After chemotherapy, tumor cells with multidrug resistance (MDR) often emerge. MDR is attributable to the expression of membrane transport proteins that inhibit the cellular influx and increase the efflux of many chemotherapeutic drugs. One such protein is P-glycoprotein (P-gp), which functions as an ATP-dependent active transporter. Recently, an anti-P-gp monoclonal antibody (MAb) that inhibits...