Ontogeny of Drug Bioactivation and Idiosyncratic ADRs

描述（由申请方提供）：特异质药物不良反应（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（大部分未知）被认为是发生不良事件的个体所独有的。这些不良反应可发生于整个年龄范围，但在儿科文献中往往未得到充分强调，但儿童发生某些特异质ADR（如丙戊酸盐肝毒性和拉莫三嗪皮肤反应）的风险似乎增加。特异质ADR发展中的一个重要步骤似乎是将涉及的药物生物转化为化学反应性代谢物（“生物活化”），该代谢物能够结合细胞大分子并通过引发免疫应答直接或间接产生细胞死亡。虽然药物代谢酶，如细胞色素P450（CYP）和葡萄糖醛酸转移酶（UGT）的发育变化已在儿童中的特点，很少有人知道的个体发育的药物生物激活儿童的生长和发展。利用生物标记物对乙酰氨基酚（APAP），卡马西平（CBZ）和丙戊酸（VPA）的体内生物活化（和解毒），本研究计划的目标是1。在体内和体外表征药物生物活化生物标志物的个体发育;以及2.确定生长发育期间APAP、CBZ和VPA生物标志物表达个体间变异性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“生物活化”表型研究1。在健康儿童中，在单次测试剂量的APAP（15 mg/kg，作为Tylenol（r）无酒精溶液，80 mg/0.8ml）和2.在常规接受CBZ或VPA进行疾病医学管理的癫痫儿童中，涉及堪萨斯城、密苏里州、洛杉矶什里夫波特和阿肯色州小石城的NICHD PPRU中心。对于每项研究，过夜收集尿液并分析母体药物、“无毒”代谢物和候选反应性代谢物的缀合代谢物的存在。将使用特定的尿代谢物比率来确定生长和发育期间发生的反应性代谢“负荷”的变化，具体参考目前正在进行的纵向表型研究中确定的代谢物活性的变化。来自极端人群分布的配对DNA样本将通过DNA测序和片段分析进行协调一致的搜索，以寻找导致药物生物活化个体间变异性的单核苷酸多态性（SNP）。预计该项目的结果将允许生物活化增加的关键时期，从而确定对特异质ADR的潜在脆弱性，用于后续前瞻性研究。

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.