Department of Pharmaceutical Sciences, Washington State University, Spokane, Washington (M.M.P., A.B., B.P.); Departments of Chemistry, Biochemistry, and Microbiology, and the Integrated Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (P.B.J., M.R.R.); SOLVO Biotechnology, Budapest, Hungary (Z.G., E.K.); and BioIVT Inc., Baltimore, Maryland (S.H.).
Department of Pharmaceutical Sciences, Washington State University, Spokane, Washington (M.M.P., A.B., B.P.); Departments of Chemistry, Biochemistry, and Microbiology, and the Integrated Program for Biological and Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (P.B.J., M.R.R.); SOLVO Biotechnology, Budapest, Hungary (Z.G., E.K.); and BioIVT Inc., Baltimore, Maryland (S.H.)
Drug Metab Dispos. 2021 Aug;49(8):683-693. doi: 10.1124/dmd.121.000476. Epub 2021 Jun 1.
The anticancer drug irinotecan shows serious dose-limiting gastrointestinal toxicity regardless of intravenous dosing. Although enzymes and transporters involved in irinotecan disposition are known, quantitative contributions of these mechanisms in complex in vivo disposition of irinotecan are poorly understood. We explained intestinal disposition and toxicity of irinotecan by integrating 1) in vitro metabolism and transport data of irinotecan and its metabolites, 2) ex vivo gut microbial activation of the toxic metabolite SN-38, and 3) the tissue protein abundance data of enzymes and transporters relevant to irinotecan and its metabolites. Integration of in vitro kinetics data with the tissue enzyme and transporter abundance predicted that carboxylesterase (CES)-mediated hydrolysis of irinotecan is the rate-limiting process in the liver, where the toxic metabolite formed is rapidly deactivated by glucuronidation. In contrast, the poor SN-38 glucuronidation rate as compared with its efficient formation by CES2 in the enterocytes is the key mechanism of the intestinal accumulation of the toxic metabolite. The biliary efflux and organic anion transporting polypeptide-2B1-mediated enterocyte uptake can also synergize buildup of SN-38 in the enterocytes, whereas intestinal P-glycoprotein likely facilitates SN-38 detoxification in the enterocytes. The higher SN-38 concentration in the intestine can be further nourished by β-d-glucuronidases. Understanding the quantitative significance of the key metabolism and transport processes of irinotecan and its metabolites can be leveraged to alleviate its intestinal side effects. Further, the proteomics-informed quantitative approach to determine intracellular disposition can be extended to determine susceptibility of cancer cells over normal cells for precision irinotecan therapy. SIGNIFICANCE STATEMENT: This work provides a deeper insight into the quantitative relevance of irinotecan hydrolysis (activation), conjugation (deactivation), and deconjugation (reactivation) by human or gut microbial enzymes or transporters. The results of this study explain the characteristic intestinal exposure and toxicity of irinotecan. The quantitative tissue-specific in vitro to in vivo extrapolation approach presented in this study can be extended to cancer cells.
伊立替康是一种抗癌药物，无论静脉给药剂量如何，都会产生严重的剂量限制胃肠道毒性。尽管已知参与伊立替康处置的酶和转运体，但在伊立替康复杂的体内处置中，这些机制的定量贡献仍知之甚少。我们通过整合 1）伊立替康及其代谢物的体外代谢和转运数据，2）有毒代谢物 SN-38 的肠道微生物体外激活，以及 3）与伊立替康及其代谢物相关的酶和转运体的组织蛋白丰度数据，解释了伊立替康的肠道处置和毒性。将体外动力学数据与组织酶和转运体丰度相结合，预测了羧酸酯酶（CES）介导的伊立替康水解是肝脏中限速的过程，在肝脏中形成的有毒代谢物很快被葡萄糖醛酸化失活。相比之下，SN-38 葡萄糖醛酸化率低，而 CES2 在肠细胞中高效形成 SN-38，是有毒代谢物在肠细胞中积累的关键机制。胆汁外排和有机阴离子转运多肽 2B1 介导的肠细胞摄取也可以协同促进 SN-38 在肠细胞中的积累，而肠 P-糖蛋白可能有助于肠细胞中 SN-38 的解毒。较高的 SN-38 浓度在肠道中可以通过β-d-葡萄糖醛酸酶进一步得到滋养。了解伊立替康及其代谢物的关键代谢和转运过程的定量意义，可以减轻其肠道副作用。此外，基于蛋白质组学的定量方法来确定细胞内处置也可以扩展到确定癌细胞对正常细胞的易感性，以实现精准伊立替康治疗。意义陈述：本工作更深入地了解了人类或肠道微生物酶或转运体对伊立替康水解（激活）、结合（失活）和去结合（再激活）的定量相关性。本研究的结果解释了伊立替康的特征性肠道暴露和毒性。本研究中提出的定量组织特异性体外到体内外推方法可以扩展到癌细胞。
