Emerging evidence indicates an important role for breast cancer resistance protein (BCRP) in limiting brain penetration of substrate drugs. While in vitro Transwell® assays can provide an indication of BCRP substrate potential, the predictability of these to in vivo brain penetration is still under debate. The present study examines the correlation of BCRP protein concentration and transcellular transport activity across MDCKII monolayers. We expressed human BCRP or murine Bcrp1 in MDCKII wild-type cells using BacMam2 virus transduction. The selective P-glycoprotein (P-gp) inhibitor LY335979 (1 μM) was included in transport medium to measure BCRP-mediated transcellular transport for P-gp and BCRP co-substrates. BCRP protein levels in membrane extracts from MDCKII-BCRP or MDCKII-Bcrp1 cells were quantified by liquid chromatography-tandem mass spectrometry. The results are summarized as follows: 1) membrane protein concentrations correlates with corrected efflux ratios of substrates for human BCRP and murine Bcrp1 within the efflux ratios investigated; 2) we demonstrate a good concordance in rank order between BCRP and Bcrp1 mediated efflux ratios for 12 drugs; 3) we propose an approach to contextualize in vitro BCRP transport data of discovery compounds by comparing to the in vitro and in vivo transport data of reference drug dantrolene and taking into account inter-batch variation in BCRP protein expression. This approach correctly predicted compromised brain penetration for 22 proprietary discovery compounds in rodents, which were BCRP but not, or weak P-gp substrates. These results suggest that BCRP-expressing MDCKII cells are useful for predicting the in vivo role of BCRP in brain penetration.
- blood-brain barrier
- efflux transporters (P-gp, BCRP, MRP, MATE, BSEP, etc)
- in vitro-in vivo prediction (IVIVE)
- The American Society for Pharmacology and Experimental Therapeutics