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Long‐term monitoring shows hepatitis B virus resistance to entecavir in nucleoside‐naïve patients is rare through 5 years of therapy
Author(s) -
Tenney Daniel J.,
Rose Ronald E.,
Baldick Carl J.,
Pokornowski Kevin A.,
Eggers Betsy J.,
Fang Jie,
Wichroski Michael J.,
Xu Dong,
Yang Joanna,
Wilber Richard B.,
Colonno Richard J.
Publication year - 2009
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1002/hep.22841
Subject(s) - entecavir , lamivudine , hepatitis b virus , virology , genotype , genotyping , drug resistance , nucleoside analogue , medicine , resistance mutation , reverse transcriptase , hepatitis b , biology , virus , nucleoside , polymerase chain reaction , gastroenterology , genetics , gene
Patients with chronic hepatitis B virus (HBV) infection who develop antiviral resistance lose benefits of therapy and may be predisposed to further resistance. Entecavir (ETV) resistance (ETVr) results from HBV reverse transcriptase substitutions at positions T184, S202, or M250, which emerge in the presence of lamivudine (LVD) resistance substitutions M204I/V ± L180M. Here, we summarize results from comprehensive resistance monitoring of patients with HBV who were continuously treated with ETV for up to 5 years. Monitoring included genotypic analysis of isolates from all patients at baseline and when HBV DNA was detectable by polymerase chain reaction (≥300 copies/mL) from Years 1 through 5. In addition, genotyping was performed on isolates from patients experiencing virologic breakthrough (≥1 log 10 rise in HBV DNA). In vitro phenotypic ETV susceptibility was determined for virologic breakthrough isolates, and for HBV containing novel substitutions emerging during treatment. The results over 5 years of therapy showed that in nucleoside‐naïve patients, the cumulative probability of genotypic ETVr and genotypic ETVr associated with virologic breakthrough was 1.2% and 0.8%, respectively. In contrast, a reduced barrier to resistance was observed in LVD‐refractory patients, as the LVD resistance substitutions, a partial requirement for ETVr, preexist, resulting in a 5‐year cumulative probability of genotypic ETVr and genotypic ETVr associated with breakthrough of 51% and 43%, respectively. Importantly, only four patients who achieved <300 copies/mL HBV DNA subsequently developed ETVr. Conclusion: Long‐term monitoring showed low rates of resistance in nucleoside‐naïve patients during 5 years of ETV therapy, corresponding with potent viral suppression and a high genetic barrier to resistance. These findings support ETV as a primary therapy that enables prolonged treatment with potent viral suppression and minimal resistance. (H EPATOLOGY 2009.)