ABCB1 and cancer: Thisultimately leads to maintaining, extending, and/or shifting of theresistance profile of multidrug-resistant cancer.6 Hence, multitarget ABC transporter inhibition might bea novel and promising approach to treat multidrug-resistant cancer.However, the simultaneous targeting of ABCB1, ABCC1, and ABCG2 hasonly very recently been emphasized.6,14−17 The term broad-spectrum inhibition itself goes back to mid-2000s.18 Since then, it was only infrequently acknowledged19−22 and has only been addressed properly within the last couple of years.6,14−17,23,24