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Summary and conclusion<br />
236<br />
fi t model was 93%. There was only a small difference between the effi cacy parameter<br />
of the individual nonlinear fi tting and mixed-effect group fi tting on the biphasic expo-<br />
nential model.<br />
These data show that tenofovir has good effi cacy in blocking viral replication in HBV<br />
patients with lamivudine induced drug-resistant HBV mutants. Both models can be used<br />
to describe viral decay during tenofovir therapy.<br />
Treatment with PEG-IFN α-2b is effective for HBeAg-positive chronic hepatitis B<br />
although its mechanism of action remains unclear. In Chapter 4.3 early pharmaco- and<br />
viral kinetics in patients treated for 52 weeks with PEG-IFN α-2b with or without lamivudine<br />
were analysed. After 4 weeks of treatment, there was a median viral decline of<br />
2.94 log10 copies/ml in those treated with PEG-IFN α-2b and lamivudine and only 0.45<br />
log10 copies/ml in the PEG-IFN α-2b monotherapy group. Peak IFN levels were reached<br />
approximately one day after administration and subsequently declined exponentially<br />
consistent with a viral load rebound near to baseline levels at the end of the dosing<br />
period in most patients receiving PEG-IFN α-2b monotherapy. Modelling of pharmacoand<br />
viral kinetics data in this group revealed that viral load was minimal 3.6 days after<br />
PEG-IFN α-2b administration, the mean maximal and mean antiviral effectiveness was<br />
70% and 48% with a mean infected cell loss rate of 0.07 per day, while no signifi cant<br />
biphasic decline was observed. We conclude that PEG-IFN α-2b induces a sustained<br />
response in a considerable number of patients despite limited direct antiviral activity<br />
during the fi rst weeks of antiviral therapy.<br />
CONCLUSION<br />
For the sustained response 6 months after end of peginterferon (PEG-IFN) treatment of<br />
HBeAg positive chronic hepatitis B patients a prediction model of baseline factors was<br />
designed. This model offers a practical tool to calculate the individual patient prediction<br />
to sustained response and can easily be used in clinical practice to select optimal<br />
candidates for PEG-IFN therapy.<br />
To update the individual response prediction during PEG-IFN therapy in HBeAG positive<br />
chronic hepatitis B patients with the repeated measurements of HBV DNA, assessed<br />
at each visit, dynamic prediction models were developed and different approaches were<br />
compared. The prediction of response to PEG-IFN obtained at baseline can be signifi -<br />
cantly improved with these new methods of dynamic prediction. These methods may be<br />
used to update the prognosis for the individual patients.