The fact that KMT2A-rearranged ALL cell line models carrying p53 mutations that most likely result in a loss of tumor suppression function (including apoptosis induction) completely fail to respond to Idasanutlin or to other MDM2 inhibitors, such as Milademetan and AMG232, underlines the specificity of these agents. Here, TP53 is linked to acute lymphoblastic leukemia.