Core binding factors (CBFs) are heterodimeric transcription factors consisting of a DNA-binding CBFα component (a RUNX protein) and an enhancer of binding, CBFβ. CBF dimers have central roles in hematopoiesis and, when dysfunctional, in leukemias. CBFβ inhibitor is a small molecule that binds to CBFβ and inhibits its association with Runx1 (IC50 = 3.2 μM). It blocks CBFβ-Runx1 interactions in ME-1 cells, acute myeloid leukemia cells harboring dysfunctional CBF, reducing proliferation without toxicity.