A comparison of two post-processing analysis methods to quantify cerebral metabolites measured via proton magnetic resonance spectroscopy in HIV disease.

OBJECTIVE: Non-invasive biomarkers to monitor cerebral function in treated human immunodeficiency virus (HIV) disease are required. Cerebral metabolite ratios (CMRs) measured by proton-MR spectroscopy ((1)H-MRS) are a potential biomarker. Here, we compare two post-processing software packages to quantify CMRs. METHODS: Cerebral (1)H-MRS data from 11 HIV-positive subjects before and after antiretroviral therapy intensification with maraviroc were quantified using a java-based version of the MR user interface package (jMRUI) and the totally automatic robust quantitation in nuclear MR (TARQUIN). (1)H-MRS data included N-acetylaspartate (NAA), creatine (Cr), choline (Cho) and myo-inositol (mI) from three cerebral locations. Differences in quantification and clinical associations of CMRs measured by the two packages were evaluated. RESULTS: Mean CMRs were generally lower when measured by TARQUIN than by jMRUI (NAA/Cr, Cho/Cr, mI/Cr ratios of 1.78, 0.83, 0.81 for jMRUI, and 1.27, 0.25, 0.81 for TARQUIN). Longitudinal changes were observed in CMRs in the basal ganglia voxel although these changes were not statistically significant [+7.1% (p = 0.18), +0.0% (p = 0.91) and -6.6% (p = 0.61) and +14.8% (p = 0.18), +17.9% (p = 0.07) and +34.8% (p = 0.17) for NAA/Cr, Cho/Cr and mI/Cr ratios measured by TARQUIN and jMRUI, respectively]. Plasma maraviroc concentration was associated with a decrease in mI/Cr ratio measured via TARQUIN (p = 0.049). CONCLUSION: Although CMRs differed when quantified by jMRUI vs TARQUIN, these differences were consistently observed across three cerebral locations, and clinical associations were evident by both methods. ADVANCES IN KNOWLEDGE: TARQUIN and jMRUI are viable options to use in the post-processing of cerebral MRS data acquired in HIV disease.

Development and bioanalytical validation of a liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the quantification of the CCR5 antagonist maraviroc in human plasma.

BACKGROUND: Maraviroc is a CCR5 antagonist that has been utilized as a viral entry inhibitor in the management of HIV-1. Current clinical trials are pursuing maraviroc drug efficacy in both oral and topical formulations. Therefore, in order to fully understand drug pharmacokinetics, a sensitive method is required to quantify plasma drug concentrations. METHODS: Maraviroc-spiked plasma was combined with acetonitrile containing an isotopically-labeled internal standard, and following protein precipitation, samples were evaporated to dryness and reconstituted for liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis. Chromatographic separation was achieved on a Waters BEH C8, 50×2.1 mm UPLC column, with a 1.7 µm particle size and the eluent was analyzed using an API 4000 mass analyzer in selected reaction monitoring mode. The method was validated as per FDA Bioanalytical Method Validation guidelines. RESULTS: The analytical measuring range of the LC-MS/MS method is 0.5-1000 ng/ml. Calibration curves were generated using weighted 1/x(2) quadratic regression. Inter-and intra-assay precision was ≤5.38% and ≤5.98%, respectively; inter-and intra-assay accuracy (%DEV) was ≤10.2% and ≤8.44%, respectively. Additional studies illustrated similar matrix effects between maraviroc and its internal standard, and that maraviroc is stable under a variety of conditions. Method comparison studies with a reference LC-MS/MS method show a slope of 0.948 with a Spearman coefficient of 0.98. CONCLUSIONS: Based on the validation metrics, we have generated a sensitive and automated LC-MS/MS method for maraviroc quantification in human plasma.