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Viral dynamics during tenofovir therapy in patients infected with lamivudine-resistant hepatitis B virus mutants


Robert A. de Man, Department of Gastroenterology and Hepatology, Erasmus Medical Center Rotterdam, Room Ca 326, Dr Molewaterplein 40, 3015 GD Rotterdam, The Netherlands.


Summary.  Tenofovir, an antihuman immunodeficiency virus (HIV) drug, has activity against lamivudine-resistant hepatitis B virus (HBV) mutants. To describe the efficacy of tenofovir in patients with lamivudine-resistant hepatitis B we applied two investigative approaches based on mathematical models of viral dynamics: the individual nonlinear fitting and the mixed-effect group fitting approaches.

Eleven chronic HBV patients on lamivudine for a median of 176 weeks (range: 72–382) with YMDD mutation-related HBV-DNA breakthrough received ‘add-on’ tenofovir 300 mg once-daily, while maintaining their existing therapy. Sequential sera were taken at day 1 (t = 0 and t = 8 h), days 2, 4, 7, 10, 14, 21, 28 and every 4 weeks thereafter, and HBV-DNA levels were assessed using a validated quantitative polymerase chain reaction (PCR) assay.

Median baseline log HBV-DNA was 8.62 (range: 6.48–9.76 log HBV-DNA). Tenofovir treatment resulted in a mean (±SD) log HBV-DNA decline of 1.37 ± 0.51 in the first phase, 2.54 ± 0.91 after 4 weeks, and 4.95 ± 0.90 log HBV-DNA after 24 weeks. The median effectiveness of blocking viral replication in the individual fit model was 93% (range: 73–99) for η = 0 and 93% (range: 59–99) for η = 1. There was only a small difference between the efficacy parameter ‘ɛ’ of the individual nonlinear fitting and mixed-effect group fitting on the biphasic exponential model.

These data show that tenofovir has good efficacy in blocking viral replication in HBV patients with lamivudine-induced drug-resistant HBV mutants, but effectiveness varies greatly among individuals. Both models can be used to describe viral decay during tenofovir therapy.