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 Ctrough/fold change in LPV susceptibility, as assessed by VirtualPhenotype) by a reference IQ (mean population LPV Ctrough/fold change in LPV IC50, as assessed by VirtualPhenotype). 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 <80 copies/ml.
Results: The median (interquartile range) baseline levels of CD4+ cells and HIV-1 RNA were 251 (141-385) cells/microl and 4.85 (4.49-5.23) log10 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<0.0001), with 24 subjects (41%) reaching <80 copies/mi. Baseline HIV-1 RNA (P=0.001), CD4+ cells (P=0.002) and NIQ (P=0.0006) independently predicted the week-48 change in viral load, whereas baseline CD4+ cells (P=0.011) and NIQ (P=0.009) independently predicted a week-48 HIV-1 RNA level of <80 copies/ml.
Conclusion: The LPV NIQ independently predicts virological responses to an LPV/RTV-containing regimen in highly treatment-experienced HIV-1-infected patients.