The structure of these hybrid inhibitors containsboth P-gp and hCA XII binding moieties to synergistically overcomethe P-gp-mediated MDR in cancer cells that overexpress both proteins;thus, they presented the N,N-bis(alkanol)aminearyl diester group carrying a coumarin group on the nitrogen atom.All compounds showed inhibitory activities on P-gp and hCA XII proteinstaken individually; in fact, they were able to enhance the cytotoxicityof the anticancer drug doxorubicin in resistant K562/DOX cells thatoverexpress only P-gp and inhibited hCA XII at nanomolar concentrations. This evidence concerns the gene PGP and cancer.