In this issue of EMBO Molecular Medicine, Liu et al show that inosine monophosphate dehydrogenase (IMPDH) inhibitors, the well‐known immunosuppressants have a potent therapeutic effect on the aggressive blood cancer, acute myeloid leukemia with MLL rearrangements. The gene discussed is KMT2A; the disease is hematopoietic and lymphoid system neoplasm.