Future technology insight: mass spectrometry imaging as a tool in drug research and development (original) (raw)
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Scientific Reports, 2016
Liquid extraction surface analysis mass spectrometry imaging (LESA-MSI) has been shown to be an effective tissue profiling and imaging technique, producing robust and reliable qualitative distribution images of an analyte or analytes in tissue sections. Here, we expand the use of LESA-MSI beyond qualitative analysis to a quantitative analytical technique by employing a mimetic tissue model previously shown to be applicable for MALDI-MSI quantitation. Liver homogenate was used to generate a viable and molecularly relevant control matrix for spiked drug standards which can be frozen, sectioned and subsequently analyzed for the generation of calibration curves to quantify unknown tissue section samples. The effects of extraction solvent composition, tissue thickness and solvent/ tissue contact time were explored prior to any quantitative studies in order to optimize the LESA-MSI method across several different chemical entities. The use of a internal standard to normalize regional differences in ionization response across tissue sections was also investigated. Data are presented comparing quantitative results generated by LESA-MSI to LC-MS/MS. Subsequent analysis of adjacent tissue sections using DESI-MSI is also reported. A drugs distribution and the relationship with efficacy and safety are important considerations during drug development. It is crucial that a compound is present in sufficient quantity at the site of action to deliver efficacy. Equally, excessive abundance of the drug in tissues may lead to unwanted toxicological findings rendering the drug unsafe. Drug distribution has historically been assessed in various ways. Tissue homogenization techniques, coupled to liquid chromatography and mass spectrometry have been the mainstay to quantify drugs in tissues 1. However, this approach results in the loss of all spatial information from the sample and merely provides an average concentration within the tissue. There is also a risk of variation caused by residual blood contamination. Mapping and quantifying the distribution of compounds in vivo was historically performed using radiolabeled compounds in techniques such as quantitative whole body autoradiography (QWBA) 2,3. The technique is reliable, sensitive, quantitative and retains meaningful spatial information. However, the necessity for a radiolabeled compound is a major drawback that can lead to significant 'synthesis' delays. Furthermore, quantitation of the parent drug can be misrepresented due to drug metabolites that still include the radiolabel. Mass spectrometry imaging (MSI) is a complementary, viable, multiplex and label free way of elucidating the distribution of drugs and endogenous metabolites directly from the surface of tissue sections 4. MSI is a term used to describe a group of complementary surface sampling technologies based on different mass spectrometry ionization methods. The most commonly used are matrix assisted laser desorption ionization (MALDI-MSI) 5-7 , secondary ion mass spectrometry (SIMS-MSI) 8 , desorption electrospray ionization (DESI-MSI) 9,10 and nanoelectrospray ionization based liquid microjunction techniques such as liquid extraction surface analysis (LESA-MSI) 11,12. Each technique has innate advantages and disadvantages in sensitivity, speed and spatial resolution.
Experimental Models to Study Drug Distributions in Tissue Using MALDI Mass Spectrometry Imaging
Journal of Proteome Research, 2013
Requirements for patient safety and improved efficacy are steadily increasing in modern healthcare and are key drivers in modern drug development. New drug characterization assays are central in providing evidence of the specificity and selectivity of drugs. Meeting this need, matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) is used to study drug localization within microenvironmental tissue compartments. Thin sections of human lung tumor and rat xenograft tissues were exposed to pharmaceutical drugs by either spotting or submerging. These drugs, the epidermal growth factor receptor antagonists, erlotinib (Tarceva) and gefitinib (Iressa), and the acetylcholine receptor antagonist, tiotropium, were characterized by microenvironment localization. Intact tissue blocks were also immersed in drug solution, followed by sectioning. MALDI-MSI was then performed using a Thermo MALDI LTQ Orbitrap XL instrument to localize drug-distribution patterns. We propose three MALDI-MSI models measuring drug disposition that have been used to map the selected compounds within tissue compartments of tumors isolated from lung cancer patients.
PLoS ONE, 2010
Readouts that define the physiological distributions of drugs in tissues are an unmet challenge and at best imprecise, but are needed in order to understand both the pharmacokinetic and pharmacodynamic properties associated with efficacy. Here we demonstrate that it is feasible to follow the in vivo transport of unlabeled drugs within specific organ and tissue compartments on a platform that applies MALDI imaging mass spectrometry to tissue sections characterized with high definition histology. We have tracked and quantified the distribution of an inhaled reference compound, tiotropium, within the lungs of dosed rats, using systematic point by point MS and MS/MS sampling at 200 mm intervals. By comparing drug ion distribution patterns in adjacent tissue sections, we observed that within 15 min following exposure, tiotropium parent MS ions (mass-to-charge; m/z 392.1) and fragmented daughter MS/MS ions (m/z 170.1 and 152.1) were dispersed in a concentration gradient (80 fmol-5 pmol) away from the central airways into the lung parenchyma and pleura. These drug levels agreed well with amounts detected in lung compartments by chemical extraction. Moreover, the simultaneous global definition of molecular ion signatures localized within 2-D tissue space provides accurate assignment of ion identities within histological landmarks, providing context to dynamic biological processes occurring at sites of drug presence. Our results highlight an important emerging technology allowing specific high resolution identification of unlabeled drugs at sites of in vivo uptake and retention.
DESI-Mass Spectrometry Imaging Investigation of Discrete and Cassette Drug Dosed Tissues
2017
This technique requires the introduction of a radiolabel to the synthesis of the drug, and then allows the visualization of the radiolabel in a quantitative, sensitive manner. However, as it relies on the detection of the radiolabel, WBA is unable to distinguish between the parent compound and any potential metabolites that could also contain the radiolabel. Furthermore, to synthesize the Mass spectrometry imaging for the distribution of drugs and their associated metabolites, a DMPK solution.
Quantitative mass spectrometry imaging of drugs and metabolites: a multiplatform comparison
Analytical and Bioanalytical Chemistry
Mass spectrometry imaging (MSI) provides insight into the molecular distribution of a broad range of compounds and, therefore, is frequently applied in the pharmaceutical industry. Pharmacokinetic and toxicological studies deploy MSI to localize potential drugs and their metabolites in biological tissues but currently require other analytical tools to quantify these pharmaceutical compounds in the same tissues. Quantitative mass spectrometry imaging (Q-MSI) is a field with challenges due to the high biological variability in samples combined with the limited sample cleanup and separation strategies available prior to MSI. In consequence, more selectivity in MSI instruments is required. This can be provided by multiple reaction monitoring (MRM) which uses specific precursor ion-product ion transitions. This targeted approach is in particular suitable for pharmaceutical compounds because their molecular identity is known prior to analysis. In this work, we compared different analytica...
Analytical Chemistry, 2014
Drug efficacy strongly depends on the presence of the drug substance at the target site. As vascularization is an important factor for the distribution of drugs in tissues, we analyzed drug distribution as a function of blood vessel localization in tumor tissue. To explore distribution of the anticancer drugs afatinib, erlotinib, and sorafenib, a combined approach of matrix-assisted laser desorption/ionization (MALDI) drug imaging and immunohistochemical vessel staining was applied and examined by digital image analysis. The following two xenograft models were investigated: (1) mice carrying squamous cell carcinoma (FaDu) xenografts (n tumor = 13) were treated with afatinib or erlotinib, and (2) sarcoma (A673) xenograft bearing mice (n tumor = 8) received sorafenib treatment. MALDI drug imaging revealed a heterogeneous distribution of all anticancer drugs. The tumor regions containing high drug levels were associated with a higher degree of vascularization than the regions without drug signals (p < 0.05). When correlating the impact of blood vessel size to drug abundance in the sarcoma model, a higher amount of small vessels was detected in the tumor regions with high drug levels compared to the tumor regions with low drug levels (p < 0.05). With the analysis of coregistered MALDI imaging and CD31 immunohistochemical data by digital image analysis, we demonstrate for the first time the potential of correlating MALDI drug imaging and immunohistochemistry. Here we describe a specific and precise approach for correlating histological features and pharmacokinetic properties of drugs at microscopic level, which will provide information for the improvement of drug design, administration formula or treatment schemes.
Bioanalysis of drug in tissue: current status and challenges
Bioanalysis, 2012
Distribution of drugs into tissues is an important determinant of the overall PK and PD profile. Thus, bioanalysis of drugs and their metabolites in tissues can play an important role in understanding the pharmacological and toxicological properties of new drug candidates. Unlike liquid matrices, bioanalysis in tissues offers unique challenges such as proper tissue sampling, appropriate tissue sample preparation, efficient extraction of the analytes from the tissue homogenates, and demonstration of stability and recovery of analytes in intact tissues. This article provides a systematic review of tissue sample analysis for small molecules using LC–MS/MS. The authors provide rationale for tissue sample analysis, and discuss strategies for method development, method qualification or validation, and sample analysis. Unique aspects of method development and qualification/validation are highlighted based on authors’ direct experiences and literature summary. Analysis using intact tissue s...
Analytical chemistry, 2015
Liquid extraction surface analysis mass spectrometry (LESA-MS) is a surface sampling technique that incorporates liquid extraction from the surface of tissue sections with nanoelectrospray mass spectrometry. Traditional tissue analysis techniques usually require homogenization of the sample prior to analysis via high-performance liquid chromatography mass spectrometry (HPLC-MS), but an intrinsic weakness of this is a loss of all spatial information and the inability of the technique to distinguish between actual tissue penetration and response caused by residual blood contamination. LESA-MS, in contrast, has the ability to spatially resolve drug distributions and has historically been used to profile discrete spots on the surface of tissue sections. Here, we use the technique as a mass spectrometry imaging (MSI) tool, extracting points at 1 mm spatial resolution across tissue sections to build an image of xenobiotic and endogenous compound distribution to assess drug blood-brain bar...
Analytical Chemistry, 2011
Quantitative determination of drug concentrations in tissue homogenates via liquid chromatographyÀtandem mass spectrometry (LC-MS/MS) is commonly conducted using the standards and analytical quality controls (QCs) prepared in the same matrix (tissue homogenates), to keep the matrix and its effects consistent on the analytes during sample extraction and analysis. In this manuscript, we proposed to analyze tissue homogenate samples using an LC-MS/ MS assay with the standards and analytical QCs prepared in plasma after tissue homogenate samples were appropriately diluted with plasma. BMS-650032 was used as a model compound, and its validated dog plasma assay was used for dog liver sample analyses. The tissue matrix effect was evaluated by diluting liver homogenate QCs with drug-free plasma at different dilution factors to determine the minimum required dilution factor (MRDF) at which tissue matrix has insignificant impact to the plasma assay. The percentage deviation of the measured concentration from the nominal concentration was used as an indicator of the tissue matrix effect. The results suggested that the tissue matrix effect was decreased as the plasma dilution factor increased. Based on the results of the tissue matrix effect evaluation, liver homogenate samples were analyzed after appropriate dilutions with plasma at the MRDF or greater dilution factors. The results confirmed that this approach generates accurate data, and the process is very convenient and economic. This approach has been used on the analyses of different tissues (liver and brain) and biofluid (bile) to support several drug development programs.
Imaging mass spectrometry: challenges in visualization of drug distribution in solid tumors
Current Opinion in Pharmacology, 2013
Mass spectrometry imaging (MSI) is an emerging technique that allows molecular visualization of the distribution of drugs and metabolites in a two-dimensional space directly in biological tissues. Imaging drug distribution inside a tumor is an important tool to support strategies to improve penetration of anticancer drugs and consequently the outcome of chemotherapy. MSI has some advantages in comparison to other imaging techniques, that is, whole body autoradiography, positron emission tomography or microscopy imaging. It is a label-free technique with better specificity and provides the possibility to combine histological data with MS ones and to visualize simultaneously the distribution of biomarkers in relation to tumor heterogeneity. We overview here publications on MSI applied to studies of the distribution of anticancer agents in tumor tissue. In addition, we focused our attention on technical limitations and future perspectives pertaining to this technique.