Two cases of chronic hepatitis B with emergence of lamivudine-resistant virus during long-term therapy

Lamivudine is a potent antiviral drug for chronic hepatitis B, however the emergence of mutant virus resistant to lamivudine has been reported in pati ents with long-term administration of this drug. Here we report two patient s with chronic hepatitis B treated with 48- and 52-weeks administration of lamivudine whose serum hepatitis B virus (HBV) DNA became positive during t herapy. The amino acid sequence of the polymerase region of HBV from these patients revealed a YI/VDD mutation of the YMDD motif and a (223)Leu to Met mutation, which were reported previously in immune suppressed patients dur ing long-term lamivudine therapy for hepatitis B. After the cessation of th erapy, serum HBV-DNA returned to wild-type immediately. Emergence of mutant virus resistant to lamivudine should be monitored during long-term lamivud ine therapy. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.