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

We aimed at predicting 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/s in parent LLC-PK1 cells, AUC ratios (KO/WT) and Cplasma ratios (KO/WT) of these compounds were within 3-fold. AUC ratios (KO/WT) of clinical P-gp substrates, with human AUC ratios with and without P-gp inhibitor administration ≥2, were higher than 8.7. These observations led us to establish a work-flow of P-gp substrate assessment with the threshold AUC ratio (KO/WT) ≥ 9 leading to a DDI risk of AUC ratio (human) ≥ 2. A screening compound showing high CER (=57.6) was found, but its AUC ratio (KO/WT) was 3.7, had been presumed to be a weak risk and its AUC ratio (human) was 1.2 in a later clinical DDI study. Our proposed workflow should be useful for predicting the DDI risk of P-gp substrates in drug discovery.

Brain-transportable soy dipeptide, Tyr-Pro, attenuates amyloid ß peptide25-35-induced memory impairment in mice.

In this study, experiments on amyloid ß peptide25-35-induced mice were performed to provide in vivo evidence on the potential of the blood-brain barrier transportable soy dipeptide, Tyr-Pro, in combating memory impairment. We demonstrated for the first time that oral administration of Tyr-Pro (100 mg/kg, twice a day) in mice for 16 days significantly improved impaired memory by spontaneous alternation and shortened step-through latency in amyloid ß-induced mice.

Brain-transportable dipeptides across the blood-brain barrier in mice.

Apart from nutrients required for the brain, there has been no report that naturally occurring peptides can cross the blood-brain barrier (BBB). The aim of this study was to identify the BBB-transportable peptides using in situ mouse perfusion experiments. Based on the structural features of Gly-N-methylated Gly (Gly-Sar), a reported BBB-transportable compound, 18 dipeptides were synthesized, and were perfused in the mouse brain for two minutes. Among the synthesized dipeptides, Gly-Sar, Gly-Pro, and Tyr-Pro were transported across the BBB with Ki values of 7.60 ± 1.29, 3.49 ± 0.66, and 3.53 ± 0.74 µL/g·min, respectively, and accumulated in the mouse brain parenchyma. Additionally, using MALDI-MS/MS imaging analysis of Tyr-Pro-perfused brain, we provide evidence for Tyr-Pro accumulation in the hippocampus, hypothalamus, striatum, cerebral cortex, and cerebellum of mouse brain.