Yes / Background: This study aims at characterizing the in vitro metabolism of cryptolepine using human and rat hepatocytes, identifying metabolites in rat plasma and urine after a single cryptolepine dose, and evaluating the single-dose oral and intravenous pharmacokinetics of cryptolepine in male Sprague Dawley (SD) rats. Methods: The in vitro metabolic profiles of cryptolepine were determined by LC-MS/MS following incubation with rat and human hepatocytes. The in vivo metabolic profile of cryptolepine was determined in plasma and urine samples from Sprague Dawley rats following single-dose oral administration of cryptolepine. Pharmacokinetic parameters of cryptolepine were determined in plasma and urine from Sprague Dawley rats after single-dose intravenous and oral administration. Results: Nine metabolites were identified in human and rat hepatocytes, resulting from metabolic pathways involving oxidation (M2-M9) and glucuronidation (M1, M2, M4, M8, M9). All human metabolites were found in rat hepatocyte incubations except glucuronide M1. Several metabolites (M2, M6, M9) were also identified in the urine and plasma of rats following oral administration of cryptolepine. Unchanged cryptolepine detected in urine was negligible. The Pharmacokinetic profile of cryptolepine showed a very high plasma clearance and volume of distribution (Vss) resulting in a moderate average plasma half-life of 4.5 h. Oral absorption was fast and plasma exposure and oral bioavailability were low. Conclusions: Cryptolepine metabolism is similar in rat and human in vitro with the exception of direct glucuronidation in human. Clearance in rat and human is likely to include a significant metabolic contribution, with proposed primary human metabolism pathways hydroxylation, dihydrodiol formation and glucuronidation. Cryptolepine showed extensive distribution with a moderate half-life. / Funded by Novartis Pharma under the Next Generation Scientist Program.

京都大学 / 0048 / 新制・課程博士 / 博士(薬科学) / 甲第22754号 / 薬科博第128号 / 新制||薬科||14(附属図書館) / 京都大学大学院薬学研究科医薬創成情報科学専攻 / (主査)教授 馬見塚 拓, 教授 緒方 博之, 教授 石濱 泰 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM

Gastroparesis is a disorder characterized by delayed gastric emptying due to chronic abnormal gastric motility. Prokinetic agents such as domperidone and metoclopramide are the cornerstone in treatment of gastroparesis. Although these medications have been used for decades, essential information about their metabolism is not available. Lack of knowledge about the metabolites formed in the body upon administration of the aforementioned medications as well as the enzymes involved in their metabolism limits key information needed to make sound medical decisions. Accurate and comprehensive identification of the metabolites along with reaction phenotyping of prokinetic agents will ensure safe and effective use of these drugs and hence enhance the clinical outcome. The thesis starts with an introductory chapter which comprises a comprehensive literature review on gastroparesis and the available pharmacological treatment options. The chapter also emphasizes the importance of metabolic profiling of prokinetic agents (domperidone and metoclopramide) and its impact on enhancing the safety and efficacy of these medications. Chapter 2 of this project was aimed to determine phase oxidative and conjugative metabolites of domperidone in the plasma and urine of gastroparesis patients using tandem mass spectrometry. First, the metabolites were identified in in-vitro human subcellular fractions. The knowledge gained in this experiment helped identifying the metabolites in the biological fluids of patients. In total, 12 metabolites including 7 new metabolites were identified, 5 of which were not reported previously. Chapter 3 aimed to identify the cytochrome P450 (CYP) enzymes responsible for the metabolism of metoclopramide. The parent depletion approach was used and a novel LC-MS/MS method was developed and validated to enable metoclopramide quantification. CYP2D6 was showed to the predominant isoform in metoclopramide metabolism; other isoforms also contribute to a minor extent. Chapter 4 discusses the possibility of potential drug-drug interaction (DDI) in the current management practice of gastroparesis. We identified and investigated some frequently used drug combinations that are known to share common metabolic pathways. Domperidone in combination with pioglitazone and ondansetron was evaluated. Results showed that pioglitazone inhibited domperidone metabolism in-vitro. Our experiments did not predict a DDI for the domperidone - ondansetron combination. In summary, the ultimate goal of this thesis was to improve the management of gastroparesis by increasing information about the metabolic disposition of prokinetic agents and to investigate the magnitude of putative drug combinations. The knowledge provided by this work will help in making more effective and less hazardous clinical decisions which will ultimately lead to more successful gastroparesis management. / Pharmaceutical Sciences

<div>This dissertation details three studies which utilize nontraditional applications of electrospray ionization mass spectrometry. The first study explores and discusses the limitations of identifying unknown drug metabolites using ion-molecule reactions performed inside a mass spectrometer and coupled with high performance liquid chromatography. Ultimately, it was concluded that some highly-efficient, MS² ion-molecule reactions coupled with some drug metabolites would be sufficiently sensitive for <i>in vivo</i> drug metabolism studies. However, this study also concluded that the rate of false-positives and false-negatives may be higher than previous publications suggest.</div><div><br></div><div>The next study analyzed sulfur-containing compounds under atypical negative mode electrospray ionization mass spectrometry conditions. After noting that low analyte flow rates during electrospray ionization experiments on ethanethiol resulted in significant oxygen incorporation, the aim of this study was to understand the chemistry behind the oxygen incorporation and search for ways to experimentally limit the degree of oxygen inclusion. The atypical conditions were ultimately shown to induce significant ozonolysis and other oxidation reactions. Ultimately, only the use of high flow rates or switching to a different ionization technique were successful in mitigating the oxidation product formation. A new reaction mechanism for the oxidation of ethanethiol with ozone was proposed. Quantum chemical calculations were used to support the mechanism.</div><div><br></div><div>Finally, electrospray ionization mass spectrometry was used to analyze mixtures of selenium and/or tellurium in amine-thiol solvent systems. Selenium and tellurium are essential components in many thin film solar cells and other photovoltaics and amine-thiol solvent systems have been identified as a key solution processing strategy for synthesizing selenium and tellurium thin films. However, the reaction between selenium/tellurium and the amine-thiol solvent system is poorly understood and requires detailed study before large-scale industrial synthesis can be achieved. In this study, the dissolution mechanisms for selenium and tellurium in two different amine-thiol solvent systems were explored and discussed. The role of the basicity of the amine, the relative concentrations of the thiol, and the presence of co-dissolved chalcogens were all studied and used to propose dissolution mechanisms. The results of the experiments were used to control the synthesis of lead-selenium-tellurium alloy nanoparticles and could inform further studies on controlling metal chalcogenide synthesis through the appropriate choice of amine-thiol solvents.<br></div>

Die Systematische Toxikologische Analyse (STA) stellt auf Grund der großen Vielfalt und der ständigen Zunahme an toxikologisch relevanten Substanzen eine der größten Herausforderungen in der chemischen Analyse dar. In der vorliegenden Arbeit wurde daher die Eignung der Flüssigchromatographie in Kombination mit der Hybrid-Quadrupol-Flugzeitmassenspektrometrie (LC-QTOF-MS) für diesen Zweck untersucht. Dazu wurden eine Datenbank mit über 7360 und eine CID-Spektrenbibliothek mit mehr als 2720 toxikologisch relevanten Substanzen erstellt und geeignete Probenvorbereitungsmethoden entwickelt. Die Erprobung der Methoden erfolgte an dotierten Blut- und Haarproben. Hierbei zeigte sich, dass die Analyse im Auto-MS/MS-Modus (Messzyklen von MS- und MS/MS-Spektren) eine Identifizierung basischer Substanzen mittels CID-Spektren zwischen 0,5 und 2 ng/ml im Blut ermöglichte. Die Nachweisgrenzen der für 24 Wirkstoffe validierten Methode in Haaren lagen bei 3 bis 15 pg/mg. Die Eignung der LC-QTOF-MS zur STA von Haarproben wurde an 30 Drogentodesfällen und 60 Todesfällen mit bekannter chronischer Medikamenteneinnahme zu Lebzeiten sowie an 77 Blutproben nachgewiesen. Für die Suche nach Metaboliten wurde ein Metaboliten-Tool entwickelt. In der praktischen Anwendung auf Datenfiles von Blut- und Haarproben erwies sich das Tool als wertvolles Hilfsmittel zur Identifizierung unbekannter Peaks und zur Bestätigung von Suchergebnissen in der Datenbank. Zur automatischen Konzentrationsabschätzung identifizierter Substanzen wurde ein Tool „Estimate Concentration“ geschaffen. Die Überprüfung des Verfahrens an realen Blut- und Haarproben durch Vergleich mit HPLC-DAD- und GC-MS-Ergebnissen wies eine gute Übereinstimmung der Konzentrationen auf. Insgesamt zeigten die Untersuchungen, dass die LC-QTOF-MS zurzeit die am besten geeignete Methode für die STA darstellt. Auch bei einem erst später aufkommenden Verdacht kann eine gezielte Suche in dem bereits gemessenen Datenfile durchgeführt werden. / Due to the large variety and the steady increase of toxicologically relevant substances, systematic toxicological analysis (STA) is one of the most difficult tasks in analytical chemistry and, therefore, a steady topic of research and methodical improvement. For this reason, the suitability of liquid chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) for STA was investigated. For this purpose, a database of more than 7360 and a CID spectra library of more than 2720 toxicologically relevant substances and suitable methods for sample preparation were developed. The application was evaluated at spiked blood and hair samples. It was found that the analysis in Auto-MS/MS mode (alternating measurement cycles of MS and MS/MS spectra) allowed substance identification in blood using CID spectra between 0.5 and 2 ng/ml for basic substances. The detection limits of the validated method in hair ranged from 3 to 15 pg/mg for 24 drugs. The suitability of LC-QTOF-MS for STA was tested for hair samples from 30 drug-related death cases and from 60 death cases with known chronic medication as well as for 77 blood samples. For the search of metabolites, a metabolite tool was developed. In the practical application to data files from blood and hair samples, the tool proved to be very helpful for identification of unknown peaks and for confirmation of results obtained only from the database without CID spectra. A tool "Estimate Concentration" was created for automatic estimation of concentrations of identified substances. The application to real blood and hair samples and the comparison of the concentrations with results from HPLC-DAD and GC-MS showed good agreement. Overall, these investigations showed that LC-QTOF-MS is currently the most favorable method for STA. Because of the comprehensive registration of all substances in a sample, the data files can be checked for the presence of certain poisons even later without new measurements.