Ribociclib, a CDK4/6 inhibitor approved for the treatment of locally advanced/ metastatic breast cancer, revealed ABCB1 and ABCG2-mediated daunorubicin and mitoxantrone efflux inhibition in AML cell lines and in CD4+/Flt3-WT leukemia cells [117]. The gene discussed is ABCG2; the disease is leukemia.