The NIQ of lopinavir is predictive of a 48-week virological response in highly treatment-experienced HIV-1-infected subjects treated with a lopinavir/ritonavir-containing regimen

Objective: To investigate the normalized inhibitory quotient (NIQ) of lopinavir (LPV) as a predictor of 48-week virological responses to a lopinavir/ritonavir (LPV/RTV)-containing regimen in highly treatment-experienced patients. Design: We calculated the NIQ for 59 patients who completed 48 weeks' treatment and assessed the factors predicting a week-48 virological response. Methods: The NIQ was calculated by dividing each subject's IQ (LPV C _trough/fold change in LPV susceptibility, as assessed by Virtua/Phenotype™) by a reference IQ (mean population LPV C _trough/fold change in LPV IC₅₀, as assessed by Virtual Phenotype™). HIV-1 RNA was assessed by NASBA (quantification limit: 80 copies/ml). The general linear model and multiple logistic regression, respectively, were used to estimate the independent predictors of a change in viral load and HIV-1 RNA 10 copies/ml, respectively. The median NIQ was 2.2 (0.5-14). At week 48, the median decrease in HIV-1 RNA was 1.4 (0.59-2.79) log₁₀ copies/ml (P