用体外代谢数据预测临床上药物体内代谢性相互作用

用体外代谢数据可以预测临床上药物体内代谢的相互作用。本文介绍其中一些重要概念、预测模型、方法及影响预测准确性的因素。     

Molecular Aspects of Drug Metabolism

Abstract: Drug oxidation is linked to a liver-microsomal electron transport system consisting of at least two components - cytochrome P-450 and the NADPH-cytochrome P-450 reductase. Cytochrome P-450 is also involved in the hydroxylation of lipid-soluble endogenous compounds, such as steroid hormones and fatty acids. Substrates capable of undergoing hydroxylation bind to cytochrome P-450 and the reduction of the cytochrome P-450-substrate complex so formed may well be the rate-limiting step in the over-all hydroxylation process. It is suggested that the competitive inhibition that various substrates exert on each other's hydroxylation is due to a competition for binding to a common cytochrome P-450 species in the liver microsomes.     

六种大鼠肝微粒体细胞色素P450重组酶系对33种外来化合物的代谢

多氯联苯诱导的六种鼠肝微粒体细胞色素P450重组酶系A_1,A_2,B,C_1,C_2和D对33种外来化合物代谢的催化速率不同,其中以C_1酶系和C_2酶系催化活力最强,其次为A_1酶系,B酶系催化活力最弱,外来化合物的种类不同,经重组酶系催化的途径也不同,如卤代烷烃,卤代烯烃,苯及其同系物,亚硝胺类等化合物主要经P450C_1酶系代谢,而大多数有机磷酸酯,氨基甲酸酯类化合物及多环芳烃类致癌物则以P450 C_2酶系代谢为主。     

Metabolism of 4-Aminopiperidine Drugs by Cytochrome P450s: Molecular and Quantum Mechanical Insights into Drug Design

4-Aminopiperidines are a variety of therapeutic agents that are extensively metabolized by cytochrome P450s with CYP3A4 as a major isoform catalyzing their N-dealkylation reaction. However, its catalytic mechanism has not been fully elucidated in a molecular interaction level. Here, we applied theoretical approaches including the molecular mechanics-based docking to study the binding patterns and quantum mechanics-based reactivity calculations. They were supported by the experimental human liver microsomal clearance and P450 isoform phenotyping data. Our results herein suggested that the molecular interactions between substrates and CYP3A4 active site residues are essential for the N-dealkylation of 4-aminopiperidines. We also found that the serine 119 residue of CYP3A4 may serve as a key hydrogen-bonding partner to interact with the 4-amino groups of the studied drugs. The reactivity of the side chain α-carbon hydrogens drives the direction of catalysis as well. As a result, structure-based drug design approaches look promising to guide drug discovery programs into the optimized drug metabolism space.     

Drug Metabolism Activities of Isolated Rat Hepatocytes in Monolayer Culture

Abstract: The levels of cytochrome P-450 in hepatocytes cultured as monolayers for 22 hrs in Dulbecco's modified Eagle medium supplemented with serum and insulin was reduced to approximately 40% of initial values of freshly isolated hepatocytes. In correspondance with this the activities of the cytochrome P-450 monooxygenases aryl hydrocarbon (benzo(a)pyrene) hydroxylase (AHH) and ethylmorphine (EM) N-demethylase were reduced to 40 and 22% of their initial activities, respectively. Modifying the culture medium through omission of cysteine and cystine, and adding dexamethazone and delta-amino levulinic acid, increased the content of cytochrome P-450 to 59 % and EM N-demethylase to 46 % of initial values, but was without effect on AHH activity. However, further modifications by adding high concentrations of asparagine and leucine increased AHH activity to 62% of initial values, but did not further enhance the total content of cytochrome P-450 or the EM N-demethylase activity. The activities of cytochrome P-450 reductase, flavin containing monooxygenase, epoxide hydrolase and glutathione S-transferase decreased less (to about 70–80% of initial values) than cytochrome P-450 associated monooxygenase activities, whereas UDP-glucuronyl transferase decreased to about 50% of initial values. In contrast to what was observed regarding cytochrome P-450 and associated monooxygenase activities, modification of the incubation conditions did not affect the non-cytochrome P-450 enzymatic activities.     

精神科住院患者医嘱中CYP450介导的药物相互作用风险分析

目的 调查河北医科大学第一医院精神科住院患者存在细胞色素P450酶（CYP450）介导的药物相互作用的住院医嘱,分析潜在具有临床意义的药物相互作用,为临床用药提供参考。方法 对河北医科大学第一医院2018年7月1日-12月31日精神科住院患者所有运行病历的用药情况进行统计分析,筛选联用≥ 2种药物的医嘱,记录联合用药中含有CYP450酶底物、抑制剂或诱导剂的情况。以代谢酶学理论为指导,以药品说明书、相关文献报道为基础,评价医嘱中潜在的代谢性药物相互作用,并统计临床发生实际药物相互作用的病例。结果 共查阅1 658份病历,其中存在代谢性药物相互作用的病历227份,占13.7%,涉及的CYP酶的亚型主要有CYP2D6（n=176,77.5%）、CYP3A4（n=105,46.3%）、CYP2C19（n=24,10.6%）和CYP2C9（n=5,2.2%）。临床发生实际药物相互作用的病历6份,占2.6%。结论 河北医科大学第一医院精神科住院患者病历中存在潜在的代谢性药物相互作用较多。为提高用药的疗效与安全,临床上应尽量避免联用已有文献报道的存在不良相互作用的药物,选择没有相互作用或相互作用较少的同类药物。     

Drug Metabolism within the Brain Changes Drug Response: Selective Manipulation of Brain CYP2B Alters Propofol Effects

Drug-metabolizing cytochrome P450 (CYPs) enzymes are expressed in the liver, as well as in extrahepatic tissues such as the brain. Here we show for the first time that drug metabolism by a CYP within the brain, illustrated using CYP2B and the anesthetic propofol (2, 6-diisopropylphenol, Diprivan), can meaningfully alter the pharmacological response to a CNS acting drug. CYP2B is expressed in the brains of animals and humans, and this CYP isoform is able to metabolize centrally acting substrates such as propofol, ecstasy, and serotonin. Rats were given intracerebroventricularly (i.c.v.) injections of vehicle, C8-xanthate, or 8-methoxypsoralen (CYP2B mechanism-based inhibitors) and then tested for sleep time following propofol (80 mg/kg intraperitoneally). Both inhibitors significantly increased sleep-time (1.8- to 2-fold) and brain propofol levels, while having no effect on plasma propofol levels. Seven days of nicotine treatment can induce the expression of brain, but not hepatic, CYP2B, and this induction reduced propofol sleep times by 2.5-fold. This reduction was reversed in a dose-dependent manner by i.c.v. injections of inhibitor. Sleep times correlated with brain (r=0.76, P=0.0009), but not plasma (r=0.24, P=0.39) propofol concentrations. Inhibitor treatments increased brain, but not plasma, propofol levels, and had no effect on hepatic enzyme activity. These data indicate that brain CYP2B can metabolize neuroactive substrates (eg, propofol) and can alter their pharmacological response. This has wider implications for localized CYP-mediated metabolism of drugs, neurotransmitters, and neurotoxins within the brain by this highly variable enzyme family and other CYP subfamilies expressed in the brain.     

介导候选药代谢的肝细胞色素P450酶表型鉴定的定性和定量方法

新药研发需要对候选药物的代谢途径、每个代谢途径对总清除率的贡献以及参与代谢的酶进行详细研究。候选药物经过肝细胞色素P450(CYP)酶代谢的比例(f_m)可以用放射性同位素标记的方法在人体水平测定,而肝中某酶亚型的代谢占总的CYP参与代谢的比例(f_CYPi)可以用体外酶表型鉴定的方法来测定,这两个参数的乘积f_m×f_CYPi即为某个CYP酶亚型代谢参与某候选药物体内清除的百分比,对研究体内药物-药物相互作用具有重要意义。本文从定性和定量两方面综述体外酶表型鉴定的研究方法。     

Drug Metabolism in the Nasal Mucosa

Nasal delivery is a potential alternative for systemic availability of drugs restricted to intravenous administration, such as peptide and protein drugs. Although nasal delivery avoids the hepatic first-pass effect, the enzymatic barrier of the nasal mucosa creates a pseudo-first-pass effect. The xenobiotic metabolic activity in the nasal epithelium has been investigated in several species including humans. The Phase I, cytochrome P-450 enzymes have been studied extensively for their toxicological significance, since these enzymes metabolize inhaled pollutants into reactive metabolites which may induce nasal tumors. The cytochrome P-450 activity in the olfactory region of the nasal epithelium is higher even than in the liver, mainly because of a three- to fourfold higher NADPH–cytochrome P-450 reductase content. Phase II activity has also been found in the nasal epithelium. The delivery of peptides and proteins has been hindered by the peptidase and protease activity in the nasal mucosa. The predominant enzyme appears to be aminopeptidase among other exopeptidases and endopeptidases. The absorption of peptide drugs can be improved by using aminoboronic acid derivatives, amastatin, and other enzyme inhibitors as absorption enhancers. It is possible that some of the surfactants, e.g., bile salts, increase absorption by inhibiting the proteolytic enzymes. Thus, in addition to the permeation barriers, there also exists an enzymatic barrier to nasal drug delivery, which is created by metabolic enzymes in the nasal epithelium.     

Reaction Phenotyping: Current Industry Efforts to Identify Enzymes Responsible for Metabolizing Drug Candidates

Reaction phenotyping studies to identify specific enzymes involved in the metabolism of drug candidates are increasingly important in drug discovery efforts. Experimental approaches used for CYP reaction phenotyping include incubations with cDNA expressed CYP enzyme systems and incubations containing specific CYP enzyme inhibitors. Since both types of experiments present specific advantages as well as known drawbacks, these studies are generally viewed as complementary approaches. Although glucuronidation pathways are also known to present potential drug-drug interaction issues as well as challenges related to their polymorphic expression, reaction phenotyping approaches for glucuronidation are generally limited to cDNA expressed systems due to lack of availability of specific UGT inhibitors. This article presents a limited review of current approaches to reaction phenotyping studies used within the pharmaceutical industry.     

新型抗抑郁药的代谢与细胞色素P450介导的药物相互作用

新型抗抑郁药(选择性5-羟色胺再摄取抑制剂,SSRI)疗效肯定,耐受性好,已得到广泛应用。SSRI剂既是P 450酶的底物又是P 450酶的抑制剂,其重要特征是对P 450酶的抑制。当SSRI剂与P 450酶的其他底物合用时,可能发生明显的具有临床意义的药物相互作用。     

基于片段的药物设计研究进展

基于片段的药物设计（FBDD）方法是一种通过筛选碎片库得到苗头片段,然后采用基于结构的设计策略对苗头片段进行优化和改造获得先导化合物的研究。其研究过程分为3个部分：1）设计并构建片段库;2）片段库的筛选;3）利用基于结构的药物设计策略对苗头片段进行优化设计,最终得到类药性的先导化合物或候选化合物。通过结合已经上市的3个抗肿瘤药物（vemurafenib,venetoclax和erdafitinib）和KRAS^G12C抑制剂AMG510的研究为实例对FBDD的最新研究进展进行综述。     

The Effect of RPR 102341 on Theophylline Metabolism and Phenacetin O-Deethylase Activity in Human Liver Microsomes

Purpose. RPR 102341 is structurally similar to the fluoroquinolone class of antibiotics. Because some fluoroquinolones have been shown to inhibit theophylline metabolism, concomitant administration may increase plasma levels of theophylline resulting in serious adverse effects. The purpose of this study was to determine if RPR 102341 affects theophylline metabolism in vitro and, thus, predict whether a clinically significant drug interaction is likely to occur. In addition, the effect of RPR 102341 on phenacetin O-deethylase activity was determined to address the enzymatic basis of a potential drug interaction. Methods. The in vitro theophylline metabolism assay was conducted according to a modification of a published procedure. The phenacetin O-deethylase assay was conducted according to a modification of a published procedure. Results. The rate of conversion of theophylline to 3-methylxanthine in human liver microsomes in the presence of 100 M and 500 M RPR 102341 was 93.6 and 106 percent of the control reactions, respectively. The formation of 1-methylxanthine was 97.6 and 100 percent of the control, and 1,3-dimethyluric acid formation was 88.9 and 95.2 percent of control at 100 M and 500 M RPR 102341, respectively. In agreement, RPR 102341 caused no inhibition of human liver CYP1A2—catalyzed phenacetin O-deethylase activity. Finally, no inhibition was observed when RPR 102341 was incubated with human liver microsomes and an NADPH regenerating system prior to the addition of theophylline. Conclusions. Based on these studies, RPR 102341 is not expected to cause significant drug interactions with theophylline.     

细胞色素P450酶基因多态性的研究进展及临床意义

细胞色素P450（cytochrome P450,CYP）是重要的药物代谢酶,参与催化多种内源和外源化合物,特别是多种临床药物的生物转化。CYP存在广泛的基因多态性和表型多态性,体现在个体对于各种化合物的代谢存在明显差异。本文综述了CYP的基因多态性、与药物代谢相关的CYP各亚型的特点和临床意义,主要目的是合理解释和预测临床上药物间相互作用和药物不良反应等,为实现临床个体化给药提供科学依据。     

抗心绞痛药的药物相互作用

心绞痛是常见的心血管疾病。临床常用的抗心绞痛药易发生药物之间的相互作用。本文综述了与常用抗心绞痛药物相关的药动学方面的相互作用研究进展,为临床用药提供参考。     

取代苯胺与细胞色素P450相互作用时的结构与活性关系

本研究用不同来源的鼠肝微粒体,测定了40余种取代苯胺生成细胞色素P450代谢中问体(MI)络合物的能力,其结构与活性间关系可归纳如下:(1)在氨基的对位或间位必须存在一个可提供孤对电子的取代基,当此取代基位于邻位时,化合物不能生成P450-MI络合物,(2)在对位取代基中除了可提供孤对电子的基团外,引入亲脂性结构有助于生成P450-MI络合物,(3)间氯或对-氯邻甲苯胺似仅选择性地络合苯巴比妥与Aroclor共诱导的P450亚族,(4)苯环上若无可提供孤对电子的基团,任何疏水性,亲水性或供电子取代基均无助于取代苯胺生成P450-MI络合物。(5)一组可形成P450-MI络合物的取代苯胺(取代对氨基二苯醚)延长小鼠戊巴比妥睡眠时间的能力与取代基的电性相关。     

细胞色素P450酶与药物代谢的研究进展与评价

目的：评价细胞色素P450酶与药物代谢的研究进展,以供临床医师合理用药参考。方法：查阅近年来国内、外的相关文献资料,进行归纳和分析。结果与结论：肝细胞色素P450酶系参与人体许多内、外源性物质（包括药物）的分解和代谢。P450酶系在体内的分布、结构和功能在药物代谢和临床疾病诊断过程中有着十分重要的药理作用和临床意义。     

Approaching Target Selectivity by De Novo Drug Design

ABSTRACT

Introduction: The development of drug candidates with a defined selectivity profile and a unique molecular structure is of fundamental interest for drug discovery. In contrast to the costly screening of large substance libraries, the targeted de novo design of a drug by using structural information of either the biological target and/or structure–activity relationship data of active modulators offers an efficient and intellectually appealing alternative.

Areas covered: This review provides an overview on the different techniques of de novo drug design (ligand-based drug design, structure-based drug design, and fragment-based drug design) and highlights successful examples of this targeted approach toward selective modulators of therapeutically relevant targets.

Expert opinion: De novo drug design has established itself as a very efficient method for the development of potent and selective modulators for a variety of different biological target classes. The ever-growing wealth of structural data on therapeutic targets will certainly further enhance the importance of de novo design for the drug discovery process in the future. However, a consistent use of the terminology of de novo drug design in the scientific literature should be sought.