Characterization of Substrates and Inhibitors for the In Vitro Assessment of Bcrp Mediated Drug–Drug Interactions
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In vitro assessment of drug candidates' affinity for multi-drug resistance proteins is of crucial importance for the prediction of in vivo pharmacokinetics and drug–drug interactions. To have well described experimental tools at hand, the objective of the study was to characterize substrates and inhibitors of Breast Cancer Resistance Protein (BCRP) and P-glycoprotein (P-gp).
Madin–Darbin canine kidney cells overexpressing mouse Bcrp (MDCKII-Bcrp) were incubated with various Bcrp substrates, or a mixture of substrate and inhibitor to either the apical (A) or basolateral (B) compartment of insert filter plates. Substrate concentrations in both compartments at time points t = 0 h and t = 2 h were determined by LC–MS/MS, and respective permeation coefficients (P app) and efflux ratios were calculated.
The Bcrp inhibitor Ko143 blocked topotecan and ABZSO transport in a concentration-dependent manner. P-gp inhibitors ivermectin, LY335979, PSC833, and the P-gp/Bcrp inhibitor ritonavir did not influence Bcrp mediated topotecan transport, however, blocked ABZSO transport. Additionally, neither was ABZSO transport influenced by topotecan, nor topotecan transport by ABZSO.
Data suggest different modes of substrate and inhibitor binding to Bcrp. In order to not overlook potential drug–drug interactions when testing drug candidates for inhibitory potential towards Bcrp, distinct Bcrp probe substrates should be used.
KEY WORDSBcrp drug–drug interaction inhibitor pharmacokinetics substrate
ATP binding cassette transporter B1
ATP binding cassette transporter G2
human placenta-specific ATP-binding cassette gene
breast cancer resistance protein
Dulbecco's modified Eagle’s medium
fetal calf serum
Hanks’ balanced salt solution
porcine kidney tubular epithelial cell line
Madin Darby canine kidney cell line II
mitoxantrone resistance gene
apparent permeability coefficient
transepithelial electrical resistance
We thank Mark Twele for technical assistance during LC–MS/MS analytics.
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