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Validation of membrane vesicle-based breast cancer resistance protein and multidrug resistance protein 2 assays to assess drug transport and the potential for drug–drug interaction to support regulatory submissions

Breast cancer resistance protein (BCRP) and multidrug resistance protein 2 (MRP2) can play a role in the absorption, distribution, metabolism, and excretion of drugs, impacting on the potential for drug–drug interactions. This study has characterized insect cell– and mammalian cell–derived ABC-transporter–expressing membrane vesicle test systems and validated methodologies for evaluation of candidate drugs as substrates or inhibitors of BCRP or MRP2. Concentration-dependent uptake of BCRP ([3H]oestrone 3-sulfate, [3H]methotrexate, [3H]rosuvastatin) and MRP2 ([3H]oestradiol 17β-glucuronide, [3H]pravastatin, carboxydichlorofluorescein) substrates, and inhibitory potencies (IC50) of BCRP (sulfasalazine, novobiocin, fumitremorgin C) and MRP2 (benzbromarone, MK-571, terfenadine) inhibitors were determined. The apparent Km for probes [3H]oestrone 3-sulfate and [3H]oestradiol 17β-glucuronide was determined in insect cell vesicles to be 7.4 ± 1.7 and 105 ± 8.3 µM, respectively. All other substrates exhibited significant uptake ratios. Positive control inhibitors sulfasalazine and benzbromarone gave IC50 values of 0.74 ± 0.18 and 36 ± 6.1 µM, respectively. All other inhibitors exhibited concentration-dependent inhibition. There was no significant difference in parameters generated between test systems. On the basis of the validation results, acceptance criteria to identify substrates/inhibitors of BCRP and MRP2 were determined for insect cell vesicles. The approach builds on earlier validations to support drug registration and extends from those cell-based systems to encompass assay formats using membrane vesicles.