Efavirenz- and adefovir dipivoxil-based salvage therapy in highly treatment-experienced patients: Clinical and genotypic predictors of virologic response

Objective: To determine the impact of prior nonnucleoside reverse transcrip tase inhibitor (NNRTI) therapy, genotypic resistance, and other variables o n response to efavirenz (EFV)- and adefovir dipivoxil (ADV)-based salvage t herapy. Design: Retrospective clinical cohort study. Setting: One university and one community-based HIV clinic. Study subjects: All 33 patients who were coenrolled in both the EFV and ADV expanded access programs, Interventions: Patients received EFV 600 mg/day and ADV 120 mg/day in,addit ion to other antiretroviral agents. Outcome measure: HIV viral load (<500 c opies/ml) at 12 and 24 weeks. Results: 10 of 33 (30%) patients at 12 weeks and 8 of 33 (24%) patients at 24 weeks had viral loads <500 copies/ml. Prior NNRTI use and a history of a ny NNRTI-associated mutations predicted failure. Patients with Y181C or G19 0A single mutations had an initial greater magnitude of viral load suppress ion than those with K103N, but this advantage was short lived. No one with any NNRTI mutations responded with a viral load <500 copies/ml at 12 or 24 weeks. Conclusions: EFV/ADV-based salvage yielded viral load suppression at 24 wee ks in 42% (8 of 19) of patients who were highly NRTI and protease inhibitor experienced but NNRTI naive. NNRTI-experienced study subjects had a poor r esponse regardless of the specific NNRTI resistance mutation they harbored.