A high-throughput, fully automated liquid/liquid extraction liquid chromatography/mass spectrometry method for the quantitation of a new investigational drug ABT-869 and its metabolite A-849529 in human plasma samples

Development of two fully automated quick, easy, cheap, effective, rugged, and safe pretreatment methods for the extraction of psychotropic drugs from whole blood samples

Quick, easy, cheap, effective, rugged, and safe extraction strategies are becoming increasingly adopted in various analytical fields to determine drugs in biological specimens. In the present study, we developed two fully automated quick, easy, cheap, effective, rugged, and safe extraction methods based on acetonitrile salting-out assisted liquid-liquid extraction (method 1) and acetonitrile salting-out assisted liquid-liquid extraction followed by dispersive solid-phase extraction (method 2) using a commercially available automated liquid-liquid extraction system. We applied these methods to the extraction of 14 psychotropic drugs (11 benzodiazepines and carbamazepine, quetiapine, and zolpidem) from whole blood samples. Both methods prior to liquid chromatography-tandem mass spectrometry analysis exhibited high linearity of calibration curves (correlation coefficients, > 0.9997), ppt level detection sensitivities, and satisfactory precisions (< 8.6% relative standard deviation), accuracies (within ± 16% relative error), and matrix effects (81-111%). Method 1 provided higher recovery rates (80-91%) than method 2 (72-86%), whereas method 2 provided higher detection sensitivities (limits of detection, 0.003-0.094 ng/mL) than method 1 (0.025-0.47 ng/mL) owing to the effectiveness of its dispersive solid-phase extraction cleanup step. These fully automated extraction methods realize reliable, labor-saving, user-friendly, and hygienic extraction of target analytes from whole blood samples.

Automation of the Whole-Blood Thiopurine S-Methyltransferase (TPMT) Phenotyping Assay Using the Biomek NXP and Biomek i5 Liquid-Handling Workstations

Assessment of thiopurine S-methyltransferase (TPMT) status is required before commencing thiopurine treatment to reduce the potential for adverse drug reactions. Our laboratory has provided a national TPMT phenotyping service since 2003. Our assay uses 6-thioguanine as substrate and detection of 6-methylthioguanine via high-performance liquid chromatography (HPLC) fluorescence. Here, we report the automation of this complex, labor-intensive, manual assay using the Biomek NX^P and Biomek i5 liquid-handling workstations. We optimized assay performance and validated for precision, linearity, and lower limit of quantitation. We also compared results from the manual and automated methods. Primary sample mixing and aliquoting were performed on the Biomek NX^P. On-board inversions (n = 10) replaced offline mixing. No carryover was observed. Eleven percent of primary sample tubes were incompatible with the Biomek NX^P, and these were assayed manually. The Biomek i5 was used to automate the enzyme assay. Optimum vortex mixing was achieved at 2500 rpm for 60 s, and the temperature was set to 37.0 °C for the 60 min enzyme incubation. Intra- and inter-assay precision were excellent, with coefficients of variation (CVs) of ≤2.3% and ≤7.4%, respectively, for patient samples. Linearity was demonstrated up to 199 mIU/L (R² = 0.992), with a lower limit of quantitation of 3.9 mIU/L. Correlation between the manual and automated methods was good (R² = 0.979, n = 405), with results being interchangeable. We have successfully developed and validated a novel automated method for the TPMT phenotyping enzyme assay. The two methods are cost-neutral. Automation of other complex enzyme assays may be possible using this approach.

Charge-Transfer Complex of Linifanib with 2,3-dichloro-3,5-dicyano-1,4-benzoquinone: Synthesis, Spectroscopic Characterization, Computational Molecular Modelling and Application in the Development of Novel 96-microwell Spectrophotometric Assay

Background

Linifanib (LFB) is a multi-targeted receptor tyrosine kinase inhibitor used in the treatment of hepatocellular carcinoma and other types of cancer. The charge-transfer (CT) interaction of LFB is important in studying its receptor binding mechanisms and useful in the development of a reliable CT-based spectrophotometric assay for LFB in its pharmaceutical formulation to assure its therapeutic benefits.

Purpose

The aim of this study was to investigate the CT reaction of LFB with 2,3-dichloro-3,5-dicyano-1,4-benzoquinone (DDQ) and its application in the development of a novel 96-microwell spectrophotometric assay for LFB.

Methods

The reaction was investigated, its conditions were optimized, the physicochemical and constants of the CT complex and stoichiometric ratio of the complex were determined. The solid-state LFB-DDQ complex was synthesized and its structure was analyzed by UV-visible, FT-IR, and ¹H-NMR spectroscopic techniques, and also by the computational molecular modeling. The reaction was employed in the development of a novel 96-microwell spectrophotometric assay for LFB.

Results

The reaction resulted in the formation of a red-colored product, and the spectrophotometric investigations confirmed that the reaction had a CT nature. The molar absorptivity of the complex was linearly correlated with the dielectric constant and polarity index of the solvent; the correlation coefficients were 0.9526 and 0.9459, respectively. The stoichiometric ratio of LFB:DDQ was 1:2. The spectroscopic and computational data confirmed the sites of interaction on the LFB molecule, and accordingly, the reaction mechanism was postulated. The reaction was utilized in the development of the first 96-microwell spectrophotometric assay for LFB. The assay limits of detection and quantitation were 1.31 and 3.96 μg/well, respectively. The assay was successfully applied to the analysis of LFB in its bulk and tablets with high accuracy and precision.

Conclusion

The assay is simple, rapid, accurate, eco-friendly as it consumes low volumes of organic solvent, and has high analysis throughput.

Development of 96-microwell Plate Assay with Fluorescence Reader and HPLC Method with Fluorescence Detection for High-throughput Analysis of Linifanib in its Bulk and Dosage Forms

Background:

Linifanib (LFB) is a tyrosine kinase inhibitor with antineoplastic activity. The existing methods for the analysis of LFB in bulk and dosage forms do not meet the requirements of quality control (QC) analysis.

Objective:

The present study was devoted to the development of two methods with high throughputs for determination of LFB. These methods are 96-microwell plate assay with microplate fluorescence reader (MWP-FR) and high-performance liquid chromatography with fluorescence detection (HPLC-FD).

Methods:

The MWP-FR assay was carried out in white opaque 96-well assay plates and the native fluorescence signals of LFB were measured at 360 nm for excitation and 500 nm for emission. In the HPLC-FD, the chromatographic separation of LFB and quinine sulphate (QS) as internal standard (IS) was performed on µ-Bondapack CN HPLC column using a mobile phase consisting of acetonitrile:water (60:40, v/v) pumped at a flow rate of 1 ml/min in an isocratic mode. The fluorescence detector was set at 350 nm for excitation and 454 nm for emission.

Results:

The linear ranges of the MWP-FR and HPLC-FD were 1-12 µg/well and 10-500 ng/ml, respectively. The limits of detection were 0.85 µg/well and 8.24 ng/ml for MWP-FR and HPLC-FD, respectively. Both MWP-FR and HPLC-FL methods were successfully applied for the determination of LFB in both bulk and tablets.

Conclusion:

Both methods have high analytical throughputs, they are suitable for use in QC laboratories for analysis of large numbers of LFB samples, and are environmentally friendly as they consume low volumes of chemicals and solvents.

Micelle-enhanced direct spectrofluorimetric method for the determination of linifanib: Application to stability studies

A new simple stability-indicating spectrofluorimetric method has been developed and validated for the determination of the tyrosine kinase inhibitor, linifanib (LNF). The proposed method makes use of the native fluorescence characteristics of LNF in a micellar system. Compared with aqueous solutions, the fluorescence intensity of LNF was greatly enhanced upon the addition of Tween-80. The relative fluorescence intensity of LNF was measured in a diluting solvent composed of 2% Tween-80: phosphate buffer pH 8.0 (20: 80, v/v) using excitation and emission wavelengths of 290 and 450 nm, respectively. The proposed method was fully validated as per the ICH guidelines. The recorded fluorescence intensity of LNF was rectilinear over a concentration range of 0.3-2 μg/ml with a high correlation coefficient (r = 0.9990) and low limits of detection (0.091 μg/ml) and quantitation (0.275 μg/ml). The applicability of the method was extended to study the inherent stability of LNF under different stress degradation conditions including, alkaline, acidic, oxidative, photolytic and thermal degradation. Moreover, the method was utilized to study the kinetics of the alkaline and oxidative degradation of LNF. The pseudo-first order rate constants and half-lives were calculated.

Simple, sensitive and rapid determination of linifanib (ABT-869), a novel tyrosine kinase inhibitor in rat plasma by UHPLC-MS/MS

BACKGROUND

Linifanib (ABT-869) is an orally active receptor tyrosine kinase inhibitor, which simultaneously inhibits vascular endothelial and platelet derived growth factor receptor. The aim of the present study was to develop an UHPLC-MS/MS method for the quantification of linifanib in rat plasma to support the pharmacokinetic and toxicokinetic studies.

RESULTS

Linifanib was separated on Acquity UPLC BEH™ C18 column (50 × 2.1 mm, i.d. 1.7 μm) using acetonitrile-10 mM ammonium acetate (60:40, v/v) as an isocratic mobile phase at a flow rate of 0.3 mL/min with sunitinib as internal standard (IS). Detection was performed on tandem mass spectrometer using electrospray ionization source in positive mode by multiple reaction monitoring. The monitored transitions were set at m/z 376.05 > 250.97 for linifanib and m/z 399.12 >283.02 for IS, respectively. Both linifanib and IS were eluted at 0.68 and 0.44 min, respectively with a total run time of 2.0 min only. The calibration curve was found to be linear over the concentration range of 0.40-500 ng/mL. The intra- and inter-day precision value was ≤10.6% and the accuracy ranged from 90.9-108.9%. In addition, all the validation results were within general assay acceptability criteria according to guidelines of bio-analytical method validation.

CONCLUSION

A selective and sensitive UHPLC-MS/MS method was developed and validated for the determination of linifanib in rat plasma for the first time. The developed method is simple, sensitive and rapid in terms of chromatographic separation and sample preparation and was successfully applied in a pilot pharmacokinetic study in rats.

MARS: bringing the automation of small-molecule bioanalytical sample preparations to a new frontier

Background: In recent years, there has been a growing interest in automating small-molecule bioanalytical sample preparations specifically using the Hamilton MicroLab® STAR liquid-handling platform. In the most extensive work reported thus far, multiple small-molecule sample preparation assay types (protein precipitation extraction, SPE and liquid–liquid extraction) have been integrated into a suite that is composed of graphical user interfaces and Hamilton scripts. Using that suite, bioanalytical scientists have been able to automate various sample preparation methods to a great extent. However, there are still areas that could benefit from further automation, specifically, the full integration of analytical standard and QC sample preparation with study sample extraction in one continuous run, real-time 2D barcode scanning on the Hamilton deck and direct Laboratory Information Management System database connectivity. Results: We developed a new small-molecule sample-preparation automation system that improves in all of the aforementioned areas. Conclusion: The improved system presented herein further streamlines the bioanalytical workflow, simplifies batch run design, reduces analyst intervention and eliminates sample-handling error.

Quantitative analysis of PD 0332991 in mouse plasma using automated micro-sample processing and microbore liquid chromatography coupled with tandem mass spectrometry

In the oncology therapeutic area, the mouse is the primary animal model used for efficacy studies. Often with mouse pharmacokinetic (PK) and pharmacokinetic/pharmacodynamic (PK/PD) studies, less than 20 μL of total plasma sample volume is available for bioanalysis due to the small size of the animal and the need to split samples for other measurements such as biomarker analyses. The need to conduct automated "small volume" sample processing for quantitative bioanalysis has therefore increased. An automated fit for purpose protein precipitation (PPT) method using a Hamilton MicroLab Star (Reno, NV, USA) to support mouse PK and PK/PD studies for an oncology drug candidate PD 0332991, (a specific inhibitor of cyclin-dependent kinase 4 (CDK-4) currently in development) for processing "small volumes" was developed. The automated PPT method was achieved by extracting and processing 10 μL out of a minimum sample volume of 15 μL plasma utilizing the Hamilton MicroLab Star. A 96-conical shallow well plate by Agilent Technologies, Inc (Wilmington, DE, USA) was the labware of choice used in the automated Hamilton "small volume" method platform. Analyses of a 10 μL plasma aliquot from 15 μL of plasma study samples were conducted by both automated and manual PPT method. All plasma samples were quantitated using a Sciex API 4000 triple quadrupole mass spectrometer coupled with an Eksigent Express HT Ultra HPLC system. The chromatography was achieved using an Agilent microbore C(18) Extend, 1.0 × 50 mm, 3.5 μm column at a flow rate of 0.150 mL/min with a total run time of 1.8 min. Accuracy and precision of standard and QC concentration levels were within 90-107% and <14%, respectively. Calibration curves were linear over the dynamic range of 1.0-1000 ng/mL. PK studies for PD 0332991 were conducted in female C3H mice following intravenous administration at 1mg/kg and oral administration at 2mg/kg. PK values such as area under curve (AUC), volume of distribution (Vd), clearance (Cl), half life (T(1/2)) and bioavailability (F%) demonstrated less than 11% difference between the automated Hamilton and manual PPT methods. The results demonstrate that the automated Hamilton PPT method can accurately and precisely aliquot 10 μL of plasma from 15 μL or larger volume plasma samples. The fit for purpose Hamilton PPT method is suitable for routine analyses of plasma samples from micro-sampling PK and PK/PD samples to support discovery studies.

Automated sample preparation for regulated bioanalysis: an integrated multiple assay extraction platform using robotic liquid handling

Background: A novel approach for regulated bioanalytical sample preparation has been developed to combine multiple types of extraction techniques into one integrated and automated sample-preparation suite that pairs a graphical user interface with the Hamilton Microlab® STAR robotic liquid handler. Results: The multi-assay sample-preparation suite is composed of three bioanalytical extraction techniques: protein precipitation, solid-phase extraction and liquid–liquid extraction. Validation data provided highly reproducible and robust results for each respective automated extraction technique. Conclusion: The user-friendly graphical user interface and modular method design provide a flexible and versatile approach for routine bioanalytical sample-preparation and is the first fully integrated multiple assay sample-preparation suite for regulated bioanalysis.

Simultaneous determination of a hydrophobic drug candidate and its metabolite in human plasma with salting-out assisted liquid/liquid extraction using a mass spectrometry friendly salt

In previously reported applications of salting-out assisted liquid/liquid extraction (SALLE) with acetonitrile, only inorganic salts were evaluated and implemented as the salting-out reagents. A potential concern of the method for the subsequent LC-MS analysis of biological samples was that a portion of the added salt (typically of high concentration) might be extracted and affect the chromatography separation and ionization of chromatography effluents in a mass spectrometer. Here we report, for the first time, the use of a mass spectrometry friendly organic salt, ammonium acetate, as a salting-out reagent in SALLE with acetonitrile for the simultaneous quantitation of an Abbott investigational new drug ABT-869 and its hydrophilic metabolite in human plasma. The performance of SALLE with ammonium acetate was compared with that of a previously reported method with a conventional liquid/liquid extraction technique using a set of pooled incurred samples. The % differences of the measured concentrations for 24 samples from these two methods were found to be within acceptance criteria, demonstrating SALLE with ammonium acetate as a reliable sample preparation technique. The SALLE method is simple, fast (25 min/plate), easy for automation, free of drying down step, and environmentally friendly. SALLE with mass spectrometry friendly salts has been applied to regulated sample analysis of both hydrophilic and hydrophobic compounds. It is envisioned that SALLE with acetonitrile and ammonium acetate be a universal method for high throughput automated sample preparation for bioanalytical chemistry.

High-performance liquid chromatography-tandem mass spectrometry in the identification and determination of phase I and phase II drug metabolites

Applications of tandem mass spectrometry (MS/MS) techniques coupled with high-performance liquid chromatography (HPLC) in the identification and determination of phase I and phase II drug metabolites are reviewed with an emphasis on recent papers published predominantly within the last 6 years (2002–2007) reporting the employment of atmospheric pressure ionization techniques as the most promising approach for a sensitive detection, positive identification and quantitation of metabolites in complex biological matrices. This review is devoted to in vitro and in vivo drug biotransformation in humans and animals. The first step preceding an HPLC-MS bioanalysis consists in the choice of suitable sample preparation procedures (biomatrix sampling, homogenization, internal standard addition, deproteination, centrifugation, extraction). The subsequent step is the right optimization of chromatographic conditions providing the required separation selectivity, analysis time and also good compatibility with the MS detection. This is usually not accessible without the employment of the parent drug and synthesized or isolated chemical standards of expected phase I and sometimes also phase II metabolites. The incorporation of additional detectors (photodiode-array UV, fluorescence, polarimetric and others) between the HPLC and MS instruments can result in valuable analytical information supplementing MS results. The relation among the structural changes caused by metabolic reactions and corresponding shifts in the retention behavior in reversed-phase systems is discussed as supporting information for identification of the metabolite. The first and basic step in the interpretation of mass spectra is always the molecular weight (MW) determination based on the presence of protonated molecules [M+H]⁺ and sometimes adducts with ammonium or alkali-metal ions, observed in the positive-ion full-scan mass spectra. The MW determination can be confirmed by the [M-H]^- ion for metabolites providing a signal in negative-ion mass spectra. MS/MS is a worthy tool for further structural characterization because of the occurrence of characteristic fragment ions, either MSⁿ analysis for studying the fragmentation patterns using trap-based analyzers or high mass accuracy measurements for elemental composition determination using time of flight based or Fourier transform mass analyzers. The correlation between typical functional groups found in phase I and phase II drug metabolites and corresponding neutral losses is generalized and illustrated for selected examples. The choice of a suitable ionization technique and polarity mode in relation to the metabolite structure is discussed as well.

A high-throughput liquid chromatography/tandem mass spectrometry method for simultaneous quantification of a hydrophobic drug candidate and its hydrophilic metabolite in human urine with a fully automated liquid/liquid extraction

ABT-869 (A-741439) is an investigational new drug candidate under development by Abbott Laboratories. ABT-869 is hydrophobic, but is oxidized in the body to A-849529, a hydrophilic metabolite that includes both carboxyl and amino groups. Poor solubility of ABT-869 in aqueous matrix causes simultaneous analysis of both ABT-869 and its metabolite within the same extraction and injection to be extremely difficult in human urine. In this paper, a high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) method has been developed and validated for high-speed simultaneous quantitation of the hydrophobic ABT-869 and its hydrophilic metabolite, A-849529, in human urine. The deuterated internal standards, A-741439D(4) and A-849529D(4), were used in this method. The disparate properties of the two analytes were mediated by treating samples with acetonitrile, adjusting pH with an extraction buffer, and optimizing the extraction solvent and mobile phase composition. For a 100 microL urine sample volume, the lower limit of quantitation was approximately 1 ng/mL for both ABT-869 and A-849529. The calibration curve was linear from 1.09 to 595.13 ng/mL for ABT-869, and 1.10 to 600.48 ng/mL for A-849529 (r2 > 0.9975 for both ABT-869 and A-849529). Because the method employs simultaneous quantification, high throughput is achieved despite the presence of both a hydrophobic analyte and its hydrophilic metabolite in human urine.