Quantitative determination of paclitaxel in human plasma using semi-automated liquid-liquid extraction in conjunction with liquid chromatography/tandem mass spectrometry

Paradigm Shift in the Arena of Sample Preparation and Bioanalytical Approaches Involving Liquid Chromatography Mass Spectroscopic Technique

Sample preparation is a highly important and integral part of bioanalysis for cleaning up the complex biological matrices and thereby minimizing matrix effect. Matrix effect can jeopardize the precise quantification and adversely affect the reliability of liquid chromatography-mass spectrometry-based analytical results by alteration of analyte ionization. Matrix components result in suppression or enhancement of the intensity of analyte response. In spite of the high specificity and selectivity of tandem mass spectrometry, a relatively higher concentration of coeluted matrix elements present in biofluids may alter the efficiency of quantification of a bioanalytical method. Numerous literature reports different types of sample preparation techniques employed in bioanalysis. In this review, the strategies for selection of the appropriate sample clean-up technique in bioanalysis are discussed extensively. A paradigm shift in the arena of sample preparation and bioanalytical approaches involving the liquid chromatography-mass spectroscopic technique has been scrutinized. Current trends and possible future advancements in the field of biological sample extraction methods, including instrumental techniques are analyzed in detail.

A new high-performance liquid chromatography-tandem mass spectrometry method for the determination of paclitaxel and 6α-hydroxy-paclitaxel in human plasma: Development, validation and application in a clinical pharmacokinetic study

Paclitaxel belongs to the taxanes family and it is used, alone or in multidrug regimens, for the therapy of several solid tumours, such as breast-, lung-, head and neck-, and ovarian cancer. Standard dosing of chemotherapy does not take into account the many inter-patient differences that make drug exposure highly variable, thus leading to the insurgence of severe toxicity. This is particularly true for paclitaxel considering that a relationship between haematological toxicity and plasma exposure was found. Therefore, in order to treat patients with the correct dose of paclitaxel, improving the overall benefit–risk ratio, Therapeutic Drug Monitoring is necessary. In order to quantify paclitaxel and its main metabolite, 6α-hydroxy-paclitaxel, in patients’ plasma, we developed a new, sensitive and specific HPLC–MS/MS method applicable to all paclitaxel dosages used in clinical routine. The developed method used a small volume of plasma sample and is based on quick protein precipitation. The chromatographic separation of the analytes was achieved with a SunFire^™ C18 column (3.5 μM, 92 Å, 2,1 x 150 mm); the mobile phases were 0.1% formic acid/bidistilled water and 0.1% formic acid/acetonitrile. The electrospray ionization source worked in positive ion mode and the mass spectrometer operated in selected reaction monitoring mode. Our bioanalytical method was successfully validated according to the FDA-EMA guidelines on bioanalytical method validation. The calibration curves resulted linear (R² ≥0.9948) over the concentration ranges (1–10000 ng/mL for paclitaxel and 1–1000 ng/mL for 6α-hydroxy-paclitaxel) and were characterized by a good accuracy and precision. The intra- and inter-day precision and accuracy were determined on three quality control concentrations for paclitaxel and 6α-hydroxy-paclitaxel and resulted respectively <9.9% and within 91.1–114.8%. In addition, to further verify the assay reproducibility, we tested this method by re-analysing the incurred samples. This bioanalytical method was employed with success to a genotype-guided phase Ib study of weekly paclitaxel in ovarian cancer patients treated with a wide range of drug’s dosages.

Characteristics, Properties and Analytical Methods of Paclitaxel: A Review

Paclitaxel is a diterpenoid pseudoalkaloid, isolated from Taxus brevifolia, and is largely used as an antitumoral drug. The formulation of paclitaxel known as Taxol® employs a mixture of Cremophor EL and dehydrated ethanol, due the low drug water solubility. However, Taxol® causes some unwanted side effects due to the presence of Cremophor EL and ethanol in the formulation. Based on this, there is a need for the development of drug delivery systems to enhance the solubility, permeability and stability of paclitaxel and to promote a controlled and targeted delivery for better therapeutic effect and reduced side effects. In addition, the drug has been qualitatively and quantitatively analyzed in different delivery systems. In this context, several approaches were reported focusing on the optimization of analytical methods and development of new ones, considering the need of a fast, simple, with enough sensibility and selectivity assay, which can be a problem in some analysis. This review presents a summary of methods used in quantification of paclitaxel in different matrices, such as plasma, urine, plant extract, cells and delivery systems.

Simultaneous quantitative analysis of polyethylene glycol (PEG), PEGylated paclitaxel and paclitaxel in rats by MS/MSALL technique with hybrid quadrupole time-of-flight mass spectrometry

PEGylation is practically one of most important modifications of drugs including small molecules, peptides and proteins, which has been proven to dramatically improve physicochemical properties and pharmacokinetic behavior of the PEGylated drugs. However, it is a challenge currently to quantitatively analyze PEG and PEGylated drugs by various analytical methods, even mass spectrometry because of multiple parent ion distribution of PEG caused by its polydispersity of molecular weight. Here we developed a robust method with MS/MS^ALL technique using electrospray ionization (ESI) source coupled high resolution Quadrupole Time-of-Flight (Q-TOF) mass spectrometry for the quantification of PEG2K-Paclitaxel (PEG-PTX) and its two metabolites, PEG and Paclitaxel (PTX). The analysis was performed on a 300SB-C18 column with acetonitrile and 0.1% formic acid as the mobile phase. Samples were simply prepared by protein precipitation in a small quantity of plasma (50μL). Calibration curve was linear within the range of 50.0-4000ng/mL for PEG and PEG-PTX and 1.0-1000ng/mL for PTX. The intra- and inter-day precisions were 3.2-6.9% and 3.1-6.9% for PEG, 4.1-7.8% and 4.0-9.9% for PEG-PTX, and 3.3-4.8% and 3.1-6.9% for PTX, respectively. The recoveries were greater than 90% with low matrix effects. Afterwards, the newly developed method was successfully applied to support a preclinical pharmacokinetic study in six rats after single intravenous injection of PEG-PTX (51.7mg/kg).

Mass spectrometry in the pharmacokinetic studies of anticancer natural products

In the history of medicine, nature has represented the main source of medical products. Indeed, the therapeutic use of plants certainly goes back to the Sumerian and Hippocrates and nowadays nature still represents the major source for new drugs discovery. Moreover, in the cancer treatment, drugs are either natural compounds or have been developed from naturally occurring parent compounds firstly isolated from plants and microbes from terrestrial and marine environment. A critical element of an anticancer drug is represented by its severe toxicities and, after administration, the drug concentrations have to remain in an appropriate range to be effective. Anyway, the drug dosage defined during the clinical studies could be inappropriate for an individual patient due to differences in drug absorption, metabolism and excretion. For this reason, personalized medicine, based on therapeutic drug monitoring (TDM), represents one of most important challenges in cancer therapy. Mass spectrometry sensitivity, specificity and fastness lead to elect this technique as the Golden Standard for pharmacokinetics and drug metabolism studies therefore for TDM. This review focuses on the mass spectrometry-based methods developed for pharmacokinetic quantification in human plasma of anticancer drugs derived from natural sources and already used in clinical practice. Particular emphasis was placed both on the pre-analytical and analytical steps, such as: sample preparation procedures, sample size required by the analysis and the limit of quantification of drugs and metabolites to give some insights on the clinical practice applicability. © 2015 Wiley Periodicals, Inc. Mass Spec Rev. 36:213-251, 2017.

Rapid and sensitive liquid chromatography coupled with electrospray ionization tandem mass spectrometry method for the analysis of paclitaxel, docetaxel, vinblastine, and vinorelbine in human plasma

BACKGROUND

A rapid and sensitive analytical method using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was developed for the determination of paclitaxel, docetaxel, vinblastine, and vinorelbine in human plasma.

METHODS

A simple liquid-liquid extraction procedure was applied using only 100-μL plasma. Chromatographic separation of these anticancer drugs was achieved with an isocratic mobile phase consisting of acetonitrile/aqueous buffer (10 mmol/L ammonium acetate and 0.1% formic acid in 70:30, vol/vol) at a flow rate of 0.25 mL/min in a short time (4.5 minutes).

RESULTS

The calibration curves for paclitaxel, docetaxel, vinblastine, and vinorelbine in spiked human plasma ranged from 25 to 2500, 10 to 1000, 10 to 1000, and 10 to 1000 ng/mL, respectively. The squares of the linear correlation coefficients were all more than 0.99. The intraday and interday relative standard deviations across 3 validation runs over the entire concentration range were less than 9.2%.

CONCLUSIONS

The established method should be helpful for the pharmacokinetic monitoring of paclitaxel, docetaxel, vinblastine, and vinorelbine in the human plasma of non-small cell lung cancer patients.

Quantification of taxanes in biological matrices: a review of bioanalytical assays and recommendations for development of new assays

Since the isolation of paclitaxel and its approval for the treatment of breast cancer, various taxanes and taxane formulations have been developed. To date, almost 100 bioanalytical assays have been published with the method development and optimization often extensively discussed by the authors. This Review presents an overview of assays published between January 1970 and September 2013 that described method development and validation of assays used to quantify taxanes in biological matrices such as plasma, urine, feces and tissue samples. For liquid chromatography assays, sample pretreatment, chromatographic separation and assay performance are compared. Since this Review discusses the limitations of previously developed liquid chromatography assays and gives recommendations for future assay development, it can be used as a reference for future development of liquid chromatography assays for the quantification of taxanes in various biological matrices to support preclinical and clinical studies.

Nonvascular drug-eluting stent coated with sodium caprate-incorporated polyurethane for the efficient penetration of paclitaxel into tumor tissue

To increase the therapeutic potency of nonvascular drug-eluting stents, sodium caprate was employed as a drug-penetration enhancer. A polytetrafluoroethylene-covered drug-eluting stent was coated with a mixture containing sodium caprate, paclitaxel, and polyurethane via the rolling coating technique. The coated stent has a smooth membrane surface with a 40-µm membrane thickness. Paclitaxel was released from the coated stent for two months. In the multilayered cell sheet model, sodium caprate in the polyurethane membrane (PUSC10) showed the possibility of enhancing the paclitaxel tissue penetration. The amount of penetrated paclitaxel for the sodium caprate-containing polyurethane membrane (PUSC10) was two times higher than that of sodium caprate-free polyurethane membrane. Additionally, the potential of sodium caprate was confirmed by a tumor-bearing small animal model. PUSC10 incorporated with Nile red (as a model fluorescence dye for visualization of drug penetration; PUSC10–Nile red) or PUSC10 incorporated with paclitaxel (PUSC10–paclitaxel) membrane was implanted at tumor sites in Balb/c mice. In the case of PUSC10–Nile red, the tissue penetration depth of Nile red was significantly increased from 30 µm (without sodium caprate) to 1060 µm (with sodium caprate). After seven days, an almost four times higher therapeutic area of PUSC10–paclitaxel was observed compared to that of polyurethane–paclitaxel (without sodium caprate) by a terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The results indicate that sodium caprate improves the penetration and therapeutic efficiencies of drugs in drug-eluting stents, and thus, it has potential for local stent therapy.

A rapid analytical method for the quantification of paclitaxel in rat plasma and brain tissue by high-performance liquid chromatography and tandem mass spectrometry

RATIONALE

Paclitaxel, an antitumor agent for the treatment of several types of cancers, has recently been reported to cause impaired cognitive function and neuropathic pain in humans. To assess the effects of paclitaxel on the central nervous system, a sensitive and accurate method is required to quantify paclitaxel concentrations in plasma and brain tissue obtained from rodents receiving paclitaxel.

METHODS

The biological samples were prepared by liquid-liquid extraction and separated by a 3.5 min reversed-phase liquid chromatography (RPLC) method using a BDS Hypersil C8 column under isocratic conditions. Paclitaxel was quantified using multiple reaction monitoring (MRM) with a triple quadrupole tandem mass spectrometer working in the positive electrospray ionization (ESI+) mode. A stable isotope labeled analogue of paclitaxel was used as the internal standard (IS).

RESULTS

The method was validated to be precise and accurate within the dynamic range of 0.5-100 ng/mL based on 100 μL plasma and 1.5-300 ng/g based on 33 mg of brain tissue in homogenate. This method was applied to samples from 2 mg/kg intravenously dosed rats. The plasma concentrations were observed to be 26.62 ± 8.93 ng/mL and brain concentrations 11.08 ± 4.18 ng/g when measured 4 h post-dose.

CONCLUSIONS

This rapid LC/MS/MS method was validated to be sensitive, specific, precise and accurate for the quantification of paclitaxel in rat plasma and brain tissue homogenate. Application of the method to study samples provided sufficient proof of blood-brain barrier penetration of paclitaxel, allowing further investigation of its influence on the central nervous system.

Quantitative determination of Lx2-32c, a novel taxane derivative, in rat plasma by liquid chromatography-tandem mass spectrometry

A sensitive and reliable LC-MS/MS method for the determination of Lx2-32c, a novel taxane derived from cephalomannine, has been developed and validated. Plasma samples containing Lx2-32c and paclitaxel (internal standard) were prepared based on a simple protein precipitation by the addition of two volumes of acetonitrile. The analyte and internal standard were separated on a Zorbax SB-C18 column (3.5μm, 2.1mm×100mm) with the mobile phase of acetonitrile/water containing 0.1% formic acid (v/v) with gradient elution at a flow rate of 0.2ml/min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) by multiple reactions monitoring (MRM) of the transitions at m/z 887.5→264.3 for Lx2-32c and 854.5→286.2 for IS. Linear detection responses were obtained for Lx2-32c ranging from 1 to 1000ng/ml. Inter- and intra-day precision (R.S.D.%) were all within 15% and the accuracy (R.E.%) was equal or lower than 8%. The lower limit of quantitation (LLOQ) was 1ng/ml and the average recovery was greater than 91.5%. The method was successfully applied to the pharmacokinetic study of Lx2-32c in rat plasma.

Development and application of a validated gradient elution HPLC method for simultaneous determination of 5-fluorouracil and paclitaxel in dissolution samples of 5-fluorouracil/paclitaxel-co-eluting stents

The combined use of 5-fluorouracil and paclitaxel is common in clinical trials. However, there are few methods for simultaneous determination of 5-fluorouracil and paclitaxel; most reported approaches can only quantitate either 5-fluorouracil or paclitaxel. This paper proposes a new gradient elution HPLC method for simultaneous determination of 5-fluorouracil and paclitaxel using a photodiode array detector, C₁₈ column (250 mm × 4.6 mm, 5 μm) with methanol and 0.5% H₃PO₄ aqueous solution as the mobile phase components. The injection volume was 50 μl and the column temperature was maintained at 30 °C. The method was validated according to USP Category I requirements. The validation characteristics included system suitability, linearity, analytical range, LOD, LOQ, accuracy, precision, specificity, stability, ruggedness and robustness. The calibration curves exhibited linear concentration ranges of 0.2-40 μg/ml for 5-fluorouracil and 1.5-150 μg/ml for paclitaxel with correlation coefficients larger than 0.99990. The lower limits of quantitation were 2 ng/ml for 5-fluorouracil and 0.75 μg/ml for paclitaxel, respectively. The intra and inter-day precision and accuracy were found to be well within acceptable limits (i.e., 5%). The results demonstrate that this method is reliable, reproducible and suitable for simultaneous quantitation of the two drugs in the release media of 5-fluorouracil/paclitaxel-co-eluting stents.

Stereochemical differentiation of C-7 hydroxyltaxane isomers by electrospray ionization mass spectrometry

In this study, different electrospray ionization mass spectrometric (ESI-MS) methods were utilized to analyze several pairs of taxane stereoisomers including paclitaxel and 7-epi-paclitaxel. Both ESI-MS and tandem mass spectrometry (MS/MS) techniques provided stereochemically dependent mass spectra in negative-ion mode, and all studied stereoisomers could be easily distinguished based on their characteristic ions or distinct fragmentation patterns. MS/MS experiments for several taxane analogues at various collision energies were performed to elucidate potential dissociation pathways. The gas-phase deprotonation potentials were also calculated to estimate the most thermodynamically favorable deprotonation site using DFT B3LYP/6-31G(d). The results of the theoretical studies agreed well with the fragmentation patterns of paclitaxel and 7-epi-paclitaxel observed from MS/MS experiments. In addition, it was found that liquid chromatography (LC)/ESI-MS was a useful and sensitive technique for assignment of C-7 taxane stereoisomers from realistic samples.

Profiling of yew hair roots from various species using ultra-performance liquid chromatography/electrospray ionization mass spectrometry

An efficient and sensitive profiling approach to complex yew samples was developed using ultra-performance liquid chromatography/electrospray ionization mass spectrometry (UPLC/ESI-MS). The UPLC-based method displayed short analytical time and improved peak capability, as well as high sensitivity. The appropriate in-source collision-induced dissociation (CID) energy was employed to produce informative characteristic ions which could be used for stereochemical and sub-structural assignment of yew constituents. The method was successfully applied in the rapid screening of yew hair roots from various species, and 53 constituents including 47 taxoids were detected from partially purified root extract. Notably, C-7 hydroxytaxane stereoisomers could be identified based on their different fragment ions under the optimal profiling conditions. It was also observed that hair roots from different Taxus species exhibited nearly identical chemical distribution, indicating they had similar metabolic frameworks. Additionally, Taxus root resources also display benign medicinal perspective because they have relatively simple chemical profiles and possess high yields of valuable taxanes such as paclitaxel, cephalomannine, 10-deacetylpaclitaxel and 7-xylosyltaxanes.

Recent developments in extraction procedures relevant to analytical toxicology

Sample preparation is an important step in the development of an analytical method but is often regarded as time-consuming, laborious work. Optimum sample preparation leads to enhanced selectivity and sensitivity, however, and reduces amounts of interfering matrix compounds, resulting in less signal suppression or enhancement. Recent developments in extraction techniques that could be of interest in clinical and forensic toxicology, for example liquid-liquid, solid-phase, and headspace extraction, are summarized in this review. The advantages and disadvantages of several extraction techniques are discussed, to enable the reader to choose an appropriate method of extraction for his or her application. Attention is paid to current trends in analytical toxicology, for example miniaturization, high throughput, and automation.

Liquid–liquid extraction of strongly protein bound BMS-299897 from human plasma and cerebrospinal fluid, followed by high-performance liquid chromatography/tandem mass spectrometry

BMS-299897 is a gamma-secretase inhibitor that is being developed for the treatment of Alzheimer's disease. Liquid-liquid extraction (LLE), chromatographic/tandem mass spectrometry (LC/MS/MS) methods have been developed and validated for the quantitation of BMS-299897 in human plasma and cerebrospinal fluid (CSF). Both methods utilized (13)C6-BMS-299897, the stable label isotope analog, as the internal standard. For the human plasma extraction method, two incubation steps were required after the addition of 5 mM ammonium acetate and the internal standard in acetonitrile to release the analyte bound to proteins prior to LLE with toluene. For the human CSF extraction method, after the addition of 0.5 N HCl and the internal standard, CSF samples were extracted with toluene and no incubation was required. The organic layers obtained from both extraction methods were removed and evaporated to dryness. The residues were reconstituted and injected into the LC/MS/MS system. Chromatographic separation was achieved isocratically on a MetaChem C18 Hypersil BDS column (2.0 mm x 50 mm, 3 microm). The mobile phase contained 10 mM ammonium acetate pH 5 and acetonitrile. Detection was by negative ion electrospray tandem mass spectrometry. The standard curves ranged from 1 to 1000 ng/ml for human plasma and 0.25-100 ng/ml for human CSF. Both standard curves were fitted to a 1/x weighted quadratic regression model. For both methods, the intra-assay precision was within 8.2% CV, the inter-assay precision was within 5.4% CV, and assay accuracy was within +/-7.4% of the nominal values. The validation and sample analysis results demonstrated that both methods had acceptable precision and accuracy across the calibration ranges.

The effect of alkylamine additives on the sensitivity of detection for paclitaxel and docetaxel and analysis in plasma of paclitaxel by liquid chromatography–tandem mass spectrometry

The formation of multiple molecular ions, especially due to sodium adduct ion formation, is commonly observed in electrospray mass spectrometry and may make reproducible and sensitive quantitation difficult. The objective of this work was to investigate the underlying mechanism involved in the suppression of multiple molecular ion formation and to improve the sensitivity of detection for the two anti-neoplastic agents paclitaxel and docetaxel. The results showed that alkylamine additives could significantly improve the detection of paclitaxel and docetaxel by suppression of multiple molecular ions through preferential formation of a predominant alkylamine adduct ion. Possible binding sites, binding interactions and binding competition were investigated for the sodium adduct and alkylamine adduct ions using various experimental techniques. The formation of a predominant amine adduct ion may be due to increased surface activity in the droplet. The optimal alkylamine for both analytes was octylamine, which increased peak heights of paclitaxel and docetaxel 4.8 and 3.7-fold (n = 3), respectively. The precision of the signals for the analytes was also improved 5.7-fold. A quantitative assay in plasma for paclitaxel was partially validated for the calibration range 1.0-1000 ng/mL (r = 0.9977) when using 0.05% octylamine as a reconstitution solution additive. The limit of detection (LOD) and limit of quantitation (LOQ) were 0.5 and 0.9 ng/mL, respectively. Acceptable precision, accuracy, specificity and sample stability were demonstrated for this assay. This approach may prove useful for other analytes with similar binding sites.

Determination of paclitaxel in human plasma following the administration of Genaxol or Genetaxyl by liquid chromatography/tandem mass spectrometry

A sensitive and specific assay for paclitaxel in plasma has been developed to overcome limitations in previously published assays, using liquid chromatography with tandem mass spectrometric detection. Plasma samples (100 microL) were subjected to liquid-liquid extraction with 1-chlorobutane/acetonitrile (4:1, v/v), with [(2)H(5)]paclitaxel employed as the internal standard. Chromatography was carried out with a Waters SymmetryShield C8 column (50 x 2.1 mm, 3.5 microm). The total run time, including equilibration, was 8 min, using a gradient of acetonitrile and 10 mM ammonium formate, pH 4.0. The assay is accurate and precise over the range of 2-2500 ng/mL and has been successfully applied to study the clinical pharmacokinetics of two formulations of paclitaxel, Genaxol and Genetaxyl, given orally and intravenously.

Measurement of paclitaxel and its metabolites in human plasma using liquid chromatography/ion trap mass spectrometry with a sonic spray ionization interface

A quantitative liquid chromatography/ion trap mass spectrometry method for the simultaneous determination of paclitaxel, 6alpha-hydroxypaclitaxel and p-3'-hydroxypaclitaxel in human plasma has been developed and validated. 6alpha-,p-3'-Dihydroxypaclitaxel was also quantified using paclitaxel as a reference and docetaxel as an internal standard. The substances were extracted from 0.500 mL plasma using solid-phase extraction. The elution was performed with acetonitrile and the samples were reconstituted in the mobile phase. Isocratic high-performance liquid chromatography analysis was performed by injecting 50 microL of reconstituted material onto a 100 x 3.00 mm C12 column with a methanol:1% trifluoroacetic acid/ammonium trifluoroacetate in H(2)O 70:30 mobile phase at 350 microL/min. The [M+H](+) ions generated in the sonic spray ionization interface were isolated and fragmented using two serial mass spectrometric methods: one for paclitaxel (transition 854 --> 569 & 551) and the dihydroxymetabolite (transition 886 --> 585 & 567) and one for the hydroxy metabolites (transition 870 --> 585 & 567; transition 870 --> 569 & 551) and docetaxel ([M+Na](+), transition 830 --> 550). Calibration curves were created ranging between 0.5 and 7500 ng/mL for paclitaxel, 0.5 and 750 ng/mL for 6alpha-hydroxypaclitaxel, and 0.5 and 400 ng/mL for p-3'-hydroxypaclitaxel. Adduct ion formation was noted and investigated during method development and controlled by mobile phase optimization. In conclusion, a sensitive method for simultaneous quantification of paclitaxel and its metabolites suitable for analysis in clinical studies was obtained.

Liquid chromatography/tandem triple-quadrupole mass spectrometry for determination of paclitaxel in rat tissues

A liquid chromatography/tandem triple-quadrupole mass spectrometry assay to quantify paclitaxel in rat tissue homogenates containing taxol or paclitaxel nanoliposome (PTX-NLP) was developed and validated. Liquid-liquid extraction with tert-butyl methyl ether was used for tissue sample preparation and docetaxel was used as the internal standard. Paclitaxel and docetaxel were separated on a 200 mm x 4.6 mm x 5 microm C(18) column and quantified using a triple-quadrupole mass spectrometer operating in positive ion electrospray selective reaction monitoring mode (ESI(+)-SRM) with a total run time of 6.0 min. The peak area of the m/z 876.3 --> 307.9 transition of paclitaxel is measured versus that of the m/z 830.3 --> 549.1 transition of docetaxel to generate the standard curves. The standard curves were linear over the concentration range of 0.2008-2008 ng/mL for different tissues. The method had high extraction recovery (>90%) and accuracy (>90%) with the intra-day and inter-day precision <15%. Frozen stability, freeze/thaw stability, extraction stability and solution stability at ambient temperature were examined, which indicated the tissue samples should be extracted within 5 days and avoid being frozen and thawed repeatedly over 5 times. Extracted samples after evaporation could be stored at -20 degrees C for 20 days without drug degradation and no degradation was also observed after solution samples were left to stand at ambient temperature for 24 h. This assay was used to support an in vivo biodistribution study of PTX-NLP in rats.

Development of a high-throughput method for the determination of itraconazole and its hydroxy metabolite in human plasma, employing automated liquid-liquid extraction based on 96-well format plates and LC/MS/MS

A semi-automated liquid chromatography-tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous quantification of the antifungal drug itraconazole (ITZ) and its coactive metabolite hydroxyitraconazole (OH-ITZ) in human plasma. The plasma samples underwent liquid-liquid extraction (LLE) in 2.2 mL 96 deepwell plates. ITZ, OH-ITZ and the internal standard (IS) R51012 were extracted from plasma, using a mixture of acetonitrile (ACN) and methyl t-butyl ether (MTBE) as the organic solvent. This specific mixture, due to its composition, had a significant impact on the performance of the assay. All liquid transfer steps, including preparation of calibration standards and quality control samples as well as the addition of the IS, were performed automatically using robotic liquid handling workstations for parallel sample processing. After vortexing, centrifugation and freezing, the supernatant organic solvent was evaporated. The analytes and IS were dissolved in a small volume of a reconstitution solution, an aliquot of which was analyzed by combined reversed phase LC/MS/MS, with positive ion electrospray ionization and a TurboIonSpray interface, using multiple reactions monitoring (MRM). The method was shown to be sensitive and specific to both ITZ and OH-ITZ, it revealed excellent linearity for the range of concentrations 2-500 ng mL(-1) for ITZ and 4-1000 ng mL(-1) for OH-ITZ, it was very accurate and it gave very good inter- and intra-day precisions. The proposed high-throughput method was employed in a bioequivalence study after per os administration of two 100 mg tablets of ITZ, and it allowed this study to be completed in under four days.

Liquid chromatography-mass spectrometry for the quantitative bioanalysis of anticancer drugs

The monitoring of anticancer drugs in biological fluids and tissues is important during both pre-clinical and clinical development and often in routine clinical use. Traditionally, liquid chromatography (LC) in combination with ultraviolet (UV), fluorescence, or electrochemical detection is employed for this purpose. The successful hyphenation of LC and mass spectrometry (MS), however, has dramatically changed this. MS detection provides better sensitivity and selectivity than UV detection and, in addition, is applicable to a significantly larger group of compounds than fluorescence or electrochemical detection. Therefore, LC-MS has now become the method of first choice for the quantitative bioanalysis of many anticancer agents. There are still, however, a lot of new developments to be expected in this area, such as the introduction of more sensitive and robust mass spectrometers, high-throughput analyses, and further optimization of the coupled LC systems. Many articles have appeared in this field in recent years and are reviewed here. We conclude that LC-MS is an extremely powerful tool for the quantitative analysis of anticancer drugs in biological samples.

Comparison of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) as inhibitors of cytochrome P450 2C8

Statins are involved in different types of drug interactions. Our objective was to study the effect of statins on cytochrome P450 (CYP) 2C8-mediated paclitaxel 6 alpha-hydroxylation by incubating paclitaxel and statins (0--100 microM) with pooled human liver microsomes. Simvastatin, lovastatin, atorvastatin and fluvastatin were the most potent inhibitors of CYP2C8 activity with K(i) (IC(50)) values of 7.1 (9.6) muM, 8.4 (15) microM, 16 (38) microM and 19 (37) microM, respectively. Cerivastatin, simvastatin acid and lovastatin acid were less potent inhibitors with K(i) (IC(50)) values ranging from 32 to 55 (30--67) microM. Rosuvastatin and pravastatin showed no appreciable effect on CYP2C8 activity even at 100 microM. In conclusion, all the statins tested, except rosuvastatin and pravastatin, had a significant inhibitory effect on the activity of CYP2C8 in vitro. Because many of the statins accumulate in the liver and because also their metabolites may inhibit CYP2C8 activity, in vivo studies are needed to investigate a possible interaction of simvastatin, lovastatin, atorvastatin and fluvastatin with CYP2C8 substrate drugs.

Development and validation of a liquid chromatography-tandem mass spectrometry assay for the quantification of docetaxel and paclitaxel in human plasma and oral fluid

A quantitative method for the simultaneous determination of docetaxel (Taxotere), paclitaxel (Taxol), 6alpha-hydroxypaclitaxel, and p-3'-hydroxypaclitaxel in human plasma and oral fluid is developed and validated. Oral fluid (this term is now preferred to saliva) was sampled with a Salivette collection device. The procedure used a simple liquid/liquid extraction with methyl tert-butyl ether followed by LC-ESI-MS/MS. Gradient elution was applied and provided increased robustness to ion suppression by the drug formulation vehicle (polysorbate 80 and Cremophor EL). Adduct ion formation with sodium and potassium was noticed and controlled by mobile-phase optimization. The protonated analytes generated in the positive ion mode were monitored through multiple reaction monitoring. Calibration was performed by internal standardization with cephalomannine, and regression curves were constructed ranging between 2 and 1000 ng/mL in plasma and 0.125 and 62.5 ng/mL in oral fluid, using a weighing factor of 1/x2. The regression curves were quadratic for paclitaxel and docetaxel and linear for the paclitaxel metabolites. Accuracy varied from 91.3 to 103.6%, and imprecision did not exceed 12.7% for all analytes in plasma and oral fluid. In conclusion, a sensitive and robust method was obtained, which fulfilled all validation criteria.

Fully automated liquid–liquid extraction for the determination of a novel insulin sensitizer in human plasma by heated nebulizer and turbo ionspray liquid chromatography-tandem mass spectrometry

I, 2-{[5,7-dipropyl-3-(trifluoromethyl)-1,2-benzisoxazol-6-yl]oxy}-2-methyl propionic acid is an alpha peroxisome proliferator-activated receptor (PPAR) agonist with some gamma activity being investigated for potential use in the treatment of Type II diabetes mellitus and dyslipidemia. Two automated liquid-liquid extraction methods were developed and validated for the determination of I in human plasma. Concentrations of I were determined over a wide range of clinical doses. For Method A, plasma was acidified and extracted with ethyl acetate using a fully automated procedure. Analysis was performed by LC-MS/MS with a turbo ionspray source in negative ion mode. For Method B, a larger volume of plasma was extracted and a heated nebulizer source was used on the mass spectrometer. Method A was linear from 0.05 to 50 ng/mL and Method B from 0.2 to 1000 ng/mL. Validation procedures showed that both methods were robust, specific and reproducible.

Paclitaxel quantification in mouse plasma and tissues containing liposome-entrapped paclitaxel by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetics study

A liquid chromatography-tandem mass spectrometry assay to quantify total paclitaxel in mouse plasma and tissue homogenates containing paclitaxel, Taxol, or liposome-entrapped paclitaxel-easy to use (LEP-ETU) was developed and validated. Docetaxel was used as the internal standard (IS). Liquid-liquid extraction with tert-butyl methyl ether was used for plasma sample preparation, and a one-step protein precipitation with acetonitrile containing 0.1% acetic acid was developed for tissue homogenates. Paclitaxel and IS are separated on a 50 x 2.1-mm C18 column and quantified using a triple-quadrupole mass spectrometer operating in positive ion electrospray multiple reaction monitoring mode, with a total run time of 3.5 min. The peak area of the m/z 854.4--> 286.2 transition of paclitaxel is measured versus that of the m/z 808.5--> 527.5 transition of IS to generate the standard curve. In plasma, the linear range is 0.2-500 ng/mL and could be extended by dilution to 100,000 ng/mL with acceptable precision and accuracy (< or = 15%). The lower limit of quantification is 0.5 ng/mL in tissue homogenates (10 ng/g tissue), and the standard curve is linear up to 1000 ng/mL, with precision and accuracy < or = 15%. This assay was used to support a pharmacokinetics and tissue distribution study of LEP-ETU in mice.

A simple and sensitive assay for the quantitative analysis of paclitaxel and metabolites in human plasma using liquid chromatography/tandem mass spectrometry

A sensitive and specific LC-MS/MS assay for the determination of paclitaxel and its 3'p- and 6-alpha-hydroxy metabolites is presented. A 200 microL plasma aliquot was spiked with a 13C6-labeled paclitaxel internal standard and extracted with 1.0 mL tert-butylmethylether. Dried extracts were reconstituted in 0.1 M ammonium acetate-acetonitrile (1:1, v/v) and 25 microL volumes were injected onto the HPLC system. Separation was performed on a 150 x 2.1 mm C18 column using an alkaline eluent (10 mm ammonium hydroxide-methanol, 30:70, v/v). Detection was performed by positive ion electrospray followed by tandem mass spectrometry. The assay quantifies a range for paclitaxel from 0.25 to 1000 ng/mL and metabolites from 0.25 to 100 ng/mL using 200 microL human plasma samples. Validation results demonstrate that paclitaxel and metabolite concentrations can be accurately and precisely quantified in human plasma. This assay is now used to support clinical pharmacologic studies with paclitaxel.

Pharmacokinetic measurements of IDN 5390 using electrospray ionization tandem mass spectrometry: structure characterization and quantification in dog plasma

In this report, electrospray ionization tandem mass spectrometry (ESI-MS/MS) for a pharmacokinetic study of IDN 5390, a novel C-seco taxane derivative, which is under preclinical evaluation, has been investigated. Our results showed that IDN 5390 and other taxanes including paclitaxel and IDN 5109 could ionize well in not only positive-, but also in negative-ion mode. Under collision-induced dissociation (CID) conditions, these compounds could fragment into similar M- (molecular), T- (taxane ring) and S- (side chain) series ions. In positive-ion ESI, the formation of both T- and S-series ions involved the breaking of the C-13 ester bond. In negative-ion ESI, however, while the formation mechanism of S-series ions remained the same, the breaking of the C-1' carboxylic ester bond resulted in T-series ions. At optimum collision energy (CE) values, M-, T- and S-series ions of IDN 5390 in both positive- and negative-ion ESI-MS/MS spectra had good intensity. This phenomenon makes both positive- and negative-ion ESI-MS/MS good methods for IDN 5390 metabolite structural characterization, i.e. to reveal the location of modification groups in IDN 5390 metabolites versus IDN 5390 either on the side chain or the taxane ring. A liquid chromatography (LC)/ESI-MS/MS method using the multiple-reaction monitoring (MRM) technique was thereafter developed to quantify IDN 5390 in dog plasma using paclitaxel as internal standard. The method was validated using a concentration range between 5 and 1000 ng/mL and had a limit of detection of 1 ng/mL. The inter-day %CV (%coefficient of variation) of the calibration standards ranged between 4.36 and 9.64%, the intra-day %CV of the calibration standards between 0.61 and 13.44%, and the mean % accuracy of the quality control samples at the low, middle and high end of the concentration curves were 12.5, 6.8 and 9.6%, respectively.

A simple and sensitive assay for the quantitative analysis of paclitaxel in human and mouse plasma and brain tumor tissue using coupled liquid chromatography and tandem mass spectrometry

The development and validation of an assay for the determination of paclitaxel in human plasma, human brain tumor tissue, mouse plasma and mouse brain tumor tissue is described. Paclitaxel was extracted from the matrices using liquid-liquid extraction with tert-butyl methyl ether, followed by chromatographic analysis using an alkaline eluent. Positive ionization electrospray tandem mass spectrometry was performed for selective and sensitive detection. The method was validated according to the FDA guidelines on bioanalytical method validation. Validation results indicate that calibration standards in human plasma can be used to quantify paclitaxel in all tested matrices. In human samples, the validated range for paclitaxel was from 0.25-1000 ng ml(-1) using 200 microl plasma aliquots and from 5 to 5000 ng g(-1) using 50 microl tumor homogenate aliquots (0.2 g tissue ml(-1) control human plasma). In mice, the ranges were 1-1000 ng ml(-1) and 5-5000 ng g(-1) using 50 microl of mouse plasma and 50 microl of tumor homogenate aliquots (0.2 g tissue ml(-1) control human plasma), respectively. The method can be applied to studies generating only small sample volumes (e.g. mouse plasma and tumor tissue), but also to studies in human plasma requiring a lower limit of quantitation. The assay was applied successfully to several studies with both human and mouse samples.