Joanna Yang

Long‐term monitoring shows hepatitis B virus resistance to entecavir in nucleoside‐naïve patients is rare through 5 years of therapy

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 log10 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. (HEPATOLOGY 2009.)

Two-Year Assessment of Entecavir Resistance in Lamivudine-Refractory Hepatitis B Virus Patients Reveals Different Clinical Outcomes Depending on the Resistance Substitutions Present

ABSTRACT Entecavir (ETV) is a deoxyguanosine analog approved for use for the treatment of chronic infection with wild-type and lamivudine-resistant (LVDr) hepatitis B virus (HBV). In LVD-refractory patients, 1.0 mg ETV suppressed HBV DNA levels to below the level of detection by PCR (<300 copies/ml) in 21% and 34% of patients by Weeks 48 and 96, respectively. Prior studies showed that virologic rebound due to ETV resistance (ETVr) required preexisting LVDr HBV reverse transcriptase substitutions M204V and L180M plus additional changes at T184, S202, or M250. To monitor for resistance, available isolates from 192 ETV-treated patients were sequenced, with phenotyping performed for all isolates with all emerging substitutions, in addition to isolates from all patients experiencing virologic rebounds. The T184, S202, or M250 substitution was found in LVDr HBV at baseline in 6% of patients and emerged in isolates from another 11/187 (6%) and 12/151 (8%) ETV-treated patients by Weeks 48 and 96, respectively. However, use of a more sensitive PCR assay detected many of the emerging changes at baseline, suggesting that they originated during LVD therapy. Only a subset of the changes in ETVr isolates altered their susceptibilities, and virtually all isolates were significantly replication impaired in vitro. Consequently, only 2/187 (1%) patients experienced ETVr rebounds in year 1, with an additional 14/151 (9%) patients experiencing ETVr rebounds in year 2. Isolates from all 16 patients with rebounds were LVDr and harbored the T184 and/or S202 change. Seventeen other novel substitutions emerged during ETV therapy, but none reduced the susceptibility to ETV or resulted in a rebound. In summary, ETV was effective in LVD-refractory patients, with resistant sequences arising from a subset of patients harboring preexisting LVDr/ETVr variants and with approximately half of the patients experiencing a virologic rebound.

Efficacy and safety of entecavir in patients with chronic hepatitis B and advanced hepatic fibrosis or cirrhosis.

OBJECTIVE: The efficacy and safety of entecavir in patients with chronic hepatitis B and advanced liver fibrosis/cirrhosis was assessed from three large, randomized, multicenter, phase III studies.PATIENTS AND METHODS:These studies enrolled patients (≥16 yr) with chronic hepatitis B, elevated alanine aminotransferase (ALT) levels, and compensated liver disease. Two trials enrolled nucleos(t)ide-naive patients randomized to at least 48 wk of treatment with entecavir 0.5 mg/day or lamivudine 100 mg/day. The third trial randomized lamivudine-refractory patients to 48 wk of entecavir 1 mg/day or lamivudine 100 mg/day. In this post hoc descriptive analysis, the efficacy and safety in patients with advanced liver fibrosis/cirrhosis (Ishak fibrosis stages 4–6) were examined for consistency with those seen in the overall study populations.RESULTS: Of the 1,633 treated patients, 245 had advanced liver fibrosis/cirrhosis (120 entecavir and 125 lamivudine). Among entecavir-treated patients with advanced liver fibrosis, improvement in Ishak fibrosis was observed in 57% of nucleos(t)ide-naive hepatitis B e antigen (HBeAg)-positive patients, 59% of nucleos(t)ide-naive HBeAg-negative patients, and 43% of lamivudine-refractory HBeAg-positive patients versus 49%, 53%, and 33% of lamivudine-treated patients with advanced liver fibrosis. The overall trends in other histologic, virologic, biochemical, and serologic outcomes in entecavir- versus lamivudine-treated patients with advanced liver fibrosis/cirrhosis were consistent with those observed in the overall study populations in each trial. The treatment was well tolerated.CONCLUSION: These data confirm that the performance of entecavir relative to that of lamivudine in patients with advanced liver fibrosis/cirrhosis was consistent with the relationship observed in the overall treated population.

Sofosbuvir plus ribavirin for the treatment of patients with chronic genotype 1 or 6 hepatitis C virus infection in Hong Kong

In Hong Kong, most patients with hepatitis C virus (HCV) have either genotype 6a or 1b infection.