Tenofovir Plus Entecavir vs. Tenofovir in Adefovir-Resistant Chronic Hepatitis B

With the availability of potent nucloes(t)ide analogues (NA), such as tenofovir disoproxil fumarate (TDF) and entecavir (ETV), suppression of serum HBV DNA to undetectable levels by polymerase chain reaction (PCR) assays became achievable in most NA treatment-naïve patients. Until recently, however, many patients commenced antiviral treatment with inferior NAs prior to the availability of TDF or ETV, such as lamivudine (LAM) or adefovir (ADV) which has a low genetic barrier to resistance. For patients who developed genotypic resistance against ADV, the efficacy of TDF monotherapy is controversial. In recent studies, TDF monotherapy produced significant suppression of HBV replication. However, only half of patients with initial ADV resistance achieved an undetectable viral load (\<15 IU/ml) with 48 weeks of therapy. On the other hand, there was a retrospective cohort study reporting that, with the combination of TDF and ETV, most of patients became HBV DNA undetectable after median 6 months of treatment. Probability of reaching complete HBV DNA suppression was not decreased in patients with ADV or ETV resistance. Together, these observations indicate that there is a controversy about the efficacy of TDF monotherapy in patients with genotypic resistance to ADV. Thus, in this clinical trial, the investigators will clarify whether tenofovir monotherapy is effective in inducing complete virologic response compared with tenofovir plus entecavir in CHB patients with genotypic resistance to ADV and partial virologic response to ongoing treatment.