Is Tenofovir Effective in Treatment of Adefovir-Resistant Hepatitis B Virus (HBV) Infections?
F. van Bmmel; B. Zllner; B. Mller; D. Hppe; H. Feucht; B. Wiedenmann; T. Berg Development of HBV resistance against adefovir (ADV) is rare during the first two years of treatment. With increasing treatment duration ADV-resistant HBV mutants are selected (rtN236T; 28% after 5 years) and associated with the risk of a viral breakthrough. In vitro, these mutations cause a 3-14-fold decrease of ADV efficacy. Tenofovir (TDF), a substance closely related to ADV possesses equipotent antiviral activity against HBV on molar basis and is cross resistant to ADV in vitro. However, due to the 25-fold higher dosage of TDF as compared to ADV, TDF might still be effective in ADV resistance. Methods: The efficacy of TDF was evaluated in 3 HBeAg-positive patients (no HIV coinfection) with initial lamivudine resistance and consecutive development of ADV resistance after 22-24 months of ADV monotherapy. When ADV (10 mg/d) was switched to TDF (300 mg/d), the levels of HBV DNA were 7.9, 9.4 and 8 log10 copie
