Ontogeny of Drug Bioactivation and Idiosyncratic ADRs

描述(由申请人提供)：特殊的药物不良反应(ADR)是相对罕见的，但可能危及生命的事件，其中易感性决定因素(基本上未知)被认为是经历不良事件的个人独有的。它们可以发生在整个年龄段，但在儿科文献中往往没有得到足够的重视，但儿童似乎有更高的风险患上某些特殊的不良反应，如丙戊酸盐、肝毒性和对拉莫三嗪的皮肤反应。在一种特殊的ADR的发展中，一个重要的步骤似乎是将所涉及的药物生物转化为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的化学活性代谢物(“生物激活”)。尽管细胞色素P450(Cyps)和葡萄糖醛酸基转移酶(UGTS)等药物代谢酶在儿童中的发育变化已有报道，但对儿童生长发育过程中药物生物激活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)的体内生物激活(和解毒)生物标记物，本研究的目标是1.表征药物生物激活生物标记物在体内和体外的个体发育；2.确定APAP、CBZ和VPA生物标记物在生长发育过程中个体差异的药物遗传学决定因素。为了实现这些目标，将进行两项纵向的“生物激活”表型研究：1.对于单次测试剂量的APAP(15毫克/公斤泰诺(R)无酒精溶液，80毫克/0.8毫升)的健康儿童，以及2.癫痫儿童，常规接受CBZ或VPA进行药物治疗，涉及位于堪萨斯城、密苏里州、什里夫波特、洛杉矶和阿肯色州小石城的NICHD PPRU地点。对于每项研究，彻夜收集尿液，并分析是否存在母药、“无毒”代谢物和候选反应性代谢物的结合L代谢物。特定的尿代谢物比率将被用来确定在生长和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。来自种群分布极端的配对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(SNPs)。预计该计划的结果将使生物活性增加的关键时期得以确定，从而为后续的前瞻性研究确定对特殊ADR的潜在脆弱性。

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.