Effect of cyclosporine on the pharmacokinetics of aliskiren in healthy subjects.

To explore the clinical relevance of inhibition of multidrug resistance transporter 1 and organic anion transporting polypeptide transporter, a drug-drug interaction study was conducted using aliskiren and cyclosporine. This was an open-label, single-sequence, parallel-group, single-dose study in healthy subjects. Subjects (n = 14) first received aliskiren 75 mg orally (period 1), followed by aliskiren 75 mg + cyclosporine 200 mg (period 2) after a 7-day washout period, and aliskiren 75 mg + cyclosporine 600 mg (period 3) after a 14-day washout period.

Human immunodeficiency virus type 1: resistance to nucleoside analogues and replicative capacity in primary human macrophages.

Antiretroviral treatment failure is associated with the emergence of resistant human immunodeficiency virus type 1 (HIV-1) populations which often express altered replicative capacity (RC). The resistance and RC of clinical HIV-1 strains, however, are generally assayed using activated peripheral blood mononuclear cells (PBMC) or tumor cell lines. Because of their high proliferation rate and concurrent high deoxynucleoside triphosphate (dNTP) content, both resistance and RC alterations might be misestimated in these cell systems.

Improved method to quantify intracellular zidovudine mono- and triphosphate in peripheral blood mononuclear cells by liquid chromatography-tandem mass spectrometry.

The determination of intracellular triphosphate metabolites of nucleoside analogs used in anti-HIV therapy is very challenging. Despite the well-known sensitivity and selectivity of LC-MS/MS, the measurement of the triphosphate metabolite of zidovudine (AZT-TP) remains difficult because of the interferences induced by endogenous nucleotides triphosphates. We describe a new approach that allows improved determination of AZT-TP simultaneously with AZT-monophosphate (MP).

Effect of cell cycle arrest on the activity of nucleoside analogues against human immunodeficiency virus type 1.

Human immunodeficiency virus (HIV) reverse transcription can be notably affected by cellular activation, differentiation, and division. We hypothesized that changes in the cell cycle could also affect HIV susceptibility to nucleoside analogues, which compete with natural nucleotides for incorporation into viral DNA and inhibit viral replication through premature termination of reverse transcription. Proliferating HeLa-derived indicator cells were arrested in the S/G2 phase with etoposide, a topoisomerase II inhibitor, or in the G1/S phase with aphidicolin, a polymerase alpha inhibitor.

Development of an assay method for the detection and quantification of protease and non-nucleoside reverse transcriptase inhibitors in plasma and in peripherical blood mononuclear cells by liquid chromatography coupled with ultraviolet or tandem mass spectrometry detection.

We present a simple chromatographic method to detect and quantify protease inhibitors (PI), metabolites and non-nucleoside reverse transcriptase inhibitors (NNRTIs) in human plasma of HIV-1 infected patients and in peripheral blood mononuclear cells (PBMCs) using either liquid chromatography coupled with ultraviolet (LC-UV) or liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). A solid-liquid extraction was carried out on 500 microl of plasma as pre-treatment. Calibration curve ranges were from 50 (100) to 5000 ng/ml (indinavir).

Development and validation of a liquid chromatographic/tandem mass spectrometric assay for the quantitation of nucleoside HIV reverse transcriptase inhibitors in biological matrices.

Besides liquid chromatographic (LC)/UV methods adapted to therapeutic drug monitoring, there is still a need for more powerful techniques that can be used for pharmacological research and clinical purposes. We developed an LC method coupled with tandem mass spectrometry (MS/MS) to separate, detect and quantify with high sensitivity the nucleoside analogues used in multitherapies (zidovudine, stavudine, zalcitabine, didanosine, lamivudine and abacavir) in plasma and in the intracellular medium. We worked on two essential issues: (i) the need to use two ionization modes in order to achieve the best sensitivity, which leads to the optimization of the chromatographic separation of drugs detected in the positive ionization mode and drugs detected in the negative ionization mode, and (ii) the need to optimize the extraction step in order to enhance sample recovery.