HPLC-MS method for the simultaneous quantification of the new HIV protease inhibitor darunavir, and 11 other antiretroviral agents in plasma of HIV-infected patients

A new method using high performance liquid chromatography coupled with electrospray mass spectrometry (HPLC-MS) was developed and validated, for the quantification of plasma concentration of the new protease inhibitors darunavir (DRV) and other 11 antiretroviral agents (ritonavir, amprenavir, atazanavir, lopinavir, saquinavir, indinavir, nelfinavir and its metabolite M-8, nevirapine, efavirenz and tipranavir). A simple protein precipitation extraction procedure was applied on 50 microl of plasma aliquots and chromatographic separation of drugs and Internal Standard (quinoxaline) was achieved with a gradient (acetonitrile and water with formic acid 0.05%) on an C-18 reverse phase analytical column with 25 min of analytical run. Calibration curves were optimised according to expected ranges of drug concentrations in patients, and correlation coefficient (r2) was higher than 0.998 for all analytes. Mean intra- and inter-day precision (relative standard deviation %) for all compounds were 8.4 and 8.3%, respectively, and mean accuracy (% of deviation from nominal level) was 3.9%. Extraction recovery ranged within 93 and 105% for all drugs analysed. This novel HPLC-MS methodology allows a specific, sensitive and reliable determination of DRV and 11 other antiretrovirals. In our hand, it was used to measure DRV and ritonavir plasma concentration in HIV-positive patients, and it is now successfully applied for routine therapeutic drug monitoring and pharmacokinetics studies.     

Simultaneous determination of nine antiretroviral compounds in human plasma using liquid chromatography

A rapid, sensitive and specific high-performance liquid chromatographic (HPLC) method using UV detection was developed for the determination of nine antiretroviral compounds commonly found in plasma from patients receiving antiretroviral therapy. Analytes include indinavir, saquinavir, ritonavir, amprenavir, lopinavir, delavirdine, efavirenz, nelfinavir and its M8 metabolite. Analytes were isolated from plasma using tert.-butyl methyl ether and separation achieved via reversed-phase liquid chromatography on a C(8) column with a gradient mobile phase. Detection at 210 nm provided adequate sensitivity. Limit of quantification is 50 ng/ml and all analytes demonstrated linearity across 50-10000 ng/ml from a single 200-microliter plasma sample. Recovery from plasma was consistently high (>80%). This novel HPLC methodology allows us to simultaneously determine plasma concentrations of nine antiretrovirals, including lopinavir, in HIV-infected patients on a single HPLC system.     

Monitoring of lopinavir and ritonavir in peripheral blood mononuclear cells, plasma, and ultrafiltrate using a selective and highly sensitive LC/MS/MS assay

For the determination of the HIV protease inhibitors lopinavir and ritonavir in human plasma, plasma ultrafiltrate, and peripheral blood mononuclear cells (PBMCs) a highly sensitive and selective method has been developed, validated, and applied to samples of a healthy volunteer. BD Vacutainer CPT and Amicon Centriplus centrifugal filter devices were used for separation of PBMCs and for ultrafiltrate generation, respectively. After liquid/liquid-extraction extracts were chromatographed isocratically within 6 min on a Jupiter Proteo column. The drugs were quantified using 2H5-saquinavir as internal standard and electrospray tandem mass spectrometry in the selected reaction monitoring mode. Limits of quantification for both analytes were 4.0 ng/mL in plasma, 0.2 ng/mL in ultrafiltrate, and 0.1 ng/cell pellet (approximately 3 x 10(6) cells) in PBMCs. The calibration ranges were linear over more than three logs with an over-all accuracy varying between 98.7% and 111.5% and an over-all precision ranging from 6.2% to 14.0% (SD batch-to-batch). After a regular oral dose of Kaletra (400 mg lopinavir, 100 mg ritonavir) analyte concentrations were detectable over a full dosing interval in plasma, ultrafiltrate, and PBMCs. The method is well suited for monitoring of free and total plasma, and intracellular lopinavir/ritonavir concentrations in samples from clinical trials.     

Sensitive biomonitoring of monoterpene exposure by gas chromatographic-mass spectrometric measurement of hydroxy terpenes in urine

An isocratic reversed-phase high-performance liquid chromatographic method with ultraviolet detection at 205 nm has been validated for the determination of indinavir, ritonavir and lopinavir (ABT 378) in human plasma. The ritonavir analogue A-86093.0 was used as internal standard. Good chromatographic separation was achieved using a stainless steel column packed with 5 microm Phenomenex phenyl hexyl material operated at 40 degrees C, and a mobile phase consisting of acetonitrile-10 mM potassium phosphate buffer (50:50, v/v). The calibration curve for indinavir was linear over the range of 50 to 1000 microg/l while the ritonavir and lopinavir calibration curves were linear over the range of 100 to 15,000 microg/l. The lower limit of quantitations for indinavir, ritonavir and lopinavir were 50, 100 and 100 microg/l, respectively, using 500 microl of human plasma. The validation data showed that the assay is sensitive, specific and reproducible for determination of indinavir, ritonavir and lopinavir. This method is being used in a therapeutic drug monitoring service to quantitate these therapeutic agents in patients infected with human immunodeficiency virus.     

A potent HIV protease inhibitor, darunavir, does not inhibit ZMPSTE24 or lead to an accumulation of farnesyl-prelamin A in cells

HIV protease inhibitors (HIV-PIs) are key components of highly active antiretroviral therapy, but they have been associated with adverse side effects, including partial lipodystrophy and metabolic syndrome. We recently demonstrated that a commonly used HIV-PI, lopinavir, inhibits ZMPSTE24, thereby blocking lamin A biogenesis and leading to an accumulation of prelamin A. ZMPSTE24 deficiency in humans causes an accumulation of prelamin A and leads to lipodystrophy and other disease phenotypes. Thus, an accumulation of prelamin A in the setting of HIV-PIs represents a plausible mechanism for some drug side effects. Here we show, with metabolic labeling studies, that lopinavir leads to the accumulation of the farnesylated form of prelamin A. We also tested whether a new and chemically distinct HIV-PI, darunavir, inhibits ZMPSTE24. We found that darunavir does not inhibit the biochemical activity of ZMPSTE24, nor does it lead to an accumulation of farnesyl-prelamin A in cells. This property of darunavir is potentially attractive. However, all HIV-PIs, including darunavir, are generally administered with ritonavir, an HIV-PI that is used to block the metabolism of other HIV-PIs. Ritonavir, like lopinavir, inhibits ZMPSTE24 and leads to an accumulation of prelamin A.     

Simultaneous determination of HIV protease inhibitors amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in human plasma by high-performance liquid chromatography-tandem mass spectrometry

We report a precise and accurate method for simultaneous quantification of protease inhibitors (PIs) amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in plasma. An internal standard was added to samples prior to protein precipitation with acetonitrile followed by addition of ammonium formate buffer. Analysis was by HPLC-MS/MS. Calibration curves were validated over concentration ranges encompassing both subtherapeutic and potentially 'toxic' drug concentrations. Inter- and intra-assay variation were below 11% and PI recovery was above 87%. The bioanalytical method described is successfully applied to measure PI concentrations obtained from clinical pharmacokinetic studies and routine therapeutic drug monitoring (TDM).