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Viral dynamics during tenofovir therapy 201
response appeared to be due to the existence of complex multiphasic decay patterns in
some patients. Therefore, as for the early viral kinetics, the rate of viral decay in the fi rst
4 weeks of treatment did not appear to determine the rate of viral decay in the following
phase (the next 20 weeks of treatment).
DISCUSSION
This study provides the fi rst detailed viral kinetic data following tenofovir treatment of
patients with drug-resistant HBV mutants. Previous modelling studies in chronic-infected
HBV patients have demonstrated that a biphasic pattern of viral response occurs during
the fi rst 4 weeks of antiviral treatment with nucleoside analogues. 19 In the study reported
here, the viral decay in patients treated with tenofovir showed a similar biphasic pattern
of early viral response. However, after 4 weeks, treatment response was less predictable
and a variety of patterns of viral decay were observed, a fi nding that is similar to the
patterns of viral decay previously found following adefovir treatment. 18
The effectiveness of tenofovir, as calculated with the individual fit, was 0.926. This is
much lower than the reported effi cacy of adefovir in treatment-naive patients, which
was 0.993 ± 0.008 (mean ± SE; median: 0.996), 24 but was comparable with the effi cacy of
0.928 (±0.015 SE) for lamivudine. 19
Also of note is that the duration of the fi rst-phase is