Catalytic Inhibition of KAT6/KAT7 Enhances the Efficacy and Overcomes Primary and Acquired Resistance to Menin Inhibitors in MLL Leukemia.

UNLABELLED: Targeting MYST acetyltransferases is an exciting therapeutic opportunity in acute myeloid leukemia (AML). In this study, we define the individual and combined contribution of KAT6A, KAT6B, and KAT7 in a range of AML models, showing that although KAT6A/B inhibition is efficacious in some preclinical models, simultaneous targeting of KAT7, with the novel inhibitor PF-9363, markedly increases efficacy. KAT7 interacts with menin and the mixed lineage leukemia (MLL) complex and is colocalized at chromatin to coregulate oncogenic transcriptional programs. Focusing on MLL fusion oncoprotein (MLL-FP) AML, we show that inhibition of KAT6/KAT7 provides an orthogonal route to targeting menin to disable the transcriptional activity of the MLL-FP. Combined inhibition rapidly evicts the MLL-FP from chromatin, potently represses oncogenic transcription, and overcomes primary resistance to menin inhibitors. Notably, KAT7 remains an important targetable dependency in acquired genetic/nongenetic resistance to menin inhibition, providing the molecular rationale for rapid clinical translation of combination therapy, particularly in MLL-FP AML.

SIGNIFICANCE: This study provides the molecular rationale for combined targeting of KAT6/7 and menin in MLL leukemia. It reveals that combination therapy results in a rapid and profound repression of the MLL transcriptional program leading to marked differentiation and loss of leukemia-initiating capacity, setting the platform for clinical translation.