Hydroxyethylamine derivatives as HIV-1 protease inhibitors: a predictive QSAR modelling study based on Monte Carlo optimization

Application of HIV-1 protease inhibitors (as an anti-HIV regimen) may serve as an attractive strategy for anti-HIV drug development. Several investigations suggest that there is a crucial need to develop a novel protease inhibitor with higher potency and reduced toxicity. Monte Carlo optimized QSAR study was performed on 200 hydroxyethylamine derivatives with antiprotease activity. Twenty-one QSAR models with good statistical qualities were developed from three different splits with various combinations of SMILES and GRAPH based descriptors. The best models from different splits were selected on the basis of statistically validated characteristics of the test set and have the following statistical parameters: r² = 0.806, Q² = 0.788 (split 1); r² = 0.842, Q² = 0.826 (split 2); r² = 0.774, Q² = 0.755 (split 3). The structural attributes obtained from the best models were analysed to understand the structural requirements of the selected series for HIV-1 protease inhibitory activity. On the basis of obtained structural attributes, 11 new compounds were designed, out of which five compounds were found to have better activity than the best active compound in the series.

Antibacterial, anti-HIV-1 protease and cytotoxic activities of aqueous ethanolic extracts from Combretum adenogonium Steud. Ex A. Rich (Combretaceae)

BACKGROUND

Records have shown that Combretum adenogonium Steud. Ex A. Rich (Combretaceae) is used in traditional medicine systems of several tribes in Tanzania. This study focused on the investigation of antibacterial activity, anti-HIV-1 protease activity, toxicity properties and classes of phytochemicals in extracts from C. adenogonium Steud. Ex A. Rich (Combretaceae) to evaluate potential of these extracts for development as herbal remedies.

METHODS

Dried plant material were ground to fine powder and extracted using 80% aqueous ethanol to afford root, leaf and stem bark extracts. The extracts were assayed for anti-HIV-1 protease activities, antibacterial activities using microdilution methods and cytotoxicity using brine shrimps lethality assay. Screening for major phytochemical classes was carried out using standard chemical tests.

RESULTS

All extracts exhibited antibacterial activity to at least one of the test bacteria with MIC-values ranging from 0.31-5.0 mg/ml. Two extracts, namely, root and stem bark exhibited anti-HIV-1 PR activity with IC50 values of 24.7 and 26.5 μg/ml, respectively. Stem bark and leaf extracts showed mild toxicity with LC50 values of 65.768 μg/ml and 76.965 μg/ml, respectively, whereas roots were relatively non-toxic (LC50 = 110.042 μg/ml). Phytochemical screening of the extracts indicated presence of flavonoids, terpenoids, alkaloids, tannins, glycosides and saponins.

CONCLUSION

These results provide promising baseline information for the potential development of C. adenogonium extracts in treatment of bacterial and HIV/AIDS-related opportunistic infections.

A mass spectrometry based imaging method developed for the intracellular detection of HIV protease inhibitors

Mass spectrometry imaging is a promising technique for measuring drugs and drug metabolites in cells and tissues. In this manuscript we describe a method for the imaging of HIV protease inhibitors. As a model system we used Mono Mac 6 cells cultured with the HIV protease inhibitors saquinavir and nelfinavir deposited on glass slides using a cytocentrifuge. A sublimation/deposition device for homogeneous matrix deposition was constructed which allows imaging of these HIV protease inhibitors at clinically relevant concentrations. Using this matrix sublimation/deposition method, glass slides containing the cytocentrifuged cells can be measured and analyzed by two types of mass spectrometry techniques, viz. matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and MALDI Fourier transform ion cyclotron resonance (FTICR), and this makes it possible to perform imaging rapidly (MALDI-TOF) and with a very high selectivity (MALDI-FTICR).

Quality Control of Protease Inhibitors

Protease inhibitors (PIs) are potent competitive inhibitors of the human immunodeficiency virus (HIV) widely used in the treatment of the acquired immune deficiency syndrome (AIDS) and prescribed in combination with other antiretroviral drugs. So far ten PIs were approved by the United States Food and Drug Administration (FDA) for the treatment of HIV infection. In this mini review, quality control methods of each PI are discussed on the basis of analytical techniques published in the literature. Special attention is given to summarize the LC methods described for the analysis of the selected PIs in both drug substances and products with the available literature till date.

Same patient, new stone composition: amprenavir urinary stone

We report here the first case to add amprenavir to the growing list of antiretroviral drugs associated with urinary stones. The first reported case of a nelfinavir urinary stone was reported in 2002 in a 37-year-old HIV-infected woman. In September 2007, the same female patient was referred to our department with recent onset of right flank pain and recurrent urinary tract infections. Abdominal computed tomography revealed three obstructing stones in the distal right ureter, another stone in the right renal pelvis with hydronephrosis and a stone in the left kidney. After stone retrieval, analysis of the stone by liquid chromatography with mass spectrometry revealed a stone composition of 95% unmodified amprenavir and 5% ritonavir.

The role of compartment penetration in PI-monotherapy: the Atazanavir-Ritonavir Monomaintenance (ATARITMO) Trial

OBJECTIVES

To limit exposure to anti-HIV drugs and minimize risk of long-term side effects, studies have looked at the possibility of simplified maintenance strategies. Ritonavir-boosted protease-inhibitor (PI)-monotherapies are an attractive alternative, but limited compartmental penetration of PI remains a concern.

DESIGN

Non-comparative 24-week pilot study.

METHOD

Ritonavir-boosted atazanavir (ATV/r) monotherapy administered to fully suppressed patients (>3 month HIV RNA < 50 copies/ml). Plasma was obtained every 4 weeks and cerebrospinal fluid (CSF) and semen at W24.

RESULTS

Two patients (7%) failed ATV/r monotherapy. One patient was subsequently identified as a protocol violator since he had a previous history of treatment failure under indinavir. The second patient deliberately decided to stop treatment after W20. Excluding failing patients, individual measurements of HIV RNA in patients having occasional viral 'blips' was found in five patients. At W24, 3/20 patients had elevated viral loads in CSF (HIV RNA > 100 copies/ml), and 2/15 in semen, despite viral suppression in plasma (< 50 copies/ml). Samples with elevated HIV RNA (> 500 copies/ml) in CSF were all wild type. The mean ATV drug concentration ratio (CSF/blood, n = 22) was 0.9%. Indicators of altered immune activation (CD8CD38 C-reactive protein) remained unchanged.

CONCLUSION

This study supports previous results indicating the potential use of PI-based mono-maintenance therapies. However, our results in CSF cautions against the uncontrolled use of PI-based monotherapies.

A novel validated LC method for quantitation of lopinavir in bulk drug and pharmaceutical formulation in the presence of its potential impurities and degradation products

A simple isocratic liquid chromatographic method was developed for determination of lopinavir from its related impurities and assay for the first time. This method involves the use of a C(8) (Symmetry Shield RP8, 150 x 4.6 mm, 5 microm) column. The method was validated over the range of limit of quantitation (LOQ) to 120% of impurity specification limit and LOQ to 150% of working concentration for assay. The mobile phase consisted of a mixture of 50 mM of potassium phosphate buffer, acetonitrile and methanol in the ratio of 40:50:10. The flow rate was set at 1.0 mL/min with UV detection monitored at 210 nm. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation. The developed method was validated for linearity, range, precision, accuracy and specificity. This method was successfully applied for content determination of lopinavir in pharmaceutical formulations. The method can be conveniently used in a quality control laboratory for routine analysis for assay and related substances as well for the evaluation of stability samples of bulk drugs and pharmaceutical formulations.

Quantitative immunoassay to measure plasma and intracellular atazanavir levels: analysis of drug accumulation in cultured T cells

We have developed an enzyme immunoassay to measure atazanavir (ATV) levels in plasma and cells. Anti-ATV polyclonal antibodies were raised in rabbits by using a synthetic ATV derivative coupled to bovine serum albumin as the immunogen, and the enzyme tracer was prepared by chemically coupling the ATV derivative with acetylcholinesterase. These reagents were used to develop a sensitive competitive enzyme immunoassay performed in microtitration plates, and the lowest limit of quantification was 150 pg/ml, which is about 10 times more sensitive than previously published techniques. The plasma assay was performed, after a simple methanol extraction, with a minimum of 30 microl of plasma. This assay showed good precision and efficiency, since the rates of recovery from human plasma and cell extracts spiked with ATV ranged form 93 to 113%, with coefficients of variation of less than 10%. ATV concentrations were measured in peripheral blood mononuclear cells incubated with various ATV concentrations and in CEM cells in the absence or presence of antiretroviral drugs and drug transporter inhibitors. The results indicated a dose-dependent uptake (intracellular concentration/extracellular concentration ratio range, 0.04 to 19). A significant increase in the accumulation of ATV was noticed in the presence of P-glycoprotein and MRP1 inhibitors (dipyridamole, inter alia). Interestingly, efavirenz significantly increased the baseline accumulation of ATV, whereas nevirapine induced a marked reduction. This new enzyme immunoassay for measuring plasma and intracellular ATV levels was fully validated and provides an inexpensive and useful tool for routine therapeutic drug monitoring. Moreover, in vitro results suggested the implication of drug transporters and interactions with other antiviral drugs that should be further explored in human immunodeficiency virus-infected patients.

Qualitative and Quantitative Analysis of Pharmaceutical Compounds by MALDI-TOF Mass Spectrometry

In this report, we discuss key issues for the successful application of MALDI-TOF mass spectrometry to quantify drugs. These include choice and preparation of matrix, nature of cationization agent, automation, and data analysis procedures. The high molecular weight matrix meso-tetrakis(pentafluorophenyl)porphyrin eliminates chemical noise in the low-mass range, a "brushing" spotting technique in combination with prestructured target plates enables fast preparation of homogeneous matrix crystals, and addition of Li+ leads to intense cationized drug species. Complex biological samples were cleaned up using a 96-well solid-phase extraction plate, and the purified samples were automatically spotted by a pipetting robot. To obtain a suitable data analysis procedure for the quantitative analysis of drugs by MALDI-TOF mass spectrometry, various data processing parameters were evaluated on our two model drugs lopinavir and ritonavir. Finally, and most importantly, it is shown that the above-described procedure can be successfully applied to quantify clinically relevant concentrations of lopinavir, an HIV protease inhibitor, in extracts of small numbers of peripheral blood mononuclear cells (1 x 10(6)).

Determination of nelfinavir mesylate as bulk drug and in pharmaceutical dosage form by stability indicating HPLC

A isocratic, selective, accurate and stability indicating HPLC method of analysis of nelfinavir mesylate both as a bulk drug and in formulations was developed and validated. A CN chromatographic column (250 mmx4.6 mm, 5 microm) was used for the separation at 40 degrees C. The mobile phase consisted of a mixture of acetonitrile (MeCN) and 25 mM monobasic ammonium phosphate (containing 25 mM triethylamine, pH 3.4 with phosphate acid) (40:60, v/v) was delivered at a flow rate of 1.0 ml/min with detection at 210 nm. The developed method was validated in terms of selectivity, linearity, limit of quantitation, precision, accuracy and solution stability. As the proposed LC method achieved satisfactory resolution between nelfinavir mesylate, its degradation products, intermediate product possibly present in nelfinavir drug substance and other impurities in the end product before refining in the final step of synthetic process, it can be employed as a stability indicating one, used for the synthetic process control and determination of nelfinavir mesylate in pharmaceutical preparations.

Electrochemical methods for determination of the protease inhibitor indinavir sulfate in pharmaceuticals and human serum

Indinavir sulfate is an inhibitor of the human immunodeficiency virus (HIV) protease. The aim of this study was to determine indinavir levels in serum and pharmaceuticals, by means of electrochemical methods using the hanging mercury drop electrode (HMDE). Indinavir exhibited irreversible cathodic waves over the pH range 2.00-12.00 in different supporting electrolytes. The current-concentration plot was rectilinear over the range from 8 x 10(-7) M to 8 x 10(-6) M with a correlation coefficient of 0.996 for differential pulse voltammetry (DPV) and 8 x 10(-7) M to 1 x 10(-5) M with correlation of 0.999 M for osteryoung square ware voltammetry (OSWV) in Britton-Robinson buffer at pH 10.00. The wave was characterized as being irreversible and diffusion-controlled. The proposed methods were fully validated and successfully applied to the determination of indinavir in capsules and spiked human serum samples with good recoveries. The repeatability and reproducibility of the methods as well as precision and accuracy (such as supporting electrolyte, serum samples) were determined. No electroactive interferences from the endogenous substances were found in serum samples.

LC–MS/MS determination of the HIV-1 protease inhibitor indinavir in brain and testis of mice

A rapid and sensitive method for the determination of indinavir in mice brain and testis is described and validation data are provided. Indinavir and the internal standard (IS) amprenavir were isolated from homogenized tissue matrices using a mixed-mode solid-phase extraction (SPE) procedure and were then analyzed by reversed-phase liquid chromatography/tandem mass spectrometry (LC-MS/MS). The mass spectrometer in the positive-ion multiple reaction monitoring mode used pairs of ions at m/z of 614.1/421.3 for indinavir and of 506.1/245.3 for IS. The calibration curves were linear over the range 0.0012-0.0390 micromol/kg for brain and 0.39-12.50 micromol/kg for testis. Linearity, repeatability and accuracy were validated. The applicability of the method was demonstrated by assessing indinavir in brain and testis of three mice dosed with intravenous bolus administration of indinavir (16.3 micromol/kg).

HPLC quantification of the HIV-1 protease inhibitor saquinavir in brain and testis of mice

A rapid, reliable HPLC method with UV detection (240 nm) was developed and validated for quantitation of saquinavir in mice brain and testis. Saquinavir and the internal standard were isolated from homogenized tissue matrices using liquid-liquid extraction procedure and were then analyzed using an isocratic mobile phase by reversed-phase liquid chromatography. The lower limit of quantification was 50 ng/g for both brain and testis. A linear dynamic range of 50-5000 ng/g for both brain and testis was established. This HPLC method was validated with between-batch precision of 0.5-4.4 and 1.5-5.5% for brain and testis, respectively. The between-batch accuracy was 94.7-105.9% and 97.5-105.0% for brain and testis, respectively. The present method was applied for tissue distribution studies of the novel drug delivery systems of saquinavir in mice.

Determination of atazanavir in human plasma using solid-phase extraction and high-performance liquid chromatography

Atazanavir is a new HIV-1 protease inhibitor. A simple high-performance liquid chromatographic method using UV detection was developed and validated for the analysis of atazanavir in human plasma. The sample clean up was carried out using solid-phase extraction with OASIS MCX cartridge. The chromatographic separation was achieved on a Kromasil C18 (150 mm x 3 mm, 5 microm) column with a mobile phase consisting of acetonitrile and water (38:62 v/v) delivered isocratically. The effluent of the column was monitored at a wavelength of 210 nm. The assay was linear over the concentration range of 0.156 to 10 microg/ml and the limit of quantification was 0.156 microg/ml. The method was also validated with respect to recovery, precision, accuracy and specificity. This method is suitable for therapeutic drug monitoring of atazanavir and can be easily reproduced with standard equipment.

Bioanalysis of HIV protease inhibitors in samples from sanctuary sites

The human immunodeficiency virus (HIV) is present in several sites inside the human body, which are hardly accessible to antiretroviral drugs, the so-called sanctuary sites. The most important sanctuary sites are cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMCs) and seminal plasma. The determination of drug concentrations in these sanctuary sites may form an important step in treatment optimisation of HIV-infected individuals. However, bioanalysis in these sites is hampered by several factors with regard to sample preparation, chromatography and detection. In this review, we will discuss these issues and give an overview of published methods using high-performance liquid chromatography (HPLC) for the bioanalysis of HIV protease inhibitors in CSF, PBMCs and seminal plasma.

Directed evolution of PDZ variants to generate high-affinity detection reagents

High-throughput protease assays are used to identify new protease inhibitors which have the potential to become valuable therapeutic products. Antibodies are of great utility as affinity reagents to detect proteolysis products in protease assays, but isolating and producing such antibodies is unreliable, slow and costly. It has been shown previously that PDZ domains can also be used to detect proteolysis products in high-throughput homogeneous assays but their limited natural repertoire restricts their use to only a few peptides. Here we show that directed evolution is an efficient way to create new PDZ domains for detection of protease activity. We report the first use of phage display to alter the specificity of a PDZ domain, yielding three variants with up to 25-fold increased affinity for a peptide cleavage product of HIV protease. Three distinct roles are assigned to the amino acid substitutions found in the selected variants of the NHERF PDZ domain: specific 'beta1-beta3' interaction with ligand residue -1, interactions with ligand residues -4 to -7 and improvement in phage display efficiency. The variants, having affinities as high as 620 nM, display improvements in assay sensitivity of over 5-fold while requiring smaller amounts of reagents. The approach demonstrated here leads the way to highly sensitive reagents for drug discovery that can be isolated more reliably and produced less expensively.

Determination of the new HIV-protease inhibitor atazanavir by liquid chromatography after solid-phase extraction

An HPLC method previously described for the simultaneous assay of amprenavir, ritonavir, indinavir, saquinavir, nelfinavir and efavirenz is proposed here for the simultaneous analysis of the new HIV protease inhibitor atazanavir (ATV) in human plasma, by off-line solid-phase extraction (SPE) followed by HPLC coupled with UV-diode array detection. After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl) with clozapine (internal standard) is diluted 1 + 1 with phosphate buffer pH 7 and subjected to a SPE on a C18 cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H(3)PO(4) neutralised with NaOH to pH 7. ATV is eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl MeOH/H(2)O 50/50. A 40 microl volume is injected onto a Nucleosil 100-5 microm C18 AB column. ATV is analysed by UV detection at 201 nm using a gradient elution program with solvents constituted of MeCN and phosphate buffer adjusted to pH 5.14. The mobile phase also contains 0.02% sodium heptanesulfonate, enabling an excellent separation of ATV from the other HIV protease inhibitors (PIs) amprenavir, indinavir, saquinavir, ritonavir, lopinavir, nelfinavir and the non-nucleoside reverse transcriptase inhibitors (NNRTIs) efavirenz and nevirapine. The calibration curves are linear up to 10 microg/ml, with a lower limit of quantification of 0.2 microg/ml. The mean absolute recovery of ATV is 96.4 +/- 3.2%. The method is precise with mean inter-day CVs within 1.1-6.1%, and accurate (range of inter-day deviations +0.3 to +2.3%). The method has been validated and is currently applied to the monitoring of ATV in HIV patients.

An enzyme immunoassay for the quantification of plasma and intracellular lopinavir in HIV-infected patients

The protease inhibitor lopinavir (LPV; [1S-[1R*(R*), 3R*,4R*]]-N-[4-[[(2,6-dimethylphenoxy)-acetyl]amino]-3-hydroxy-5-phenyl-1-(phenylmethyl) pentyl] tetrahydro-alpha-(1-methylethyl)-2-oxo-1(2H)-pyrimide acetamide) is widely used in anti-human immunodeficiency virus (HIV) therapy. Knowledge of the plasma and intracellular concentrations of the drug would be useful for a better understanding of LPV action and for therapeutic monitoring. The aim of this study was to develop a sensitive and specific immunoassay for LPV in plasma and cells. Anti-LPV polyclonal antibodies were raised in rabbits using a synthetic LPV derivative coupled to keyhole limpet hemocyanin (KLH) as immunogen. The enzyme tracer was prepared by chemically coupling the LPV derivative with acetylcholinesterase. These reagents were used to develop a competitive enzyme immunoassay (EIA) performed in microtitration plates. The assay was performed on a minimum of 50 microl of plasma or 2 x 10(6) cells. It showed good precision and efficiency in as much as recovery from human plasma and cell extracts spiked with LPV ranged between 87% and 104%, with coefficients of variation of less than 10%. The limit of detection (LOD) was 100 pg/ml, i.e., a value at least 10 times lower than those currently achieved using previously described techniques. Cross-validation with high-performance liquid chromatography (HPLC) revealed a good correlation between methods (r2=0.96). Intracellular concentrations of LPV were measured in cultured human T lymphoblastoid cells (CEM). A pharmacokinetic analysis of plasma and intracellular LPV was performed on a healthy volunteer, and measurements were done in patients infected with HIV. The results obtained indicated a high intracellular/extracellular concentration ratio in cultured cells (19.3) but not in cells from HIV patients (1.3). In contrast, in peripheral blood mononuclear cells (PBMC) the accumulation of ritonavir (RTV) was six times higher than LPV. To date, this is the first reported immunoassay for LPV, and this method is sensitive enough for monitoring plasma and intracellular LPV levels in HIV-infected patients and for intracellular studies.

Insights into saquinavir resistance in the G48V HIV-1 protease: quantum calculations and molecular dynamic simulations

The spread of acquired immune deficiency syndrome has increasingly become a great concern owing largely to the failure of chemotherapies. The G48V is considered the key signature residue mutation of HIV-1 protease developing with saquinavir therapy. Molecular dynamics simulations of the wild-type and the G48V HIV-1 protease complexed with saquinavir were carried out to explore structure and interactions of the drug resistance. The molecular dynamics results combined with the quantum-based and molecular mechanics Poisson-Boltzmann surface area calculations indicated a monoprotonation took place on D25, one of the triad active site residues. The inhibitor binding of the triad residues and its interaction energy in the mutant were similar to those in the wild-type. The overall structure of both complexes is almost identical. However, the steric conflict of the substituted valine results in the conformational change of the P2 subsite and the disruption of hydrogen bonding between the -NH of the P2 subsite and the backbone -CO of the mutated residue. The magnitude of interaction energy changes was comparable to the experimental K(i) data. The designing for a new drug should consider a reduction of steric repulsion on P2 to enhance the activity toward this mutant strain.

Reversed-phase liquid chromatography with ultraviolet detection for simultaneous quantitation of indinavir and propranolol from ex-vivo rat intestinal permeability studies

A simple, rapid, sensitive and specific reversed-phase high performance liquid chromatographic (RP-HPLC) method involving ultraviolet detection (lambda = 210 nm) was developed for analysis of indinavir along with propranolol in samples obtained from ex vivo intestinal permeability studies. Chromatography was carried out on C-18 column with mobile phase comprising of phosphate buffer-acetonitrile (68:32, v/v) pumped at flow rate of 1 ml/min. The proposed method has a short run time of 12 min and involves a simple sample preparation for the purpose of reducing permeability model artifacts and to concentrate the samples. Fluorescein was used as internal standard. The proposed method has been validated with regard to specificity, detection limit, recovery, accuracy and precision. For both the drugs, method was found to be selective, linear (R(2) approximately 0.999), accurate (recovery = 100-105%) and precise (<3% R.S.D.) in the range of 2-20 microg/ml. The limit-of-detection and limit-of-quantification of the method were 40 ng/ml and 100 ng/ml for indinavir, and 30 and 80 ng/ml for propranolol, respectively. Indinavir, a widely prescribed HIV protease inhibitor, suffer from bioavailability problems where involvement of P-glycoprotein mediated drug efflux may play a significant role. The proposed method was successfully applied for intestinal permeability of indinavir to estimate the contribution of P-glycoprotein in limiting its oral bioavailability. The advantage of the developed method lies in the simultaneous determination of propranolol, a passive integrity marker, routinely employed in permeability studies and its selectivity in presence of various P-gp modulators and permeability markers.

Clinical pharmacology of antiretroviral therapy

Antiretroviral therapy represents by all means a new branch of anti-infective chemotherapy, and in order to describe the mode of action of antiretrovirals, a series of inferences from anti-bacterial chemotherapy were made. The currently available antiretroviral agents can be classified as time-dependent drugs, and therefore the key pharmacokinetic parameter adopted in their clinical-pharmacological assessment is the concentration at the end of the dosing interval (Ctrough). By focusing on this parameter, the application of Therapeutic Drug Monitoring (TDM) allows for the successful individual tailoring of the drug dosage in some clinical circumstances, such as treatment of drug-resistant infections, drug-drug interactions and side effects. While this procedure has now been sufficiently standardized for protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs), no clinical applications are yet recognized for nucleoside/nucleotide reverse transcriptase inhibitors (N/NtRTIs) and fusion inhibitors. The main unfavourable peculiarity of HIV infection, such as the need for lifelong treatment, is one of the reasons why increasing attention is being paid to pharmacological aspects of antiretroviral therapy. Issues like treatment potency, maintenance over time of the immunovirological benefit and long-term side effects require intensive pharmacological investigation in order to obtain the information on which basing the most convenient strategy to be adopted for the therapeutical management of this condition.

Capillary electrophoretic method for determination of protease inhibitor indinavir sulfate used in human immunodeficiency virus therapy

A simple, fast and reliable capillary electrophoresis (CE) method for determination of indinavir sulfate, a potent protease inhibitor used in human immunodeficiency virus (HIV) therapy, in commercial and simulated capsule formulations is described. The analysis was performed in a 75microm i.d. uncoated fused-silica capillary with 27cm length (effective length of 19.4cm) using a 20mmoll-1 phosphate buffer at pH 2.52. Samples were injected hydrodynamically by applying 0.5psi pressure during 2s. The applied voltage was 28kV. Direct UV detection at 214nm led to an adequate sensitivity without interference from sample excipients and known impurities. For quantitative purposes, diazepam was used as internal standard. Under optimized conditions, the migration times for indinavir sulfate and diazepam were 1.06 and 1.66min, respectively. Analytical curve of peak area ratios versus concentration in the range of 20.0-100.0microg/ml gave a coefficient of correlation of 0.9992, establishing the method linearity. The limits of detection and quantitation were 4.61 and 14.0microg/ml, respectively. The within-day precision expressed as relative standard deviation was <1.5% for 10 consecutive sample injections. An average recovery of 100.81+/-0.56% at three concentration levels was obtained. Based on the performance characteristics, the proposed methodology was found suitable for the determination of indinavir sulfate in capsule formulations, presenting additional advantages inherent to the CE technology, such as low consumption of reagents and column endurance.

Determination of protease inhibitors using liquid chromatography-tandem mass spectrometry

A method for the analysis of six protease inhibitors and one metabolite has been developed and validated. Amprenavir, ritonavir, saquinavir, lopinavir, indinavir, nelfinavir, and an active metabolite of nelfinavir (M8) are quantitated using reversed-phase liquid chromatography coupled to tandem mass spectrometry, equipped with an electrospray ionization source (ESI-LC-MS-MS). The validation data presented here shows that the method allows the rugged analysis of these species from one aliquot. The evolution of complex drug interactions assessments and the clinical use of therapeutic drug monitoring for these antiretrovirals will be a potential immediate application of this method.

Highly sensitive determination of saquinavir in biological samples using liquid chromatography-tandem mass spectrometry

A selective and sensitive method for the determination of the HIV protease inhibitor saquinavir in human plasma, saliva, and urine using liquid-liquid extraction and LC-MS-MS has been developed, validated, and applied to samples of a healthy individual. After extraction with ethyl acetate, sample extracts were chromatographed isocratically within 5 min on Kromasil RP-18. The drug was detected with tandem mass spectrometry in the selected reaction monitoring mode using an electrospray ion source and 2H(5)-saquinavir as internal standard. The limit of quantification was 0.05 ng/mL. The accuracy of the method varied between -1 and +10% (SD within-batch) and the precision ranged from +4 to +10% (SD batch-to-batch). The method is linear at least within 0.05 and 87.6 ng/mL. After a regular oral dose (600 mg) saquinavir concentrations were detectable for 48 h in plasma and were well correlated with saliva concentrations (r(2)=0.9348, mean saliva/plasma ratio 1:15.1). The method is well suited for low saquinavir concentrations in different matrices.

Quantitative determination of saquinavir from Caco-2 cell monolayers by HPLC-UV. High performance liquid chromatography

The validation and quantitative determination of the protease inhibitor, saquinavir, from confluent Caco-2 monolayers and from aqueous solution is reported. The high performance liquid chromatographic method consisted of an Ultramex 5 C(8) reverse-phase column (250 x 4.6 mm i.d.) and a mobile phase of acetonitrile:water:triethylamine (55:44:1, v/v/v, pH 6.5). Samples were analyzed using an ultraviolet detector at 238 nm, and diltiazem hydrochloride (66 micro g/mL) was used as an internal standard. A linear response over a broad concentration range (0.4-8.0 micro g/mL, r(2) = 0.997) was obtained. The limit of detection and quantitation was set at 0.14 and 0.4 micro g/mL, respectively. Over a 4 day period, the intra-day and inter-day precision ranged from 1 to 7% with a mean of 4%, and from 1 to 2% with a mean of 1.5%, respectively. Bench-top and storage stability of saquinavir was found to be satisfactory. The permeability of saquinavir through Caco-2 monolayers was estimated using this assay.

Relationship between levels of indinavir in hair and virologic response to highly active antiretroviral therapy

BACKGROUND

Suboptimal levels of antiretroviral drugs result in virologic failure in HIV-infected patients treated with highly active antiretroviral therapy (HAART).

OBJECTIVE

To assess the relationship between levels of indinavir in hair and virologic outcome.

DESIGN

Cross-sectional study.

SETTING

7 AIDS clinics in France.

PATIENTS

89 HIV-infected patients who received HAART that included indinavir.

MEASUREMENTS

Patients were classified as responders or nonresponders on the basis of viremia at the time of hair collection. In nonresponders, levels of indinavir in hair and resistance mutations in the protease gene were assessed at baseline and at the time of indinavir measurement.

RESULTS

Mean indinavir levels (+/-SD) were significantly higher in the 65 responders than in the 24 nonresponders (24.4 +/- 16 microg/g vs. 12.9 +/- 8.6 microg/g) (P < 0.001). Nonresponders with intermediate levels of indinavir in hair had more mutations in the protease gene than did nonresponders with low levels of indinavir in hair.

CONCLUSION

Indinavir levels in hair are associated with virologic outcome in patients receiving HAART.

Simultaneous determination of the six HIV protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) plus M8 nelfinavir metabolite and the nonnucleoside reverse transcription inhibitor efavirenz in human plasma by solid-phase extraction and column liquid chromatography

A sensitive and selective liquid chromatographic assay has been developed for the determination of the six currently protease inhibitors approved by the U.S. Food & Drug Administration (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) plus the M8 active metabolite of nelfinavir and the nonnucleoside reverse transcription inhibitor efavirenz in a single run. Pretreatment of 1-mL plasma sample spiked with internal standard was made by a solid-phase extraction procedure using a polymeric reversed-phase sorbent. Liquid chromatography was performed using a narrow-bore C18 reversed-phase column and gradient elution. Double ultraviolet detection at 265 nm (amprenavir) and at 210 nm (all other assayed drugs and internal standard) was used. Calibration curves were linear in the range 25 to 10,000 ng/mL, and the assay has been validated over the range 25 to 5,000 ng/mL. Average accuracies at four concentrations were in the range 92.4% to 103.0% and 94.4% to 103.0% for within-day and between-day, respectively, and the coefficients of variation were less than 8%. Mean absolute recoveries varied from 72.8% (ritonavir) to 93.7% (indinavir). No metabolite of the protease inhibitors was found to coelute with the drugs of interest or with the internal standard. At this time, among the tested drugs, especially all the currently licensed nucleosides and the other nonnucleoside reverse transcription inhibitor nevirapine that can be used in combination with the protease inhibitors, none was found to interfere with the assay.

Determination of amprenavir, a HIV-1 protease inhibitor, in human seminal plasma using high-performance liquid chromatography-tandem mass spectrometry

A HPLC-MS-MS method to measure amprenavir in human seminal plasma has been developed and validated. The procedure uses stable, isotopically labeled 13C6-amprenavir as an internal standard and 100 microl of sample. The method is accurate (bias less than or equal to 7.2%) and precise (within- and between-day RSDs less than or equal to 4.2%) over the dynamic range of 30-4,000 ng/ml. Recently, this simple and sensitive method was used to determine amprenavir concentrations in seminal samples collected from HIV-1 positive subjects receiving amprenavir antiretroviral therapy as part of a multicenter clinical trial.

Cell-based fluorescence assay for human immunodeficiency virus type 1 protease activity

The human immunodeficiency virus type 1 (HIV-1) protease is essential for production of infectious virus and is therefore a major target for the development of drugs against AIDS. Cellular proteins are also cleaved by the protease, which explains its cytotoxic activity and the consequent failure to establish convenient cell-based protease assays. We have exploited this toxicity to develop a new protease assay that relies on transient expression of an artificial protease precursor harboring the green fluorescent protein (GFP-PR). The precursor is activated in vivo by autocatalytic cleavage, resulting in rapid elimination of protease-expressing cells. Treatment with therapeutic doses of HIV-1 protease inhibitors results in a dose-dependent accumulation of the fluorescent precursor that can be easily detected and quantified by flow cytometric and fluorimetric assays. The precursor provides a convenient and noninfectious model for high-throughput screenings of substances that can interfere with the activity of the protease in living cells.

Simultaneous determination of the HIV protease inhibitors indinavir, amprenavir, saquinavir, ritonavir and nelfinavir in human plasma by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method for the simultaneous quantitative determination of five HIV protease inhibitors (i.e. indinavir, amprenavir, saquinavir, ritonavir and nelfinavir) in human plasma is described. An aliquot of 500 microl plasma was extracted with 0.5 ml of 0.1 M NH4OH and 5 ml of methyl tert.-butyl ether. After evaporating, the residue was dissolved in eluent mixture of acetonitrile and 50 mM KH2PO4 adjusted to pH 5.6 with 50 mM Na2HPO4 (43:57, v/v). Subsequently, the eluent was washed with hexane. Chromatography was performed using a C18 reversed-phase column. Ultraviolet detection at 215 nm was used. Linearity of the method was obtained in the concentration range of 0.05-20 microg ml(-1) for all five protease inhibitors. Our method is now in use to analyse plasma samples from patients treated with co-administration of HIV protease inhibitors.

The determination of a chlorinated benzofuran pharmaceutical intermediate by HPLC-MS with on-line derivatization

An HPLC-MS method for the analysis of 2-chloromethylbenzofuran, a pharmaceutical intermediate alkylating reagent employed in the preparation of a second generation HIV protease inhibitor, N-(2(R)-hydroxy-l(S)-indanyl)-2(R)-phenylmethyl-4(S)-hydroxy-5-(1-(4-(2- benzo[b]furanylmethyl)-2(S)-N'-9-t-butyl-carboxamido)-pipera zinyl))-pentaneamide, is described. Preliminary analysis of the protease inhibitor by HPLC-MS indicated that the quality of the drug substance was influenced by the composition of the chloromethylbenzofuran. Direct analysis of the chloromethylbenzofuran by LC-MS using atmospheric pressure ionization was unsuccessful, necessitating an alternative approach. The method described incorporated post-column derivatization of the chloromethyl benzofuran using a modification of the drug substance process chemistry yielding a derivative amenable to MS analysis using atmospheric pressure chemical ionization (APCI). This allowed measurement of an impurity in the chloromethylbenzofuran which was incorporated into the protease inhibitor.

Sensitive liquid chromatographic assay for amprenavir, a human immunodeficiency virus protease inhibitor, in human plasma, cerebrospinal fluid and semen

A sensitive bio-analytical assay for amprenavir, a human immunodeficiency virus protease inhibitor, based on reversed-phase liquid chromatography and fluorescence detection, is reported. The analyte is extracted from the matrix, plasma, cerebrospinal fluid (CSF) or semen, with chloroform using propyl-p-hydroxybenzoate as an internal standard. After centrifugation, evaporation of the organic phase and reconstitution in the eluent, the sample is injected into the chromatograph. The analyte is detected spectrofluorometrically at 270 and 340 nm for excitation and emission, respectively. The method has been validated in the 1-1000 ng/ml range for a 50-microl volume of plasma and in the 0.5-50 ng/ml range for a 100-microl volume of CSF and semen. The lower limit of quantification was 0.5 ng/ml in CSF and 1 ng/ml in both plasma and semen. Precision and accuracy both meet the current requirements for a bio-analytical assay and are <15% in the validated ranges. The assay was successfully used to obtain a concentration-time curve of amprenavir in plasma.

Acute tubulointerstitial nephritis attributable to indinavir therapy

Indinavir sulfate has been reported to cause asymptomatic crystalluria and nephrolithiasis in patients with human immunodeficiency virus (HIV) infection. Patients taking indinavir may present with asymptomatic crystalluria, nephrolithiasis with frank renal colic and obstruction, flank pain in the absence of nephrolithiasis, and dysuria or urgency. Asymptomatic crystalluria has been described as benign. Discontinuation of the drug has not been recommended in the absence of nephrolithiasis. We report two HIV-positive patients receiving indinavir who developed acute interstitial nephritis with foreign body giant cell reaction on renal biopsies. Both patients had asymptomatic crystalluria, although crystals were associated with clumps of white blood cells (WBCs) on urinalysis in one patient. Both cases show that the inflammatory response was significant enough to lead to tubular injury and acute renal impairment. Our findings suggest that asymptomatic crystalluria attributable to indinavir may illicit an inflammatory response with acute renal insufficiency, warranting monitoring of renal function, especially in patients with crystalluria.

Simultaneous determination of the HIV protease inhibitors indinavir, amprenavir, saquinavir, ritonavir, nelfinavir and the non-nucleoside reverse transcriptase inhibitor efavirenz by high-performance liquid chromatography after solid-phase extraction

As part of an on-going study on the suitability of a formal therapeutic drug monitoring (TDM) of antiviral drugs for improving the management of HIV infection, a high-performance liquid chromatography method has been developed to quantify simultaneously in plasma five HIV protease inhibitors (PIs) (i.e., indinavir, amprenavir, saquinavir, ritonavir, nelfinavir) and the novel non-nucleoside reverse transcriptase inhibitor efavirenz. After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl), with clozapine added as internal standard, is diluted 1:1 with phosphate buffer, pH 7 and subjected to a solid-phase extraction on a C18 cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H3PO4 neutralised with NaOH to pH 7. PIs and efavirenz are eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl 50% MeOH. A 40-microl volume is subjected to HPLC analysis onto a Nucleosil 100, 5 microm C18 AB column, using a gradient elution of MeCN and phosphate buffer adjusted to pH 5.15 and containing 0.02% sodium heptanesulfonate: 15:85 at 0 min-->30:70 at 2 min-->32:68 at 8 min-->42:58 at 18 min-->46:54 at 34 min, followed by column cleaning with MeCN-buffer, pH 5.15 (90:10), onto which 0.3% AcOH is added. Clozapine, indinavir, amprenavir, saquinavir, ritonavir, efavirenz and nelfinavir are detected by UV at 201 nm at a retention time of 8.2, 13.0, 16.3, 21.5, 26.5, 28.7 and 31.9 min, respectively. The total run time for a single analysis is 47 min, including the washing-out and reequilibration steps. The calibration curves are linear over the range 100-10,000 ng/ml. The absolute recovery of PIs/efavirenz is always higher than 88%. The method is precise with mean inter-day relative standard deviations within 2.5-9.8% and accurate (range of inter-day deviations -4.6 to +4.3%). The in vitro stability of plasma spiked with PIs/efavirenz at 750, 3000 and 9000 ng/ml has been studied at room temperature, -20 degrees C and +60 degrees C. The method has been validated and is currently applied to the monitoring of PIs and efavirenz in HIV patients. This HPLC assay may help clinicians confronted to questionable compliance, side effects or treatment failure in elucidating whether patients are exposed to adequate circulating drug levels. The availability of such an assay represents an essential step in elucidating the utility of a formal TDM for the optimal follow-up of HIV patients.

LC determination of indinavir in biological matrices with electrochemical detection

A high performance liquid chromatographic (HPLC) method with electrochemical detection for the quantification of Indinavir in cell culture is described. The sample pre-treatment involved a protein precipitation procedure using acetonitrile. Chromatography was carried out on a base-deactivated reversed-phase column with an isocratic mobile phase. The method was validated with regard to specificity, linearity, limits of detection and quantitation, precision and accuracy, recovery and ruggedness. The proposed HPLC assay was utilised to directly evaluate the capability of P-glycoprotein expressing multidrug resistant cells in mediating the transport and efflux of protease inhibitor (PI) Indinavir, a basic compound in AIDS care.

[Drug-induced urinary calculi in 1999]

Drug-induced urolithiasis are observed in 1.6% of the urinary calculi in France. Drugs crystals are identified in two thirds of these stones. Other drugs are responsible for stones which have an apparent metabolic origin (one third of the cases). Stone analysis using physical methods such as infrared spectroscopy is needed to unambiguously identify stones containing drugs. The inquiry is an important step to identify lithogenetic drugs which do not crystallize in the stones. The main substances which were identified in stones over the past decade were indinavir monohydrate (31.4%), triamterene (11.1%), sulphonamides (10.5%) and amorphous silica (4.5%). The main drugs involved in the nucleation and growth of metabolic stones were calcium and vitamin D supplementation (15%) and long-term treatment with carbonic anhydrase inhibitors (8%). Stone prevention is based on drug withdrawal or change in dosage with additional measures including an increase of diuresis and, if necessary, changes in the urine pH.

Determination of L-756 423, a novel HIV protease inhibitor, in human plasma and urine using high-performance liquid chromatography with fluorescence detection

A method for the determination of L-756 423, a novel HIV protease inhibitor, in human plasma and urine is described. Plasma and urine samples were extracted using 3M Empore extraction disk cartridges in the C18 and MPC (mixed-phase cation-exchange) formats, respectively. The extract was analyzed using HPLC with fluorescence detection (ex 248 nm, em 300 nm), and included a column switching procedure to reduce run-time. The assay was linear in the concentration range 5 to 1000 ng/ml when 1-ml aliquots of plasma and urine were extracted. Recoveries of L-756 423 were greater than 84% over the calibration curve range using the described sample preparation procedures. Intra-day precision and accuracy for this assay was less than 9% RSD and within 7%, respectively. Inter-day variabilities for the plasma (n=17) and urine (n= 10) were less than 5% and 3% for low (15 ng/ml) and high (750 ng/ml) quality control samples. Bovine serum albumin (0.5%) was used as an additive to urine to prevent precipitation of L-756 423 during the storage of clinical samples. The assay was used in support of human clinical trials.

[Nephritic colic due to indinavir]

OBJECTIVE

Evaluate the frequency and assess curative and preventive measures against urinary lithiasis in patients treated with indinavir.

PATIENTS AND METHODS

Fourteen HIV seropositive patients who developed severe and acute flank pain were included. Four of the patients receiving 800 mg indinavir t.i.d. had fever (38.5 degrees C) or delayed secretion (> 2 h). Delay from indinavir treatment onset was 1 to 321 days. During the same period, 155 patients had been treated with indinavir. Clinical features, radiology and laboratory results were recorded in addition to an analysis of the lithiasis if possible.

RESULTS

Transient moderate renal failure occurred in 8 patients. Mean urine pH was 6. Serum phosphorus, calcium, and uric acid, liver tests and urinalysis were normal. A JJ ureteral stent was inserted in 4 cases due to complications. In all cases, fluids, analgesics and antispasmodics provided favorable outcome. Inversely, nonsteroid antiinflammatory drugs given in 2 patients had a deleterious effect on renal function. The lithiasis was eliminated in 3 cases and infrared spectrophotometry demonstrated a structure compatible with indinavir monohydrate.

CONCLUSION

The formation of urinary lithiasis is a frequent complication of indinavir therapy (9%). Hyperhydration and urine acidification are usually successful but emergency drainage is required in approximately 3% of cases. Nonsteroidal antiinflammatory drugs should be avoided due to the risk of renal toxicity. A precise evaluation of fluid intake and diet, drug associations and personal history is needed to recognize patients at risk of recurrent lithiasis formation.

High-performance liquid chromatographic determination of ritonavir in human plasma, cerebrospinal fluid and saliva

A simple, ion-pair high-performance liquid chromatographic method has been developed and validated for the quantitative determination of the HIV protease inhibitor ritonavir in human plasma, cerebrospinal fluid and saliva. Sample pretreatment consisted of precipitation of proteins with acetonitrile prior to high-performance liquid chromatography with ultraviolet detection at 239 nm. The method has been validated over the range of 50 ng/ml to 50 microg/ml with use of 100-microl volumes of sample. The currently described assay has been used successfully for the analysis of ritonavir in plasma, cerebrospinal fluid and saliva in HIV-1 infected patients.

Identification of drug metabolites in biological matrices by intelligent automated liquid chromatography/tandem mass spectrometry

A rapid and systematic strategy for the identification of drug metabolites in biological matrices based on liquid chromatography-tandem mass spectrometry (LC/MS/MS) techniques was utilized for the identification of drug metabolites of the HIV protease inhibitor Indinavir. This strategy integrates intelligent realtime mass spectrometry with HPLC detection and a predictive strategy for detecting metabolites arising from common biotransformations, to rapidly elucidate structures of drug metabolites. Structures of metabolites generated from in vitro incubation mixtures of Indinavir were characterized from a single chromatographic analysis using the automated LC/MS/MS methodology, thus reducing data acquisition time and improving efficiency.

Urolithiasis associated with the protease inhibitor indinavir

OBJECTIVES

To report the association between the protease inhibitor indinavir and the development of urolithiasis.

METHODS

Case reports of three adult patients infected with the human immunodeficiency virus who developed surgical renal stones while being treated with indinavir are presented.

RESULTS

Of the 3 patients requiring surgical intervention, stone analyses were available in 2. One stone revealed an inner core of an unidentifiable crystal surrounded by calcium oxalate, and another was found to have indinavir components as determined by thin-layer chromatography and gas chromatography-mass spectrometry. Metabolic evaluation of all 3 patients identified significant hypocitraturia as an isolated finding.

CONCLUSIONS

The widely used protease inhibitor indinavir is associated with the development of urolithiasis and may act as a nidus for heterogeneous nucleation leading to the development of mixed urinary stones. Surgical intervention may be necessary in some cases. Underlying metabolic abnormalities may contribute to the increased incidence of stone formation. Urologists and other health care providers should be aware of this association, as combined medical and surgical intervention may be necessary.