Ontogeny of Drug Bioactivation and Idiosyncratic ADRs

描述（由申请人提供）：特异性药物不良反应（adr）相对罕见，但可能危及生命的事件，其中易感性的决定因素（很大程度上未知）被认为是经历不良事件的个体所特有的。它们可以发生在整个年龄谱中，但在儿科文献中往往被低估，然而儿童似乎面临某些特殊adr的风险增加，如丙戊酸肝毒性和拉莫三嗪的皮肤反应。特殊不良反应发生的一个重要步骤似乎是相关药物的生物转化为化学反应性代谢物（“生物活化”），这种代谢物能够与细胞大分子结合，并通过启动免疫反应直接或间接地产生细胞死亡。虽然药物代谢酶如细胞色素P450 （CYPs）和葡萄糖醛基转移酶（UGTs）的发育变化已经在儿童中得到了表征，但对儿童生长发育过程中药物生物活化的个体发生机制知之甚少。利用对乙酰氨基酚（APAP）、卡马西平（CBZ）和丙戊酸（VPA）的生物活性（和解毒）生物标志物，本研究计划的目标是：1。2.探讨药物生物活化标志物在体内和体外的发生机制。确定生长发育过程中APAP、CBZ和VPA生物标志物表达个体间差异的药理学决定因素。为了实现这些目标，将进行两项纵向“生物激活”表型研究。健康儿童接受单次试验剂量APAP （15 mg/kg作为泰诺(r)无酒精溶液，80mg/0.8ml）和2。在密苏里州堪萨斯城、洛杉矶什里夫波特和AR小石城的癫痫儿童中，常规接受CBZ或VPA治疗涉及NICHD PPRU部位的疾病。在每项研究中，收集夜间尿液并分析母体药物、“无毒”代谢物和候选反应性代谢物的偶联代谢物的存在。特定的尿代谢物比率将用于确定生长发育过程中发生的反应性代谢“负担”的变化，具体参考目前正在进行的纵向表型研究中确定的CYP活性的变化。来自极端人群分布的成对DNA样本将通过DNA测序和片段分析进行协同搜索，以寻找导致药物生物活性个体间差异的单核苷酸多态性（snp）。预计该项目的结果将允许增加生物活性的关键时期，从而确定特异性adr的潜在易感性，以用于后续的前瞻性研究。

DESCRIPTION (provided by applicant): Idiosyncratic adverse drug reactions (ADRs) are relatively rare, but potentially life-threatening events in which the determinants of susceptibility (largely unknown) are thought to be unique to the individual experiencing the adverse event. They can occur throughout the age spectrum but tend to be underemphasized in the pediatric literature yet children appear to be at increased risk for certain idiosyncratic ADRs such as valproate hepatotoxicity and cutaneous reactions to lamotrigine. An important step in the development of an idiosyncratic ADR appears to be biotransformation of the implicated drug to a chemically reactive metabolite ("bioactivation") that is capable of binding to cellular macromolecules and producing cell death directly or indirectly through initiation of an immune response. Although developmental changes in drug metabolizing enzymes such as the cytochromes P450 (CYPs) and glucuronosyl transferase (UGTs) have been characterized in children, little is known about the ontogeny of drug bioactivation as children grow and develop. Using biomarkers of acetaminophen (APAP), carbamazepine (CBZ) and valproic acid (VPA) bioactivation (and detoxification) in vivo, the goals of this research program are 1. to characterize the ontogeny of the drug bioactivation biomarkers in vivo and in vitro and 2. to identify the pharmacogenetic determinants of interindividual variability in APAP, CBZ and VPA biomarker expression during growth and development. To achieve these goals, two longitudinal "bioactivation" phenotyping studies will be conducted 1. in healthy children following a single test dose of APAP (15 mg/kg as Tylenol(r) alcohol-free solution, 80mg/0.8ml) and 2. in epileptic children routinely receiving CBZ or VPA for medical management of their disease involving NICHD PPRU sites in Kansas City, MO, Shreveport, LA, and Little Rock, AR. For each study, urine is collected overnight and analyzed for the presence of parent drug, "non-toxic" metabolites and conjugated l metabolites of candidate reactive metabolites. Specific urinary metabolite ratios will be used to determine the changes in reactive metabolic "burden" that occur during growth and development with specific reference to changes in CYP activities identified in longitudinal phenotyping studies currently underway. Paired DNA samples from the extremes of the population distributions will be subjected to a concerted search by DNA sequencing and fragment analysis for single nucleotide polymorphisms (SNPs) that contribute to inter-individual variability in drug bioactivation. It is anticipated that the results of this program will allow critical periods of increased bioactivation and thus, potential vulnerability to idiosyncratic ADRs, to be identified for subsequent prospective investigations.