Prediction of Pharmacokinetics and Efficacy/Toxicity by Genotypes of Metabolic Enzymes

已知n -乙酰转移酶2 （NAT2）和细胞色素P450 2C19酶表现出遗传决定的多态性。在DNA水平上对这些酶的遗传变异进行表征，使确定个体基因型成为可能。常用的方法是使用血液样本的聚合酶链反应（PCR）和限制性片段长度多态性（RFLP）方法。我们开发了一种利用单根毛发、颊细胞和指甲提取的基因组DNA来测定NAT2和CYP2C19基因型的新方法。在健康志愿者的研究中，普鲁卡因胺、异烟肼（INH）和磺胺吡啶（SP）的n -乙酰化活性与NAT2基因型密切相关。结核患者尿AcINH和INH比值以及溃疡性结肠炎患者血浆AcSP和SP浓度在各NAT2基因型中也显示出与正常人相同的值。因此，与共给药或肝肾功能相比，NAT2基因型是影响这些药物代谢的主要因素。此外，我们首次发现奥美拉唑抗幽门螺杆菌的疗效可能与CYP2C19基因型有关，即奥美拉唑联合阿莫西林对CYP2C19代谢不良者的根除效果非常好，提示该组在一线治疗时无需使用克拉霉素或甲硝唑。PCR-RFLP基因分型是一种简单的体外试验方法，为根据个体基因型选择最佳治疗方案提供了一种新的策略。

N-acetyltransferase 2 (NAT2) and cytochrome P450 2C19 enzymes are known to exhibit a hereditarily determined polymorphism. The characterization of genetic variation at the DNA level for these enzymes has made it possible to determine an individual genotype. The common method is a polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) method using blood samples. We have developed a novel method for determining the NAT2 and CYP2C19 genotypes using genomic DNA extracted from single hairs, buccal cells and fingernail.The N-acetylation activity for procainamide, isoniazid (INH) and sulfapyridine (SP) was well correlated with NAT2 genotype in healthy volunteers study. Urinary excretion ratios of AcINH and INH in tuberculous patients and plasma concentration of AcSP and SP in ulcreative colitis also showed the same values in each NAT2 genotype as normal subjects. Therefore, NAT2 genotype is the main factor which effect on the metabolism of these drugs compared with coadministration drugs or hepatic and renal functions. Furthermore, we have first found that anti-Helicobacter pylori efficacy of omeprazole can be related to the CYP2C19 genotype, that is, the eradication effect of omeprazole with amoxicillin was highly efficient in CYP2C19 poor metabolizers, suggesting that clarithromycin or metronidazole needs not to be used for this group on the first line therapy. Genotyping by PCR-RFLP,which is a simple in vitro test, can provide a new strategy to choose an optimal regimen based upon the individual genotype.