An accelerated background subtraction algorithm for processing high-resolution MS data and its application to metabolite identification.

BACKGROUND: Metabolite identification without radiolabeled compound is often challenging because of interference of matrix-related components. RESULTS: A novel and an effective background subtraction algorithm (A-BgS) has been developed to process high-resolution mass spectral data that can selectively remove matrix-related components. The use of a graphics processing unit with a multicore central processing unit enhanced processing speed several 1000-fold compared with a single central processing unit. A-BgS algorithm effectively removes background peaks from the mass spectra of biological matrices as demonstrated by the identification of metabolites of delavirdine and metoclopramide. CONCLUSION: The A-BgS algorithm is fast, user friendly and provides reliable removal of matrix-related ions from biological samples, and thus can be very helpful in detection and identification of in vivo and in vitro metabolites.

Pharmacokinetic interaction between amprenavir and delavirdine: evidence of induced clearance by amprenavir.

OBJECTIVE: Our objective was to determine the pharmacokinetic interaction between amprenavir and delavirdine. METHODS: Healthy volunteers participated in 2 open-label, 3-period, longitudinal studies. In the first study, 12 volunteers received a single dose of amprenavir, 1200 mg, alone and then again after 7 days of delavirdine, 600 mg twice daily. In the second study, another 12 subjects received amprenavir, 1200 mg twice daily, alone for 7 days. After a 7-day washout period, subjects received delavirdine, 600 mg twice daily, alone for 7 days followed by a combination with amprenavir, 600 mg twice daily, for another 7 days. Amprenavir and delavirdine pharmacokinetics when given alone and in combination were compared. RESULTS: All 12 subjects completed the first study, and 11 subjects completed the second study. Delavirdine significantly increased the area under the curve (AUC) of single-dose amprenavir by 4-fold (P =.0001). Amprenavir, 600 mg twice daily, with delavirdine produced higher levels of amprenavir AUC, minimum concentration (C(min)), and maximum concentration (C(max)), by 30%, 90%, and 18%, respectively, than those of amprenavir, 1200 mg twice daily, alone (P <.05). In contrast, amprenavir decreased delavirdine AUC, C(min), and C(max) by 50%, 70%, and 30%, respectively (P <.005). CONCLUSIONS: Because of the inhibitory effect of delavirdine on the cytochrome P450 3A4-mediated metabolism of amprenavir, the combination of a reduced dose of amprenavir, 600 mg twice daily, with delavirdine resulted in a higher amprenavir exposure than the standard dose of amprenavir, 1200 mg twice daily. However, amprenavir induced the clearance of delavirdine, resulting in a reduction in delavirdine exposure. Further clinical studies are needed to determine the appropriate dosing regimens for delavirdine and amprenavir during coadministration.

Simple and rapid quantification of the non-nucleoside reverse transcriptase inhibitors nevirapine, delavirdine, and efavirenz in human blood plasma using high-performance liquid chromatography with ultraviolet absorbance detection.

A simple reversed-phase high-performance liquid chromatography assay for the simultaneous quantitative determination of three HIV non-nucleoside reverse transcriptase inhibitors (nevirapine, delavirdine, and efavirenz) in human blood plasma is described. The method was validated over the range of 10 ng/ml to 50 microg/ml for nevirapine, 25 ng/ml to 25 microg/ml for delavirdine, and 10 ng/ml to 10 microg/ml for efavirenz. The method is accurate (average accuracies over eight concentrations ranging from 87.3 to 113%), and precise (within-day and between-day precision measures ranging from 0.12 to 7.9% and 0.26 to 5.9%, respectively). All three non-nucleoside reverse transcriptase inhibitors proved to be stable under various conditions. Due to its simplicity, this assay can readily be used for investigational or clinical monitoring of plasma concentrations.

Determination of delavirdine in very small volumes of plasma by high-performance liquid chromatography with fluorescence detection.

Delavirdine is a newly developed anti-HIV-1 drug for AIDS therapy. This study describes a sensitive high-performance liquid chromatographic method for the determination of delavirdine in 50 microl of plasma. Samples were deproteinized with 150 microl of a solution of internal standard (cisapride 10 microg/ml) in acetonitrile. An aliquot of the supernatant was injected onto the column. HPLC separation was achieved on a C18 column with the mobile phase of acetonitrile-50 mM sodium dihydrogen phosphate (60:40, v/v) at a flow-rate of 1 ml/min. The eluants were measured by fluorescence detection with excitation at 295 nm and emission filtration at 425 nm. The retention time was about 5.3 min for delavirdine and 6.5 min for cisapride. The specificity was demonstrated, as there were no interferences from plasma samples of different batches in the regions of peak interest. Calibration curves were linear from 25 to 25000 ng/ml. The limit of quantitation was 25 ng/ml. The within- and between-day precision (C.V.) was 9.3%, or less, and the accuracy was within 9.2% of the nominal concentration. The small sample volume needed is especially advantageous for the application both in pharmacokinetic studies in HIV-infected adults and pediatric patients, and in small animals, where limited samples are available.

Antiretrovirals: simultaneous determination of five protease inhibitors and three nonnucleoside transcriptase inhibitors in human plasma by a rapid high-performance liquid chromatography--mass spectrometry assay.

An analytical technique using liquid chromatography (LC) coupled with electrospray-mass spectrometry (ESI--MS) has been developed for the simultaneous determination of five protease inhibitors (PIs): saquinavir, indinavir, ritonavir, nelfinavir, and amprenavir; and three non-nucleoside reverse transcriptase inhibitors (NNRTIs): nevirapine, delavirdine, and efavirenz, in human plasma. This assay allows the elution and identification of these drugs in a single run (10 minutes) using a linear gradient with water and acetonitrile. The procedure involves liquid--liquid extraction. High-performance liquid chromatography (HPLC) separation was achieved on a C18 reversed-phase column, with a linear gradient elution followed by mass spectrometry detection. The calibration curves, obtained by automatic process peak area integration, show a good linearity in a range of concentrations between 20 and 10,000 ng/mL (40--10,000 ng/mL for efavirenz). The limit of detection was approximately 10 ng/mL for seven drugs (25 ng/mL for efavirenz). The coefficients of variation (CV) were always less than 15% for both intraday and interday precision for each compound. The recovery of the eight drugs ranged from 88.5% to 100%. This novel LC/ESI--MS assay provides an excellent method for simultaneous quantitative monitoring of different components of the highly active antiretroviral treatments (HAARTs) in patients treated simultaneously with PIs and NNRTIs, and it has been successfully applied to therapeutic drug monitoring and pharmacokinetic studies.

Rapid quantification of delavirdine, a novel non-nucleoside reverse transcriptase inhibitor, in human plasma using isocratic reversed-phase high-performance liquid chromatography with fluorescence detection.

Delavirdine is a novel non-nucleoside reverse transcriptase inhibitor for the treatment of HIV-1-infected patients. A simple and rapid high-performance liquid chromatographic method for the quantification of delavirdine in human plasma suitable for drug monitoring in patients is described. Sample pretreatment consists of protein precipitation with acetonitrile and subsequent evaporation of the extract to concentrate the analyte. The drug is separated from endogenous compounds by isocratic reversed-phase, high-performance liquid chromatography coupled with fluorescence detection. The optimal excitation and emission wavelengths are 300 and 425 nm, respectively. The method has been validated over the range of 50-50 000 ng/ml using only 200 microl of plasma samples. The assay is linear over this concentration range as indicated by the F-test for lack of fit. Within- and between-day precisions are less than 4.4% for all quality control samples. The lower limit of quanititation is 50 ng/ml. Recovery of delavirdine from human plasma is 93.8%. Delavirdine is stable under various conditions, for example 1 h at 60 degrees C and one week at 4 degrees C. This validated assay is suited for use in pharmacokinetic studies with delavirdine and can readily be implemented in the setting of a hospital laboratory for the monitoring of delavirdine concentrations.

ACTG 260: a randomized, phase I-II, dose-ranging trial of the anti-human immunodeficiency virus activity of delavirdine monotherapy. The AIDS Clinical Trials Group Protocol 260 Team.

ACTG 260 was an open-label, four-arm trial designed to study the safety and anti-human immunodeficiency virus (anti-HIV) activity of delavirdine monotherapy at three ranges of concentrations in plasma compared to those of control therapy with zidovudine or didanosine. Delavirdine doses were adjusted weekly until subjects were within their target trough concentration range (3 to 10, 11 to 30, or 31 to 50 microM). A total of 113 subjects were analyzed. At week 2, the mean HIV type 1 (HIV-1) RNA level declines among the subjects in the three delavirdine arms were similar (0.87, 1.08, and 1.02 log10 for the low, middle, and high target arms, respectively), but by week 8, the subjects in the pooled delavirdine arms showed only a 0.10 log10 reduction. In the subjects in the nucleoside arm, mean HIV-1 RNA level reductions at weeks 2 and 8 were 0.67 and 0.55 log10, respectively. Because viral suppression by delavirdine was not maintained, the trial was stopped early. Rash, which was usually self-limited, developed in 36% of subjects who received delavirdine. Delavirdine monotherapy has potent anti-HIV activity at 2 weeks, but its activity is time limited due to the rapid emergence of drug resistance.