Department of Pharmaceutical Sciences, Lipscomb University College of Pharmacy and Health Sciences, Nashville, Tennessee (J.E.B., V.T., A.A.A., K.J.W., R.D.C., K.D.J.); Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee (R.D.C., K.D.J.); and Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (K.D.J.).
Department of Pharmaceutical Sciences, Lipscomb University College of Pharmacy and Health Sciences, Nashville, Tennessee (J.E.B., V.T., A.A.A., K.J.W., R.D.C., K.D.J.); Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee (R.D.C., K.D.J.); and Division of Pharmacotherapy and Experimental Therapeutics, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina (K.D.J.)
Drug Metab Dispos. 2019 Nov;47(11):1257-1269. doi: 10.1124/dmd.119.088823. Epub 2019 Sep 6.
Lapatinib is a dual tyrosine kinase inhibitor associated with rare but potentially severe idiosyncratic hepatotoxicity. We have previously shown that cytochromes P450 CYP3A4 and CYP3A5 quantitatively contribute to lapatinib bioactivation, leading to formation of a reactive, potentially toxic quinone imine. CYP3A5 is highly polymorphic; however, the impact of CYP3A5 polymorphism on lapatinib metabolism has not been fully established. The goal of this study was to determine the effect of genotype and individual variation in CYP3A activity on the metabolic activation of lapatinib using human-relevant in vitro systems. Lapatinib metabolism was examined using -genotyped human liver microsomes and cryopreserved human hepatocytes. CYP3A and CYP3A5-selective activities were measured in liver tissues using probe substrates midazolam and T-5 (T-1032), respectively, to evaluate the correlation between enzymatic activity and lapatinib metabolite formation. Drug metabolites were measured by high-performance liquid chromatography-tandem mass spectrometry. Further, the relative contributions of CYP3A4 and CYP3A5 to lapatinib -debenzylation were estimated using selective chemical inhibitors of CYP3A. The results from this study demonstrated that lapatinib -debenzylation and quinone imine-GSH conjugate formation were highly correlated with hepatic CYP3A activity, as measured by midazolam 1'-hydroxylation. CYP3A4 played a dominant role in lapatinib bioactivation in all liver tissues evaluated. The CYP3A5 contribution to lapatinib bioactivation varied by individual donor and was dependent on CYP3A5 genotype and activity. CYP3A5 contributed approximately 20%-42% to lapatinib -debenzylation in livers from CYP3A5 expressers. These findings indicate that individual CYP3A activity, not genotype alone, is a key determinant of lapatinib bioactivation and likely influences exposure to reactive metabolites. SIGNIFICANCE STATEMENT: This study is the first to examine the effect of genotype, total CYP3A activity, and CYP3A5-selective activity on lapatinib bioactivation in individual human liver tissues. The results of this investigation indicate that lapatinib bioactivation via oxidative -debenzylation is highly correlated with total hepatic CYP3A activity, and not genotype alone. These findings provide insight into the individual factors, namely, CYP3A activity, that may affect individual exposure to reactive, potentially toxic metabolites of lapatinib.
拉帕替尼是一种双重酪氨酸激酶抑制剂，与罕见但潜在严重的个体过敏反应性肝毒性有关。我们之前已经表明，细胞色素 P450 CYP3A4 和 CYP3A5 定量参与拉帕替尼的生物激活，导致形成反应性、潜在毒性的醌亚胺。CYP3A5 高度多态性；然而，CYP3A5 多态性对拉帕替尼代谢的影响尚未完全确定。本研究的目的是使用与人类相关的体外系统确定基因型和 CYP3A 活性个体变异对拉帕替尼代谢激活的影响。使用 -基因分型的人肝微粒体和冷冻保存的人肝细胞研究拉帕替尼的代谢。使用探针底物咪达唑仑和 T-5（T-1032）分别测量肝组织中的 CYP3A 和 CYP3A5 选择性活性，以评估酶活性与拉帕替尼代谢物形成之间的相关性。使用高效液相色谱-串联质谱法测量药物代谢物。此外，使用 CYP3A 的选择性化学抑制剂估计 CYP3A4 和 CYP3A5 对拉帕替尼 -去苯甲酰化的相对贡献。这项研究的结果表明，拉帕替尼 -去苯甲酰化和醌亚胺 -谷胱甘肽缀合物的形成与肝 CYP3A 活性高度相关，这通过咪达唑仑 1'-羟化来测量。在所有评估的肝组织中，CYP3A4 在拉帕替尼的生物激活中起主导作用。CYP3A5 对拉帕替尼生物激活的贡献因个体供体而异，并且依赖于 CYP3A5 基因型和活性。CYP3A5 在 CYP3A5 表达者的肝脏中对拉帕替尼 -去苯甲酰化的贡献约为 20%-42%。这些发现表明，个体 CYP3A 活性而不是 基因型单独是拉帕替尼生物激活的关键决定因素，并且可能影响对反应性代谢物的暴露。意义声明：本研究首次研究了 基因型、总 CYP3A 活性和 CYP3A5 选择性活性对个体人肝组织中拉帕替尼生物激活的影响。该研究的结果表明，通过氧化 -去苯甲酰化的拉帕替尼生物激活与总肝 CYP3A 活性高度相关，而不仅仅是 基因型。这些发现提供了对个体因素的深入了解，即 CYP3A 活性，这些因素可能会影响个体对拉帕替尼的反应性、潜在毒性代谢物的暴露。
