基于PBPK建模的早产儿CYP1A2酶活性研究

While the adverse drug reactions are commonly seen in premature infants, the developmental changes of one important drug metabolizing enzyme, cytochrome P450 1A2 (CYP1A2), in premature infants still remains unclear. Furthermore, data collected from premature infants by using conventional pharmacokinetic methods cannot be ethically and practically applied in this population. Physiologically based pharmacokinetics (PBPK) modeling is a mathematical modeling technique which can be used for predicting the drug dosage and organs exposure in premature infants. However, this model is usually built based on the studies from the animal and in vitro models, or the extrapolated data gathered from adults or older children. The developing activity of drug metabolizing enzyme, blood flow rate and volume of the vital organs in premature infants are actually very important data for PBPK simulation. The current problem is that these data are extremely rare. For these reasons, the result from PBPK simulation is not so reliable. In this study, spare blood sample from premature infants who were treated with caffeine, the only CYP1A2 probe substrate in human, will be collected and the concentration of caffeine and its metabolites paraxanthine (1,7-dimethylxanthine) in the blood will be measured with ultra-performance liquid chromatography massspectrometry (UPLC-MS) method. Then the data will be analyzed by using non-linear mixed-effects model (NONMEM) to illuminate the rules of developmental changes of CYP1A2 enzyme activity in premature infants from 0 to 3 months (adjusted gestational age is about 40 weeks) . The study will also assess the influence of gene polymorphisms on enzyme activity. Furthermore, the developmental changes of blood flow and volume in main organs including lung, kidney, heart, and brain will be detected by using a noninvasive Doppler imaging and three - dimensional ultrasound technology . These data, collected from the premature infants, will finally replace the estimate data or data still lacked in PBPK. After that, the accuracy of PBPK simulation will be evaluated through importing the concentration data of CYP1A2 substrates. The current study will increase the accuracy of PBPK simulation for preterm infants in clinical trial and will enable more accurate dose selection.

早产儿药物不良反应率高，CYP1A2酶活性变化规律尚未知，通过传统药动学研究方法获得安全用药资料伦理和操作上不可行。国际上正推行使用生理药动学（PBPK）模型预测早产儿用药剂量和器官暴露，但基础数据多来自动物、体外或基于年龄估算，用于准确建模的早产儿重要器官血流、体积及酶活性数据奇缺，模型容易产生偏倚。本研究拟在前期工作基础上，利用临床进行咖啡因（CYP1A2体内探针底物）治疗的早产儿剩余血样，通过咖啡因和其代谢物浓度，利用非线性混合效应模型法阐明0-3月龄（校正胎龄40周）CYP1A2酶活性变化规律以及基因多态性对酶活性的影响，并应用无创的二维多普勒和三维超声技术明确0-3月龄早产儿肝、肾、心、脑血流速率和体积变化规律，然后将获得的数据替代PBPK软件中稀缺或基于年龄估算的数据，考察CYP1A2底物PBPK建模的准确性。本研究对于提高早产儿PBPK临床给药方案设计和风险评估具有重要意义。

早产儿药物不良反应率高，CYP1A2酶活性变化规律尚未知，通过传统药动学研究方法获得安全用药资料伦理和操作上不可行。本研究采用机会采血法，采集临床进行咖啡因（CYP1A2体内探针底物）治疗的早产儿剩余血样，建立测定咖啡因和其代谢物浓度的方法，利用非线性混合效应模型法建立早产儿咖啡因群体药代动力学模型；研究早产新生儿CYP1A2酶活性变化规律以及基因多态性对酶活性的影响，并应用无创的二维多普勒和三维超声技术明确0-3月龄早产儿肝、肾、心、脑血流速率变化规律。本研究建立了能够同时对咖啡因及其三种初级代谢产物进行含量测定的方法，实现对早产儿剩余血样中4个指标成分高精度、高灵敏度、快速的定量。本研究通过考察多种生理病理、CYP1A2基因型等因素，以当日体重 (CW)、矫正胎龄 (PMA)、 血清肌酐浓度(CREA)作为清除率 (CL)的协变量，将CW作为（表观分布容积）Vd的协变量建立建立咖啡因早产儿群体药代动力学模型。本研究利用咖啡因和其三个代谢产物的浓度对早产儿的CYP1A2活性进行分析，发现CYP1A2酶活性与出生体重（BW）、出生后年龄（PNA）、CW成正相关，与CREA呈负相关。此外，CYP1A2酶活性与 PMA和ALT成正相关。CW和CYP1A2*1C基因型影响CYT1A2活性。基因型CYP1A2*1C和CYP1A2*1D影响了咖啡因的去甲基化过程。分析发现1-3月早产儿头颅大脑中动脉峰值流速有逐渐增高的趋势，阻力指数缓慢增高，肝脏门静脉峰值流速未见明显差异，心脏主动脉及肺动脉峰值流速未见明显差异。本研究获得的数据可用于补充PBPK软件中稀缺或基于年龄估算的数据，提高CYP1A2底物PBPK建模的准确性。本研究对于提高早产儿临床给药方案设计和风险评估具有意义。