ABCB1 and cancer: Summing up, the performed SAR analysis allowed us to recognize chemical moieties that could be beneficial for the action on the cancer ABCB1-efflux pump, i.e., the fluorene, phenoxyphenyl, or anthracene as aromatic moieties of 5-arylideneimidazolone on the one hand, and either the morpholine-piperidine at position 2 or the propyl-linked morpholine at position 3 of the imidazolone core, on the other.