In vitro glucuronidation of the primary metabolite of 10-chloromethyl-11-demethyl-12-oxo-calanolide A by human liver microsomes and its interactions with UDP-glucuronosyltransferase substrates

The Ontogeny of UDP-glucuronosyltransferase Enzymes, Recommendations for Future Profiling Studies and Application Through Physiologically Based Pharmacokinetic Modelling

Limited understanding of drug pharmacokinetics in children is one of the major challenges in paediatric drug development. This is most critical in neonates and infants owing to rapid changes in physiological functions, especially in the activity of drug-metabolising enzymes. Paediatric physiologically based pharmacokinetic models that integrate ontogeny functions for cytochrome P450 enzymes have aided our understanding of drug exposure in children, including those under the age of 2 years. Paediatric physiologically based pharmacokinetic models have consequently been recognised by the European Medicines Agency and the US Food and Drug Administration as innovative tools in paediatric drug development and regulatory decision making. However, little is currently known about age-related changes in UDP-glucuronosyltransferase-mediated metabolism, which represents the most important conjugation reaction for xenobiotics. Therefore, the objective of the review was to conduct a thorough literature survey to summarise our current understanding of age-related changes in UDP-glucuronosyltransferases as well as associated clinical and experimental sources of variance. Our findings indicate that there are distinct differences in UDP-glucuronosyltransferase expression and activity between isoforms for different age groups. In addition, there is substantial variability between individuals and laboratories reported for human liver microsomes, which results in part from a lack of standardised experimental conditions. Therefore, we provide a number of best practice recommendations for experimental conditions, which ultimately may help improve the quality of data used for quantitative clinical pharmacology approaches, and thus for safe and effective pharmacotherapy in children.

Synthesis and Characterization of a Novel Mycophenolic Acid-Quinic Acid Conjugate Serving as Immunosuppressant with Decreased Toxicity

Mycophenolic acid (MPA) is one of the most commonly used immunosuppressive drugs for improving the outcome of cell and organ transplantations. However, an undesired adverse effect of MPA impedes its application in the clinics for post-transplant patients. By conjugating MPA to quinic acid (QA) via amide bonds, we synthesized a novel immunosuppressant, N-[2-[[(4E)-6-(1,3-dihydro-4-hydroxy-6-methoxy-7-methyl-3-oxo-5-isobenzofuranyl)-4-methyl-1-oxo-4-hexen-1-yl]amino]ethyl]-(1α,3R,4α,5R)-1,3,4,5-tetrakis(acetyloxy)cyclohexanecarboxamide (abbreviated as MQ4), which exhibits improved stability demonstrated by its incubation in vitro with human plasma, suggesting its better resistance to hydrolytic degradation induced by plasma enzyme. While the immunosuppressive effect of MQ4 on human lymphocyte proliferation was partially compromised as shown by flow cytometry, significant decrease in cytotoxicity of MQ4 to insulin producing β cells could compensate this drawback to some degree. There was a decreased level of apoptotic mediator caspase-3, which may contribute to the decreased toxicity of MQ4 to INS-1E cells. MQ4 could further improve insulin stimulation index and downregulate NFκB expression compared to physical mixing of QA to MPA. Taken together, MQ4 is a promising immunosuppressive agent for preventing and minimizing post-transplanted immune rejection.