High-throughput chromatographic approaches to liquid chromatographic/tandem mass spectrometric bioanalysis to support drug discovery and development

Applications of chromatographic methods in metabolomics: A review

Chromatography is a robust and reliable separation method that can use various stationary phases to separate complex mixtures commonly seen in metabolomics. This review examines the types of chromatography and stationary phases that have been used in targeted or untargeted metabolomics with methods such as mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. General considerations for sample pretreatment and separations in metabolomics are considered, along with the various supports and separation formats for chromatography that have been used in such work. The types of liquid chromatography (LC) that have been most extensively used in metabolomics will be examined, such as reversed-phase liquid chromatography and hydrophilic liquid interaction chromatography. In addition, other forms of LC that have been used in more limited applications for metabolomics (e.g., ion-exchange, size-exclusion, and affinity methods) will be discussed to illustrate how these techniques may be utilized for new and future research in this field. Multidimensional LC methods are also discussed, as well as the use of gas chromatography and supercritical fluid chromatography in metabolomics. In addition, the roles of chromatography in NMR- vs. MS-based metabolomics are considered. Applications are given within the field of metabolomics for each type of chromatography, along with potential advantages or limitations of these separation methods.

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid-liquid, solid-phase and related techniques) applied to the biomatrix. In the review, chiral, isotope-labeling, hydrophobicity-tailored and post-column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).

Current status and future directions of high-throughput ADME screening in drug discovery

During the last decade high-throughput in vitro absorption, distribution, metabolism and excretion (HT-ADME) screening has become an essential part of any drug discovery effort of synthetic molecules. The conduct of HT-ADME screening has been "industrialized" due to the extensive development of software and automation tools in cell culture, assay incubation, sample analysis and data analysis. The HT-ADME assay portfolio continues to expand in emerging areas such as drug-transporter interactions, early soft spot identification, and ADME screening of peptide drug candidates. Additionally, thanks to the very large and high-quality HT-ADME data sets available in many biopharma companies, in silico prediction of ADME properties using machine learning has also gained much momentum in recent years. In this review, we discuss the current state-of-the-art practices in HT-ADME screening including assay portfolio, assay automation, sample analysis, data processing, and prediction model building. In addition, we also offer perspectives in future development of this exciting field.

A simple, effective approach for rapid development of high-throughput and reliable LC-MS/MS bioanalytical assays

BACKGROUND

Rapidly developing LC-MS/MS assays with high-throughput and quality are challenging yet desired. Methodology & results: A simple method development approach was reported and demonstrated with the quantitative bioanalysis of BMS-984478, a hepatitis C virus nonstructural protein 5A inhibitor. An accurate, precise and robust LC-MS/MS method for the quantitation of BMS-984478 in rat and monkey plasma was developed and validated. Incurred sample reanalysis evaluation passed with 100% of samples meeting the acceptance criteria. The validated assay was successfully applied in toxicology studies without any failed runs.

CONCLUSION

The approach was successfully applied to the bioanalysis of BMS-984478 in toxicology and clinical studies. This approach was shown to be effective and reliable in speeding the development of high-throughput and reliable LC-MS/MS assays.

Licit and illicit drugs in a wastewater treatment plant in Verona, Italy

The occurrence of 12 active substances among licit and illicit drugs was investigated over a 2 week period inflowing and outflowing in an activated sludge wastewater treatment plant in the city of Verona, Northern Italy. Chemical analyses were performed by means of on-line solid phase extraction coupled to high performance liquid chromatography-tandem mass spectrometry in order to minimize sample pre-treatment. Quantifiable concentrations, up to hundreds of ng/L, were detected in influent and in effluent only for carbamazepine, codeine and benzoylecgonine. Such values are in accordance with literature data, so as removal efficiencies: it was observed that there was pretty much no abatement for carbamazepine, while average removal percentages of about 60% and 90% were calculated for codeine and benzoylecgonine, respectively. These results provide useful information (also concerning some active principles never or rarely detected, up to now, such as lormetazepam) for integrated water cycle managing, also taking into account the specific characteristics of the receiving water basin.

High-speed gradient elution reversed-phase liquid chromatography of bases in buffered eluents. Part I. Retention repeatability and column re-equilibration

We studied the run-to-run repeatability of the retention times of both non-ionizable and basic compounds chromatographed using buffered eluents. The effect of flow rate, organic modifier and other additives, buffer type/concentration, stationary phase type, batch-to-batch preparation of the initial eluent, gradient time, sample type and intra-day changes on retention repeatability were examined. We also assessed the effect of column storage solvent conditions on the inter-day repeatability. Although retention repeatability is strongly influenced by many parameters (flow rate, solvent compressibility compensation, precision of temperature control, and buffer/stationary phase type), our primary finding is that with a reasonable size column (15cmx4.6mm (i.d.)) two column volumes of re-equilibration with initial eluent suffices to provide acceptable repeatability (no worse than 0.004min) for both non-ionizable and basic analytes under a wide variety of conditions. Under ideal conditions (e.g. the right buffer, flow rate, etc.) it is possible to obtain truly extraordinary repeatability often as good as 0.0004min. These absolute fluctuations in retention translate to worst case changes in resolution of 0.2 units and average changes of only 0.02 units.

Development of capillary electrochromatography with poly(styrene-divinylbenzene-vinylbenzenesulfonic acid) monolith as the stationary phase

A new polystyrene-based monolithic stationary phase, which was prepared by single step in situ copolymerization of styrene, divinylbenzene and vinylbenzenesulfonic acid (VBSA), was developed as a separation column for capillary electrochromatography, in which VBSA was employed as the charge-bearing monomer. Polymerization time of the polystyrene-based monolith had slightly influenced the separation time of the tested analytes, but it effectively altered their separation resolutions. Furthermore, baseline separation for a wider range of acetonitrile levels of mobile phase was achieved when a monolithic column prepared by a longer polymerization time was used. This novel polystyrene-based monolithic column provided an adequate electroosmotic flow either in basic or acidic mobile phase when VBSA level was maintained at 2.6% (w/w). Finally, this proposed polystyrene-based column allowed seven tested analytes to achieve a reproducible baseline separation within 2.2 min with theoretical plate numbers higher than 164 000 plates/m.

Two-dimensional reverse phase-reverse phase chromatography: A simple and robust platform for sensitive quantitative analysis of peptides by LC/MS. Hardware design

We have revised current two-dimensional RP-RP approaches and developed a new robust 2-D RP-RP platform. This platform was implemented on an Agilent 1100 2-D liquid chromatography system and is based on high pressure switching between two high-resolution RP columns. An independent binary gradient was implemented for each dimension. The powerful combination of dual analytical columns with independent gradient elution achieves high analyte purity, effectively eliminates matrix effects, and maximizes MS sensitivity in Q1 SIM comparable to the sensitivity enhancements of MS/MS-based methods. Implementation of dual simultaneous gradient profiles (overlapped gradients) reduces 2-D method run-time to the scale of 1-D method run-times. This robust and sensitive approach is particularly suitable for hydrophobic peptides and small proteins and can be used as a routine standard technique for enhanced on-line peptide purification coupled with mass spectrometric detection.

Partial within-animal calibration: A new calibration approach in lead optimisation high-throughput bioanalysis

The lead optimization phase of drug discovery requires high-throughput analyses for quantification in biological matrices and in plasma in particular. Over the last decade, some technical innovations allowed the pharmaceutical industry to improve the quality of the results. However, there is room for improvement. In this context, a new calibration strategy is proposed in this paper. Experiments were performed on dog plasma samples and it was showed that a within-animal calibration strategy can reduce the bias up to 20% and improve the precision up to 20%. However, a partial within-animal calibration is preferred to the full approach in order to avoid to many sample preparations.

Determination of ximelagatran, melagatran and two intermediary metabolites in plasma by mixed-mode solid phase extraction and LC–MS/MS

An analytical method was developed for the determination of ximelagatran, an oral direct thrombin inhibitor, its active metabolite melagatran, and the two intermediate metabolites, OH-melagatran and ethyl-melagatran in human plasma. Extraction of plasma was carried out on a mixed mode bonded sorbent material (C8/SO(3)(-)). All four analytes, including their isotope-labelled internal standards, were eluted at high ionic strength with a mixture of 50% methanol and 50% buffer (0.25 M ammonium acetate and 0.05 M formic acid, pH 5.3) with an extraction recovery above 80%. The extracts were demonstrated to be clean in terms of a low concentration of albumin and lysoPC. The sample extraction was fully automated and performed in 96-well plates using a Tecan Genesis pipetting robot. Analysis of the extracts were performed with liquid chromatography followed by positive electrospray ionization mass spectrometry. The low organic content and the low pH of the extracts allowed for, after dilution 1:3 with buffer, direct injection onto the LC-column. The four analytes were separated on a C18 analytical LC-column using gradient elution with the acetonitrile concentration varying from 10 to 30% (v/v) and the ammonium acetate and acetic acid concentration kept constant at 10 and 5 mmol/L, respectively, at a flow rate of 0.75 mL/min. Linearity was achieved over the calibrated range 0.010-4.0 micromol/L with accuracy and relative standard deviation in the range 96.9-101.2% and 6.6-17.1%, respectively at LLOQ, and in the range 94.7-102.6% and 2.7-6.8%, respectively at concentrations above 3 x LLOQ. The method replaces a manual method, and displays the advantages of having a fully automated sample clean-up, no evaporation/reconstitution step, high recovery, and complete LC-separation of all four analytes.

High-throughput screening for multi-class veterinary drug residues in animal muscle using liquid chromatography/tandem mass spectrometry with on-line solid-phase extraction

A rapid qualitative method using on-line column-switching liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for screening 13 target veterinary drugs: four macrolides - erythromycin A, josamycin (leucomycin A3), kitasamycin (leucomycin A5), and tylosin A; six (fluoro)quinolones - ciprofloxacin, danofloxacin, enrofloxacin, flumequine, oxolinic acid, and sarafloxacin; and lincomycin, virginiamycin M1, and trimethoprim in different animal muscles. Clindamycin, norfloxacin, nalidixic acid, oleandomycin, ormetoprim, and roxithromycin were used as the internal standards. After simple deproteination and analyte extraction of muscle samples using acetonitrile, the supernatant was subjected to on-line cleanup and direct analysis by LC/MS/MS. On-line cleanup with an extraction cartridge packed with hydrophilic-hydrophobic polymer sorbent followed by fast LC using a short C18 column resulted in a total analysis cycle of 6 min for 19 drugs. This screening method considerably reduced the time and the cost for the quantitative and confirmatory analyses. The application of a control point approach was also introduced and explained.

Moving from fast to ballistic gradient in liquid chromatography/tandem mass spectrometry pharmaceutical bioanalysis: Matrix effect and chromatographic evaluations

The paper describes the steps taken by the authors to move from a fast to a ballistic gradient in routine liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis of plasma samples from pharmacokinetic (PK) profiling of new chemical entities. The reduction of column dimensions from 50 x 4.6 mm to 30 x 2.1 mm followed by optimization of chromatographic separation led to a decrease in the typical runtime from 5 (fast) to 2 min (ballistic) using an API4000 tandem mass spectrometer in Turbo Ionspray mode for detection. Three analytical standards representing typical molecular structures from our sample repository were used to spike plasma from four different species (rat, dog, human and mouse). Two different approaches were used to evaluate matrix effect: post-column infusion and comparison of the peak areas of neat standards and standards spiked after extraction into different pools of plasma; the influence of PEG400 as a typical dosing vehicle was also considered. Two different protein precipitation procedures were taken into account for sample extraction prior to injection. Peak shape, width and height, selectivity and sensitivity of the method were taken into account for chromatographic evaluation. The ballistic method was successfully cross-validated with the conventional fast gradient chromatographic assay.

Liquid chromatography-mass spectrometry and related techniques for purity assessment in early drug discovery

The combination of HPLC and MS has become the most valuable analytical tool to determine the identity and purity of a drug substance in the drug discovery arena over the past decade. This article describes different LC/MS configurations and their broad applicability to meet the fundamental analytical requirements involved in discovering new drugs. In addition, the value of chemiluminescence nitrogen detection for absolute purity determination and the convenience of CE as an orthogonal separation technique to HPLC are also discussed. In summary, LC/MS-based methodologies that implicate automation, various levels of throughput and open access systems have proved to be an integral part of the drug discovery process. As a result, the paradigm of high-quality/-quantity information is fulfilled in a timely fashion.

Turbulent flow chromatography for the reduction of matrix effects in electrospray ionization mass spectrometry-based enzyme assays

Turbulent flow chromatography (TFC) is presented as a means to reduce ion suppression in simultaneous multianalyte mass spectrometric bioassays. In this study, the effects of enzymes present in the sample on the signal response of five analytes were simultaneously investigated over a protein content range from 0 to 38 microg/mL by means of direct flow injection MS. As model enzymes, trypsin, thrombin, and chymotrypsin were selected. Without employment of TFC, both signal suppression and signal enhancement, depending on the nature of the analyte and the amount of matrix in the sample, were observed. Generally, these matrix effects were found to be intolerably large. The deviation from the mean signal response as a measure of deterioration was found to be between 14 and 112%. The addition of an excess of methanol as means of sample clean-up was investigated and found not to be sufficient. By employing TFC for online sample preparation, it was possible to reduce the matrix effecTs to a minimum for all model systems investigated. In case of trypsin the distortion could be lowered from 41.9 to 2.6%. Thus, TFC is considered to be a highly valuable tool for improving the sensitivity and reliability in the monitoring of enzymatic conversions by means of MS.

Development and application of a new on-line SPE system combined with LC–MS/MS detection for high throughput direct analysis of pharmaceutical compounds in plasma

A technique using a fully automated on-line solid phase extraction (SPE) system (Symbiosis, Spark Holland) combined with liquid chromatography (LC)-mass spectrometry (MS/MS) has been investigated for fast bioanalytical method development, method validation and sample analysis using both conventional C18 and monolithic columns. Online SPE LC-MS/MS methods were developed in the automated mode for the quantification of model compounds (propranolol and diclofenac) directly in rat plasma. Accuracy and precision using online SPE LC-MS/MS with conventional C18 and monolithic columns were in the range of 88-111% and 0.5-14%, respectively. Total analysis cycle time of 4 min per sample was demonstrated using the C18 column. Monolithic column allowed for 2 min total cycle time without compromising the quality and validation criteria of the method. Direct plasma sample injection without on-line SPE resulted in poor accuracy and precision in the range of 41-108% and 3-81%. Furthermore, the increase in back pressure resulted in column damage after the injection of only 60 samples.

A novel on-line solid-phase extraction approach integrated with a monolithic column and tandem mass spectrometry for direct plasma analysis of multiple drugs and metabolites

An on-line solid-phase extraction liquid chromatography/tandem mass spectrometry (SPE LC/MS/MS) assay using a newly developed SPE column and a monolithic column was developed and validated for direct analysis of plasma samples containing multiple analytes. This assay was developed in an effort to increase bioanalysis throughput and reduce the complexity of on-line SPE LC/MS/MS systems. A simple column-switching configuration that requires only one six-port valve and one HPLC pumping system was employed for on-line plasma sample preparation and subsequent gradient chromatographic separation. The resulting analytical method couples the desired sensitivity with ease of use. The method was found to perform satisfactorily for direct plasma analysis with respect to assay linearity, specificity, sensitivity, precision, accuracy, carryover, and short-term stability of an eight-analyte mixture in plasma. A gradient LC condition was applied to separate the eight analytes that cannot be distinctly differentiated by MS/MS. With a run time for every injection of 2.8 min, a minimum of 300 direct plasma injections were made on one on-line SPE column without noticeable changes in system performance. Due to the ruggedness and simplicity of this system, generic methods can be easily developed and applied to analyze a wide variety of compounds in a high-throughput manner without laborious off-line sample preparation.