%0 Journal Article %A Ryota Kikuchi %A Sonia M. de Morais %A John Cory Kalvass %T In Vitro P-gp Efflux Ratio Can Predict The In Vivo Brain Penetration Regardless of BDDCS Class %D 2013 %R 10.1124/dmd.113.053868 %J Drug Metabolism and Disposition %P dmd.113.053868 %X P-glycoprotein (P-gp) is expressed at the blood-brain barrier (BBB) and restricts the penetration of its substrates into the central nervous system (CNS). In vitro substrate assessment for P-gp is frequently used to predict the in vivo relevance of P-gp-mediated efflux at the BBB. We have conducted a comprehensive review of literature focusing on the in vitro-in vivo correlation of P-gp efflux ratio (ER), and demonstrated that in vitro substrates of P-gp are also in vivo substrates at the BBB. It was of note that the in vitro ER in MDCK-MDR1 cell line from National Institute of Health was found to be a better predictor of in vivo ER compared with that from Netherlands Cancer Institute with r2 values of 0.813 and 0.531, respectively. Recently, Broccatelli and coworkers have proposed that 98% of Biopharmaceutics Drug Disposition Classification System (BDDCS) class 1 drugs can penetrate the brain even when those compounds are shown as P-gp substrates in vitro (Broccatelli et al., 2012). However, our data analysis suggested that in vitro ER can predict the in vivo brain penetration regardless of the class in BDDCS. Considering that very few marketed CNS drugs are in vivo substrates for P-gp, the in vitro substrate assessment of P-gp should be used in the early stages of drug discovery to select compounds which most likely penetrate the CNS to exert their pharmacological action. %U https://dmd.aspetjournals.org/content/dmd/early/2013/09/05/dmd.113.053868.full.pdf