Evolution of hepatitis B virus during long-term therapy in patients with chronic hepatitis B.

BACKGROUND: Long-term lamivudine (LAM), adefovir (ADV) and entecavir (ETV) treatment induce the emergence of drug-resistant hepatitis B virus (HBV) in patients with chronic hepatitis B infection. AIM: To evaluate the LAM, ADV and ETV resistance mutations detected in our patient group. MATERIALS AND METHODS: Twenty patients who had received at least two years of treatment with nucleoside/tide analogues were enrolled in this study. Patients with detectable HBV DNA were analyzed in order to detect resistance mutations and in this group of patients treatment was change. RESULTS: Three patients developed LAM resistance mutations (2 presented rtM204I and one rtL180M+rtM204V/I) and one patient showed rtN236T ADV resistance mutation. During ADV and LAM treatment, one patient developed ADV plus LAM resistance mutations (rtI163V+rtL180M+rtA181V+rtN236T), in this case, HBV strains harbouring polymerase mutations did not develop LAM associated rtM204V/I primary mutation. In addition, ETV resistance mutations (rtL180M+rtT184A+rtS202G+rtM204V) were detected in one patient. CONCLUSIONS: These findings suggest that monotherapy resulted in a limited virological response and combination strategies including potent antiviral agents should be recommended for patients with resistant mutations.