Emerging mutations and associated factors in patients displaying treatment failure on an etravirine-containing regimen.

BACKGROUND: The aim of this study was to characterize the mutations selected upon failure on etravirine (ETR)-containing regimen in non-nucleoside reverse transcriptase inhibitors (NNRTIs)-experienced HIV-infected patients and the associated factors. METHODS: Forty-two patients displaying virological failure after a 6 months ETR-containing regimen were studied. For each patient the reverse transcriptase (RT) sequence at failure was compared with all the RT sequences available before introduction of ETR. The effect of baseline and failure HIV-1 RNA, HIV-1 subtype, baseline number of NNRTI resistance mutations, protease inhibitor and nucleoside RT inhibitor genotypic sensitivity scores, number of new drugs used in the treatment, and previous use of efavirenz or nevirapine on the selection of NNRTI resistance mutations were investigated. RESULTS: At failure, 12/42 (29%) patients showed development of at least 1 new NNRTI mutation (7 patients selected 1 mutation and 5 patients 2 mutations). NNRTI mutations selected were V179I (5 patients), V179L (1), V179F (2), L100I (1), K103N (2), Y181C (3), K101E (1), K101R (1) and H221Y (1). Univariate analysis showed that HIV-1 RNA level at failure (P=0.033) and past exposure to efavirenz (P<0.001) were associated with the occurrence of at least one NNRTI mutation. The multivariate model retained only past exposure to efavirenz. Among the 36 viruses classified as susceptible to ETR at baseline, 3 were classified as possibly resistant at failure. CONCLUSION: In this study, 29% of viruses from patients experiencing ETR failure selected new NNRTI resistance mutations (at position V179 in 2/3 of cases) in a context of multiple NNRTI resistance mutations.