Characterization of a Novel Selective Cytochrome P450 3A5 Substrate

新型选择性细胞色素 P450 3A5 底物的表征

• 批准号: 8227548
• 负责人: Michael Darin Cameron
• 金额: $ 24.75万
• 依托单位: SCRIPPS FLORIDA
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-06-10 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8227548
• 关键词: African American; Alleles; Area; Biological Assay; CYP1A2 gene; CYP2D6 gene; CYP3A4 gene; CYP3A5 gene; Caucasians; Caucasoid Race; Chemicals; Clinical; Communities; Conduct Clinical Trials; Cytochrome P450; Data; Dose; Drug Interactions; Drug Kinetics; Drug Metabolism Inhibition; Drug Prescriptions; Enzymes; Exhibits; Family; Genes; Genetic; Genetic Polymorphism; Genotype; Goals; Grapefruit juice; Hepatic; Human; Hydroxylation; Immunosuppressive Agents; In Vitro; Individual; Individual Differences; Ketoconazole; Kinetics; Laboratories; Literature; Liver; Liver Microsomes; Measures; Metabolism; Microsomes; Midazolam; Omeprazole; Overdose; Pathway interactions; Patients; Pharmaceutical Preparations; Pharmacologic Substance; Predisposition; Process; Proteins; Quality Control; RNA Splicing; Recombinants; Reporting; Research; Research Personnel; Rifampin; Role; Safety; Sampling; Tacrolimus; Testosterone; Time; Toxic effect; Validation; Variant; Work; Xenobiotics; analog; analytical method; base; cytochrome P450 3A; design; drug discovery; drug metabolism; expectation; in vitro Assay; inhibitor/antagonist; milligram; morpholine; novel; racial difference; scale up; success; tandem mass spectrometry; therapeutic target; tool

DESCRIPTION (provided by applicant): It is widely accepted that patients on multiple medications are susceptible to pharmacokinetic drug-drug interactions when one of the drugs interferes with the activity of key enzymes involved in drug metabolism, chiefly enzymes in the cytochrome P450 family. In the past decade the FDA has commonly required companies to conduct clinical trials to determine the result of such drug-drug interactions. Some drugs such as ketoconazole have been shown to inhibit the activity of individual P450 enzymes; while other drugs such as rifampicin or omeprazole induce expression of higher P450 levels in the liver. These interactions can require dose adjustments to avoid having elevated drug concentrations and potentially increasing toxicities or having insufficient drug levels to be efficacious. Existing in vitro tools can reasonably predict compounds that are likely to cause most of the common metabolism-based drug-drug interactions. However, tools are not currently available to distinguish between the major CYP3A enzymes, CYP3A4 and CYP3A5. These two enzymes are implicated in the metabolism of more pharmaceuticals than any other P450s. Alteration of CYP3A4/5 activity can have serious consequences and drugs that are metabolized through this pathway often come with warnings: not to take with grapefruit juice, ketoconazole, St. Johns Wart, and numerous other CYP3A inhibitors or inducers. CYP3A5 may be the most important genetic contributor to interindividual and interracial differences in the metabolism of prescription drugs. Individuals with at least one gene for the active CYP3A5*1 allele express large amounts of functional CYP3A5, whereas CYP3A5*3*3 causes a splice variant that results in minimal CYP3A5 expression. Approximately 60% of African Americans and 30% of Caucasians have at least one *1 allele and express roughly equivalent levels of CYP3A5 and CYP3A4. CYP3A4 and CYP3A5 activity cannot be clearly differentiated in biologically relevant samples. Currently, the data for CYP3A inhibition of almost every approved compound is generated using a CYP3A assay measuring testosterone hydroxylation or midazolam hydroxylation by pooled human liver microsomes. While both of these substrates are metabolized by CYP3A4 and CYP3A5, the resulting inhibition constants primarily reflect CYP3A4 because multiple donor pools of hepatic microsomes contain approximately five to six times more CYP3A4 than CYP3A5. We have identified the first highly selective substrate of CYP3A5 and propose to build a selective CYP3A5 assay capable of quantifying CYP3A5 activity and inhibition in hepatic microsomal incubations. PUBLIC HEALTH RELEVANCE: The cytochrome P450 3A family of enzymes metabolize approximately 50% of pharmaceutical drugs. Unfortunately the activities of the two major human CYP3A enzymes, CYP3A4 and CYP3A5, cannot be differentiated. We propose to develop the first selective CYP3A5 assay using a novel highly selective substrate discovered in our laboratory.

描述（由申请人提供）：人们普遍认为，当其中一种药物干扰参与药物代谢的关键酶（主要是细胞色素 P450 家族中的酶）的活性时，服用多种药物的患者容易受到药代动力学药物相互作用的影响。在过去的十年中，FDA 通常要求公司进行临床试验以确定此类药物相互作用的结果。一些药物如酮康唑已被证明可以抑制单个 P450 酶的活性；而其他药物，如利福平或奥美拉唑，会诱导肝脏中更高水平的 P450 表达。这些相互作用可能需要调整剂量，以避免药物浓度升高和潜在增加的毒性或药物浓度不足而无法发挥作用。现有的体外工具可以合理地预测可能引起大多数常见的基于代谢的药物间相互作用的化合物。然而，目前还没有工具可以区分主要的 CYP3A 酶 CYP3A4 和 CYP3A5。与任何其他 P450 相比，这两种酶参与更多药物的代谢。 CYP3A4/5 活性的改变可能会产生严重后果，通过该途径代谢的药物通常会附带警告：不要与葡萄柚汁、酮康唑、圣约翰疣和许多其他 CYP3A 抑制剂或诱导剂一起服用。 CYP3A5 可能是处方药代谢存在个体间和种族间差异的最重要的遗传因素。至少具有一个活性 CYP3A5*1 等位基因基因的个体表达大量功能性 CYP3A5，而 CYP3A5*3*3 会产生剪接变异，从而导致 CYP3A5 表达最小化。大约 60% 的非裔美国人和 30% 的白种人至少有一个 *1 等位基因，并表达大致相当的 CYP3A5 和 CYP3A4 水平。在生物相关样品中无法清楚地区分 CYP3A4 和 CYP3A5 活性。目前，几乎所有已批准化合物的 CYP3A 抑制数据都是使用 CYP3A 测定生成的，该测定通过汇集的人肝微粒体测量睾酮羟基化或咪达唑仑羟基化。虽然这两种底物均由 CYP3A4 和 CYP3A5 代谢，但所得抑制常数主要反映 CYP3A4，因为肝微粒体的多个供体池中 CYP3A4 的含量大约是 CYP3A5 的五到六倍。我们已经确定了第一个高度选择性的 CYP3A5 底物，并建议建立一种选择性 CYP3A5 检测方法，能够量化肝微粒体孵化中 CYP3A5 的活性和抑制作用。 公共卫生相关性：细胞色素 P450 3A 酶家族代谢大约 50% 的药物。不幸的是，两种主要的人类 CYP3A 酶 CYP3A4 和 CYP3A5 的活性无法区分。我们建议使用我们实验室发现的新型高选择性底物开发第一个选择性 CYP3A5 测定法。