While drugs targeting activating mutations like FLT3 and alterations key to leukemogenesis (e.g., menin and aberrant IDH enzymes) offer important progress in precision approaches to AML, the mutations more often found in MDS or chronic myelomonocytic leukemia (CMML) are ripe for targeting. The gene discussed is IDH1; the disease is chronic myelomonocytic leukemia.