Functional CYP2B6 variants and virologic response to an efavirenz-containing regimen in

virenz trough concentration strata that vary across an 10-fold range. We characterized associations between human genetic polymorphisms and virologic response among participants who received efavirenz-containing regimens in a prospective clinical trial. Methods: We genotyped 76 polymorphisms in CYP2B6 (including those that define efavirenz concentration strata), CYP2A6, CYP3A4, CYP3A5 and ABCB1 and week 48 virologic responses in 360 Haitians who initiated efavirenz-containing regimens in protocol HT 001. Associations were characterized by logistic regression analysis and Fisher’s exact test. Results: Proportions with HIV-1 RNA,50 or,200 copies/mL did not differ across 10 CYP2B6 metabolizer strata. In analyses that combined strata into three metabolizer levels (extensive, intermediate and slow), the respective proportions were 0.79, 0.79 and 0.81 (,50 copies/mL cut-off) and 0.84, 0.86 and 0.87 (,200 copies/mL cut-off). Genetic associations were not identified after controlling for baseline variables or with other polymorphisms after adjusting for multiple comparisons. Conclusions: Virologic failures in HT 001 were not explained by genetic polymorphisms known to define the lowest plasma efavirenz concentration stratum