Quantiative prediction of intestinal availability of CYP3A4 substrates

通过人肠道微粒体体外代谢研究和Caco-2细胞外排研究，定量预测CYP3A4底物的肠可利用性（Fg）。以阿普唑仑（ALP）、三唑仑（TRZ）、咪达唑仑（MDZ）、卡马西平（CBZ）和睾酮（TST）作为模型CYP3A4底物。根据单室动力学模型预测Fg值，并建立了更精确的模型，包括药物在肠腔内的转运、肠上皮细胞的吸收、上皮细胞的代谢和进入门静脉的出口：肠转运、吸收和代谢（ITAM）模型。根据单室动力学模型可以很好地预测ALP、TRZ和CBZ的Fg值。然而，MDZ的预测Fg小于已报道的人体Fg。由于已有报道称MDZ在CYP3A4表达系统中表现出基于机制的抑制剂样特征，因此我们研究MDZ在人肠微粒体中是否表现出基于机制的抑制剂样特征。MDZ在人肠道微粒体中确实表现出基于机制的抑制剂样特征，并且使用具有基于机制的抑制剂样特征的ITAM模型预测MDZ的Fg。MDZ的预测Fg值与报道值接近，说明MDZ在上皮细胞中是一种基于机制的抑制剂，在吸收过程中MDZ本身的代谢受到抑制。

Intestinal availability (Fg) of CYP3A4 substrates were quantitatively predicted based on the in vitro metabolic study with human intestinal microsomes and the efflux study with Caco-2 cells. Alprazolm (ALP), triazolam (TRZ), midazolam (MDZ), carbamazepine (CBZ) and testosterone (TST) were used as model CYP3A4 substrates. Fg values were predicted according to the single compartment kinetic model, and the more precise model was also developed which incorporated the transit of the drug in the intestinal lumen, absorption into the intestinal epithelial cells, the metabolism in the epithelial cells and the exit to the portal vein: Intestinal Transit, Absorption and Metabolism (ITAM) model.Fg values of ALP, TRZ and CBZ were well predicted according to the single compartment kinetic model. However, the predicted Fg of MDZ was smaller than the reported Fg in humans. Since it has been reported that MDZ shows mechanism-based inhibitor like characteristics in CYP3A4 expression system, we studied if MDZ exhibits mechanism-based inhibitor like characteristics in human intestinal microsomes. MDZ did exhibit mechanism-based inhibitor like characteristics in human intestinal microsomes, and the Fg of MDZ was predicted using an ITAM model with mechanism based inhibitor like characteristics. The predicted Fg value of MDZ became close to the reported value, which indicated that MDZ acts as a mechanism-based inhibitor in the epithelial cells and that the metabolism of MDZ itself is inhibited in the process of absorption.