title: Successful treatment of an entecavir-resistant hepatitis B virus variant.
abstract: Emergence of a lamivudine (LAM)-resistant hepatitis B virus (HBV) with amino acid substitutions in the YMDD motif is a well-documented problem during long-term LAM therapy. Entecavir (ETV) is a new drug approved for treatment of HBV infection with or without LAM-resistant mutants. This report describes an ETV-resistant strain of HBV, which emerged after prolonged ETV therapy in a patient who did not respond to LAM therapy. Direct sequence analysis of the ETV-resistant strain showed appearance of amino acid substitution rtS202G in the reverse transcriptase (RT) domain, together with rtL180M + M204V substitution that had developed at the emergence of LAM-resistant mutant. In vitro analysis demonstrated that the rtL180M + M204V + S202G mutant strain displayed a 200-fold and a 5-fold reduction in susceptibility to ETV compared with the wild- type and the rtL180M + M204V mutant strain, respectively. Adefovir was effective against the ETV-resistant strain both in vitro and during the clinical course. In conclusion, this study showed that virological and biochemical breakthrough due to ETV could occur in patients infected with LAM-resistant HBV and confirmed that the addition of rtS202G substitution to the rtL180M + M204V mutant strain is responsible for ETV resistance and we could treat the resistant mutant successfully.
authors.affiliation: Department of Medicine and Molecular Science, Division of Frontier Medical Science, Programs for Biomedical Research, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Yatsuji
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Hiraga
authors.forename: Nami
authors.initials: N
authors.lastname: Mori
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Hatakeyama
authors.forename: Masataka
authors.initials: M
authors.lastname: Tsuge
authors.forename: Michio
authors.initials: M
authors.lastname: Imamura
authors.forename: Shoichi
authors.initials: S
authors.lastname: Takahashi
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Hidenori
authors.initials: H
authors.lastname: Ochi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Abe
authors.forename: Toshiro
authors.initials: T
authors.lastname: Maekawa
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Suzuki
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Kumada
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Chayama
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000627:therapeutic use; D000328:Adult; D000998:Antiviral Agents / Q000494:pharmacology; D004334:Drug Administration Schedule; D024921:Drug Resistance, Multiple, Viral; D005260:Female; D006147:Guanine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D006509:Hepatitis B / Q000188:drug therapy* / Q000821:virology*; D006515:Hepatitis B virus / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology; D009154:Mutation; D063065:Organophosphonates / Q000627:therapeutic use; D019562:Viral Load
chemical_list: D000998:Antiviral Agents; D063065:Organophosphonates; D019259:Lamivudine; C413685:entecavir; D006147:Guanine; C053001:adefovir; D000225:Adenine