), the Asian Pacific Association for the Study of the Liver (APASL), and the Japanese Ministry of Health, Labour and Welfare (MHLW)'s research team. The philosophies underlying such treatment strategies are considered basically equivalent. MHLW's guidelines define subjects for medical intervention to be cases measuring alanine aminotransferase (ALT) ≥31 IU/L, with serological hepatitis B virus (HBV) DNA level ≥5 log copies/mL for hepatitis B e antigen (HBeAg)-positive cases, and serological HBV DNA level ≥4 log copies/mL for HBeAg-negative cases. These Japanese guidelines advocate entecavir as the first-line treatment option for nucleos(t)ide-naïve patients, and combination treatment of lamivudine and adefovir as the basis of treatment for patients with lamivudine- and/or entecavir-resistant viruses. Of particular note for patients undergoing lamivudine treatment with persistent HBV DNA level < 2.1 log copies/mL is the recommendation of a switch to entecavir. Early detection of drug-resistant virus is desirable after initiation of nucleos(t)ide analogue treatment, but such a procedure is not uniformly available at all medical institutions. Nevertheless, timely estimation of potential early-stage drug-resistant virus development is crucial for getting a head start on treatment. HBV core-related antigen (HBcrAg) level or HBV DNA level are considered useful markers for the appearance of such drug-resistant viruses.