Comparison of the antiviral activity of adefovir and tenofovir on hepatitis B virus in HIV-HBV-coinfected patients

Background: Characteristics and factors influencing viral decay under tenofovir (TDF) and adefovir (ADV) need to be determined in HIV-HBV-coinfected patients. Methods: This open-label study compared the HBV dynamics in 85 HIV-HBV-coinfected patients initiating an antiretroviral regimen, either including TDF or associated with ADV. The first 6-month change in viral load was analysed using mixed linear models. The adjusted hazards ratio, comparing the rates of undetectable HBV DNA between treatments, was calculated using a Cox proportional hazard model. Results: The HBV DNA decay, adjusted for baseline HBV viral load was more pronounced in patients treated with TDF than with ADV at 12 months (66% Versus 53%, P=0.0001). Patients in the TDF group presented a steeper slope of decline at 1.1 (95% confidence interval [CI] 0.9-1.3), compared with 0.8 (95% CI 0.6-1.0) in the ADV group (P=0.036). The mean time to HBV DNA undetectability was 19.3 months (95% CI 16.7-22.0) with TDF and 25.9 months (95% CI 21.1-30.7) with ADV. When adjusted for hepatitis B virus e antigen, HBV DNA and alanine aminotransferase levels at baseline, the influence of treatment on time to HBV DNA undetectability remained in favour of TDF versus ADV (hazard ratio=2.79, 95% CI 1.05-7.40, P=0.039) Conclusions: TDF influenced more strongly the early-phase HBV DNA kinetics than ADV. This is associated with a sustained antiviral activity in the TDF group, in which patients reached the threshold of HBV undetectability at a faster rate and in a larger proportion than those taking ADV. © 2008 International Medical Press.