Phenotypic HIV-1 resistance correlates with treatment outcome of nelfinavir salvage therapy

In order to analyse whether drug sensitivity testing would be beneficial fo r clinical decision-making in heavily pretreated patients, we retrospective ly studied viral genotype and phenotypic drug resistance in 12 HIV-1-infect ed patients, each of them with a history of failing at least one therapeuti c regimen including one or two protease inhibitors (PIs). The salvage thera py included nelfinavir as new PI in all cases. Four patients showed a susta ined and five patients a transient viral load decrease. Three patients fail ed to show a significant decline of plasma HIV-1 RNA. In the baseline sampl es of these cases, resistance against all components of their combination t herapy could be detected, whereas at least one antiretroviral drug was stil l active in the cases with transient treatment response. All patients with sustained therapy response harboured viruses that were either fully sensiti ve or resistant to only one of the drugs administered. In our study, phenot ypic drug resistance was predictive for the success of antiretroviral salva ge regimens.