PREDICTION OF DRUG INTERACTIONS IN VIVO AND IN VITRO

这项提案的总体目标是评估一个新的框架 基于药物相互作用的抑制预测。这个框架是 基于表征抑制剂对其影响的能力 人肝微粒体中特异性细胞色素P450亚型的研究 准备工作。将检验两个假设：假设1： 任何药物-抑制剂在体内相互作用的机制都可以解释 从(I)特定细胞色素P450亚型的测定 负责该药物的主要代谢途径和(Ii)a 每种异构体体外抑制物KI的测定。假设 2：对于任何药物-抑制剂在体内的相互作用，米氏-曼顿 模型可以用来计算体内特异性的异构体抑制 常量(基辅)。该常量提供了对 预计在该抑制剂和任何 底物。 这些假说将用两类药物进行评估， 基于抑制的相互作用构成了一个关键的临床现实。 将实现以下具体目标：1(A)确定、使用 人肝微粒体，如果华法林和华法林的临床相互作用 13种常用的处方药是由于抑制 细胞色素P450 2 C9。1(B)使用人类肝脏微粒子来确定临床上是否 4种主要抗惊厥药物与33种其他药物的相互作用 抑制负责的特定异构体的后果 抗惊厥药的主要清除量。如果是这样的话， 测定体外KI对这些异构体的抑制作用 将这些值与基辅的相应估计值进行比较 文献资料。2(A)就亚型CYP2C9而言，证明(I) (S)-华法林与氟康唑的相互作用程度可达 通过比率I/Kiv进行定量预测，其中I是血浆 缓蚀剂浓度和(Ii)对于2C9获得相同的Kiv 以苯妥英钠为底物时的氟康唑。2(B)至 对于异构型3A4，证明(I)相互作用的程度 (R)-华法林和氟康唑可通过以下方法定量预测 比率I/KiIV和(Ii)对于3A4氟康唑得到相同的KiIV 以卡马西平为底物时。2(C)以证明 具体目标2(A)和2(B)的方法是非依赖于抑制剂的，a 对于每种同工酶，将使用相同的底物使用第二种抑制剂。 实验方法包括使用人类肝库，可靠 分析技术和一些健康受试者的人体研究。 如果提出的假设得到验证，就有可能 预测任何新药的基于抑制的相互作用。

The overall objective of this proposal is to evaluate a new framework for the prediction of inhibition based drug interactions. This framework is based on the ability to characterize the effects of inhibitors on specific cytochrome P450 isoforms using human liver microsomal preparations. Two hypotheses will be tested: Hypothesis 1: The mechanism of any drug-inhibitor in vivo interaction can be accounted for from (i) a determination of the specific cytochrome P450 isoforms responsible for that drug's major route of metabolism and (ii) a measurement of the inhibitor in vitro Ki for each isoform. Hypothesis 2: For any drug-inhibitor in vivo interaction, the Michaelis-Menton model can be used to calculate an isoform specific in vivo inhibition constant (Kiiv). This constant provides a quantitative estimate of the magnitude of interaction to be expected between that inhibitor and any substrate. These hypotheses will be evaluated with two classes of drugs for which inhibition based interactions constitute a critical clinical reality. The following Specific Aims will be pursued: 1(a) To determine, using human liver microsomes, if the clinical interactions between warfarin and 13 commonly prescribed drugs are a consequence of the inhibition of CYP2C9. 1(b) To determine, using human liver microsomes, if the clinical interactions between 4 major anticonvulsants and 33 other drugs are a consequence of inhibition of the specific isoforms responsible for the major fractional clearances of the anticonvulsants. If they are, to determine the in vitro Ki's for the inhibition of these isoforms and to compare these values to the corresponding Kiiv's estimated from literature data. 2(a) To demonstrate, for isoform CYP2C9, that (i) the degree of interaction between (S)-warfarin and fluconazole can be predicted quantitatively by the ratio, I/Kiiv, where I is the plasma inhibitor concentration and (ii) the same Kiiv for 2C9 is obtained for fluconazole when phenytoin is used as the substrate. 2(b) To demonstrate, for isoform 3A4, that (i) the degree of interaction between (R)-warfarin and fluconazole can be predicted quantitatively by the ratio, I/Kiiv, and (ii) the same Kiiv for 3A4 is obtained for fluconazole when carbamazepine is used as the substrate. 2(c) To demonstrate that the approach of specific aims 2(a) and 2(b) is inhibitor independent, a second inhibitor will be used with the same substrates for each isozyme. The experimental approaches include the use of human liver bank, reliable analytical techniques and a number of human studies in healthy subjects. If the proposed hypotheses are validated it will become possible to predict inhibition based interactions for any new drug.