Models for predicting efflux transport over the blood-brain barrier

Sammanfattning: Aim: The general aim of this research is development and evaluation of novel methods for predicting active transport over the human blood-brain-barrier (BBB), while this project specifically aims to i) review the literature and select suitable methods and substrates, ii) develop models for determining in vitro kinetic properties of selected compounds, analyze the in vitro data using the developed models and to use Maximum Transport Activity (MTA) approach (Karlgren et al., 2012), iii) perform Physiology Based Pharmacokinetic (PBPK) modelling and compare to in vivo literature data. Background: Drug permeation to the brain through blood circulation is primarily limited by blood-brain barrier (BBB), due to existence of tight junctions in endothelial cells of blood vessels as well as active efflux and influx transporters in the barrier. Toxicity and CNS related side effects can be caused by peripheral targeted drugs crossing BBB. Hence, prediction of BBB permeability and estimation of drug concentration in the brain tissue are challenging in drug discovery. To resolve this, estimating the human BBB permeability using improved in vitro and in silico predictive models can be a facilitator. Methods: In vitro data provided by the Drug Delivery research group was used to develop in vitro predictive models for BBB penetration of Verapamil, Risperidone, and Prazosin using R-studio 1.2.5. The MTA approach was adjusted for extrapolation of BBB in vitro transporter activity to in vivo condition. For PBPK modelling, we took advantage of PK-Sim® to simulate drug disposition and time profile of Risperidone in human and animal species. Results: It was shown that MDR1 is the major transporter for efflux transport of Prazosin and Risperidone in brain while both BCRP and MDR1 have similar impact on transport of Verapamil. Furthermore, it was presented in PBPK models that the predicted brain concentration of Risperidone increases in rat and nonhuman primate (NHP) when MDR1 And BCRP are knocked out while the brain concentration of Risperidone in dog is not affected by expression level of the efflux transporters. Conclusion: Both MDR1 and BCRP are contributing in efflux transport of Verapamil, Risperidone, and Prazosin across the BBB. Additionally, expression of the efflux transporters shown to have an impact on brain exposure of Risperidone in animal PBPK models.