Aim: To determine if a test compound is substrate of an efflux transporter, either P-gp (P-glycoprotein) or BCRP (breast cancer resistance protein multidrug transporter), using the Caco-2 cell model.

Background information: Caco-2 cells are a human colon adenocarcinoma cell line which express efflux transporters, such as P-gp and BCRP. Efflux transporters are involved in drug absorption and disposition. As transporter substrates, drugs can be victims of drug-drug interactions in the clinical practice.

Transport assays are conducted both in the absorption (apical-to-basolateral) and efflux (basolateral-to-apical) directions. Test compound is added to either the apical or basolateral sides of the monolayer in the absence and presence of transporter reference inhibitor. Concentrations are quantified by UPLC-MS/MS using a calibration curve.