Investigation of Figopitant and Its Metabolites in Rat Tissue by Combining Whole-Body Autoradiography with Liquid Extraction Surface Analysis Mass Spectrometry

Abstract

ABSTRACT:This article describes the combination of whole-body autoradiography with liquid extraction surface analysis (LESA) and mass spectrometry (MS) to study the distribution of the tachykinin neurokinin-1 antagonist figopitant and its metabolites in tissue sections of rats after intravenous administration of 5.0 mg/kg figopitant. An overview of autoradiography results is presented together with mass spectrometry identification and semiquantification of parent drug and its metabolites based on LESA-MS. The quality and accuracy of data generated by LESA-MS were assessed in comparison with classic tissue extraction, sample cleanup, and high-performance liquid chromatography analysis. The parent drug and the N-dealkylated metabolite M474(1) (BIIF 1148) in varying ratios were the predominant compounds in all tissues investigated. In addition, several metabolites formed by oxygenation, dealkylation, and a combination of oxygenation and dealkylation were identified. In summary, the LESA-MS technique was shown to be a powerful tool for identification and semiquantification of figopitant and its metabolites in different tissues and was complementary to quantitative whole-body autoradiography for studying the distribution. IntroductionQuantitative whole-body autoradiography (QWBA) is the imaging method of choice to investigate the distribution of drug-related radioactivity in all organs and tissues of an intact organism, such as an animal carcass. With this technique, information on the concentration of the entire drug-related radioactivity is gained. However, the actual molecular entity-parent compound or metabolites-and their respective proportions of the radioactivity remains unknown. The conventional approach to identify and quantify parent drug and metabolites in tissues is the preparation of organ homogenates and sample analysis by liquid chromatography combined with radiodetection and tandem mass spectrometry (MS/MS). However, this approach is labor-intensive, and some tissues (e.g., salivary glands) and tissue substructures (e.g., renal inner and outer medulla) can be difficult or even impossible to sample and extract. Surface sampling methods such as desorption electrospray ionization, laser desorption ionization, direct analyses in real time, or matrix-assisted laser desorption ionization can speed up analysis time and cut overall costs compared with classic tissue extraction and enable spatial resolution of different anatomical substructures within a given organ (Reyzer et al., 2003).Recently, a fully automated liquid extraction-based surface sampling method for mass spectrometry (MS) analyses of drugs and metabolites in thin tissue sections has been described (Van Berkel and Kertesz, 2009;Kertesz and Van Berkel, 2010). This liquid extraction surface analysis (LESA) method uses a liquid microjunction probe to extract the analytes directly from the surface followed by automated nano-electrospray analysis. Direct surface sampling methods deal with high sample complexity, because no chromatographic separation ...

Mass spectrometry imaging for drug distribution studies

“…Additional studies have shown LESA to provide semi-quantitative distribution data for drugs and their metabolites, which was in agreement with quantitative WBA [107,108].…”

Ambient Mass Spectrometry Imaging Using Direct Liquid Extraction Techniques

“…84 Such “contact” model LESA may be advantageous for the analysis of samples containing a protective layer on the surface. When installed on a fully automated robotic system, it enables high-throughput, spatially resolved analysis of metabolites, 85,86 lipids, 87–90 and proteins 91,92 in complex samples, including dried blood spots, 84,88 contact lenses, 89 tissues, 55,83,86,91 and microbial colonies. 84,93 LESA also has been used for analyzing molecules separated using TLC 83 and capillary electrophoresis.…”

“…86 While autoradiography enabled quantitative high-resolution imaging of the labeled figopitant, it could not distinguish between the drug and drug metabolites as both contained the isotopic label. LESA MS proved to be superior for the identification of drug and drug metabolites.…”

“…LESA MS proved to be superior for the identification of drug and drug metabolites. 86 In another study, Prideaux et al performed imaging of levofloxacin in rat lung tissue infected with tuberculosis using Flowprobe MSI. 155 The tissue was imaged by extracting material from positions separated by 630 µm over the entire tissue section.…”

Liquid Microjunction Surface Sampling of Acetaminophen, Terfenadine and Their Metabolites in Thin Tissue Sections

“…This challenge is perfectly suited for liquid extraction-based surface sampling probes [8] that have been successfully used with MS for detecting drugs [9] and Phase I [10][11][12], and II metabolites [13][14][15][16][17][18] from animal thin tissue sections. More importantly, integration with HPLC-MS/MS systems was accomplished for both the sealing surface-sampling probe [19,20] and various liquid microjunction surface-sampling probe configurations [16][17][18] to increase sensitivity of the analyses.…”