ABCB1 and cancer: To confirm that erdafitinib reverses ABCB1-mediated multidrug resistance by restoring the cytotoxicity of cytotoxic drugs in ABCB1-overexpressing cancer cells and not by initiating a growth retardation effect, the effect of erdafitinib on drug-induced apoptosis in ABCB1-overexpressing cancer cells was examined.