Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Drug Metab Dispos. 2013 Sep;41(9):1651-61. doi: 10.1124/dmd.113.051094. Epub 2013 Jun 18.
Vinorelbine is a semisynthetic vinca alkaloid used in the treatment of advanced breast and non-small cell lung cancers. Vincristine, a related vinca alkaloid, is 9-fold more efficiently metabolized by CYP3A5 than by CYP3A4 in vitro. This study quantified the relative contribution of CYP3A4 and CYP3A5 to the metabolism of vinorelbine in vitro using cDNA-expressed human cytochrome P450s (P450s) and human liver microsomes (HLMs). CYP3A4 and CYP3A5 were identified as the P450s capable of oxidizing vinorelbine using a panel of human enzymes and selective P450 inhibitors in HLMs. For CYP3A4 coexpressed with cytochrome b5 (CYP3A4+b5) and CYP3A5+b5, the Michaelis-Menten constants for vinorelbine were 2.6 and 3.6 μM, respectively, but the Vmax of 1.4 pmol/min/pmol was common to both enzymes. In HLMs, the intrinsic clearance of vinorelbine metabolism was highly correlated with CYP3A4 activity, and there was no significant difference in intrinsic clearance between CYP3A5 high and low expressers. When radiolabeled vinorelbine substrate was used, there were clear qualitative differences in metabolite formation fingerprints between CYP3A4+b5 and CYP3A5+b5 as determined by NMR and mass spectrometry analysis. One major metabolite (M2), a didehydro-vinorelbine, was present in both recombinant and microsomal systems but was more abundant in CYP3A4+b5 incubations. We conclude that despite the equivalent efficiency of recombinant CYP3A4 and CYP3A5 in vinorelbine metabolism the polymorphic expression of CYP3A5, as shown by the kinetics with HLMs, may have a minimal effect on systemic clearance of vinorelbine.
长春瑞滨是一种半合成长春碱类药物，用于治疗晚期乳腺癌和非小细胞肺癌。长春新碱是一种相关的长春碱类药物，在体外比 CYP3A4 更有效地被 CYP3A5 代谢 9 倍。本研究使用 cDNA 表达的人细胞色素 P450（P450）和人肝微粒体（HLM），定量研究了 CYP3A4 和 CYP3A5 对长春瑞滨体外代谢的相对贡献。使用 HLMs 中的人酶和选择性 P450 抑制剂鉴定 CYP3A4 和 CYP3A5 为能够氧化长春瑞滨的 P450。对于与细胞色素 b5（CYP3A4+b5）共表达的 CYP3A4 和 CYP3A5+b5，长春瑞滨的米氏常数分别为 2.6 和 3.6 μM，但两种酶的 Vmax 均为 1.4 pmol/min/pmol。在 HLMs 中，长春瑞滨代谢的内在清除率与 CYP3A4 活性高度相关，CYP3A5 高表达者和低表达者之间的内在清除率没有显著差异。当使用放射性标记的长春瑞滨底物时，通过 NMR 和质谱分析，在 CYP3A4+b5 和 CYP3A5+b5 之间清楚地观察到代谢产物形成指纹的定性差异。一种主要代谢产物（M2），一种脱氢长春瑞滨，在重组和微粒体系统中均存在，但在 CYP3A4+b5 孵育中更为丰富。我们得出结论，尽管重组 CYP3A4 和 CYP3A5 在长春瑞滨代谢中的效率相当，但 CYP3A5 的多态性表达，如与 HLMs 的动力学所示，可能对长春瑞滨的全身清除率影响最小。
