Prediction of drug-drug interaction risk of P-glycoprotein substrate in drug discovery

We aimed to predict the drug-drug interaction (DDI) risk of P-glycoprotein (P-gp) substrates by using P-gp expressing LLC-PK1 cells and its knockout mice (KO). The area under the curve (AUC) of 16 marketed drugs and plasma concentration (Cplasma) of 207 screening compounds, with corrected efflux ratio (CER) ≥ 2, were compared between P-gp KO mice and wild type mice (WT). At permeability (Papp) ≥ 10 × 10−6 cm/sec in parent LLC-PK1 cells, AUC ratios (KO/WT) and Cplasma ratios (KO/WT) of these compounds were within 3-fold. Besides, AUC ratios (KO/WT) of clinical P-gp substrates, with human AUC ratio with and without P-gp inhibitor administration ≥2, were found to be higher than 8.7. Based on these observations of Papp and AUC ratios, we established a work-flow of P-gp substrate assessment with the threshold, AUC ratio (KO/WT) ≥ 9 leading to DDI risk of AUC ratio (human) ≥ 2. Subsequently, the screening compound showing high CER (=57.6), but its AUC ratio (KO/WT) was 3.7, had been presumed to be weak risk and its AUC ratio (human) was 1.2 at later clinical DDI study. Proposed workflow should be useful for predicting the DDI risk of P-gp substrates in drug discovery.