RT Journal Article SR Electronic T1 Significance of basal membrane permeability of epithelial cells in predicting intestinal drug absorption JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP DMD-AR-2022-000907 DO 10.1124/dmd.122.000907 A1 Aoi Yoshitomo A1 Satoshi Asano A1 Shizuka Hozuki A1 Yuta Tamemoto A1 Yukihiro Shibata A1 Natsumi Hashimoto A1 Keita Takahashi A1 Yoko Sasaki A1 Naoka Ozawa A1 Michiharu Kageyama A1 Takeshi Iijima A1 Yasuhiro Kazuki A1 Hiromi Sato A1 Akihiro Hisaka YR 2022 UL http://dmd.aspetjournals.org/content/early/2022/12/07/dmd.122.000907.abstract AB Drug absorption from the gastro-intestinal tract is often restricted by efflux transport by P-glycoprotein (P-gp) and metabolism by cytochrome P450 (CYP) 3A4. Both localize in the epithelial cells and thus their activities are directly affected by the intracellular drug concentration which should be regulated by the ratio of permeability between apical (A) and basal (B) membranes. In this study, using Caco-2 cells with forced expression of CYP3A4, we assessed the transcellular permeation of A-to-B and B-to-A directions and the efflux from the preloaded cells to the both sides of 12 representative P-gp or CYP3A4 substrate drugs, and obtained the parameters for permeabilities, transport, metabolism, and unbound fraction in the enterocytes (fent) using simultaneous and dynamic model analysis. The membrane permeability ratios for B to A (RBA) and fent varied by 8.8-fold and by more than 3,000-fold, respectively, among the drugs. The RBA values for digoxin, repaglinide, fexofenadine, and atorvastatin were greater than 1.0 (3.44, 2.39, 2.27, and 1.90, respectively) in the presence of a P-gp inhibitor, thus suggesting the potential involvement of transporters in the B membrane. The Km for quinidine for P-gp transport was 0.077 µM for the intracellular unbound concentration. These parameters were used to predict overall intestinal availability (FAFG) by applying an intestinal pharmacokinetic model, ATOM, in which permeability of A and B membranes accounted separately. The model predicted changes in the absorption location for P-gp substrates according to its inhibition, and FAFG values of 10/12 drugs, including quinidine at varying doses, were explained appropriately. Significance Statement Pharmacokinetics has improved predictability by identifying the molecular entities of metabolism and transport, and by using mathematical models to appropriately describe drug concentrations at the locations where they act. However, analyses of intestinal absorption so far have not been able to accurately consider the concentrations in the epithelial cells where P-glycoprotein and CYP3A4 exert effects. In this study, the limitation was removed by measuring the apical and basal membrane permeability separately and then analyzing these values using new appropriate models.