Western blot analyses of cell lysates from one sample each of AML blasts with MLL1-r (sample #5) or with mtNPM1 (sample #11) demonstrated that treatment with ziftomenib reduced protein expressions of Menin, MEIS1, FLT3, CDK6, BCL2, with HOXA9 and MEF2C levels declining only in MLL1-r AML (Fig. 1F and Supplementary Fig. S6C). Here, MEF2C is linked to acute myeloid leukemia.