Potent P-glycoprotein (P-gp) inhibitor (IC50 = 5.1 nM). Reverses drug resistance in multiple MDR cell lines. Acts as a substrate for breast cancer resistance protein (BCRP) at low concentrations and acts as an inhibitor of BCRP when used at >100 nM concentration. Potentiates the cytotoxic effects of doxorubicin (Cat. No. 2252) and mitoxantrone (Cat. No. 4250) in vitro. Purity 98%. MW (observed): 719.66