Overcoming Menin inhibitor resistance in AML cells with combinations including BET proteins and dual BRG1/BRM inhibitor

Menin inhibitors (MI) disrupt the binding of Menin to MLL1 leading to repression of MLL1 or MLL1-fusion protein (FP) target genes, including reduced levels of HOXA9 and MEIS1 in AML with mutant (mt) NPM1 or MLL1-rearrangement (r). While MIs are relatively well-tolerated and induce clinical remissions, these are often short-lived due to development of resistance followed by AML relapse. Through repeated shocks with the MI SNDX-50469, a precursor tool compound to revumenib, followed by recovery, we developed MI-resistant (MITR) AML MV4-11 and OCI-AML3 cells. Present studies show that, compared to MI-sensitive parental cells, MITR cells exhibit an altered epigenome, transcriptome and proteome, without Menin mutations. Through a CRISPR screen, novel druggable MI co-enrichments were identified and targeted, including BRD4, SMARCA4, and CREBBP. Co-treatment with the MI and the SMARCA4/SMARCA2 (BRG1/BRM) inhibitor FHD-286 or the BET proteins inhibitor OTX015 (birabresib), synergistically induced in vitro lethality in MITR and MI-resistant AML cells expressing the mutant Menin (M327I), as well as in patient-derived (PD) AML cells with MLL1-r or mtNPM1 that exhibited ex vivo resistance to MI. Compared to each drug alone, co-treatment with SNDX-5613 (revumenib) and FHD-286 or OTX015 and FHD-286 significantly reduced the in vivo AML burden and improved survival of the immune depleted mice, without inducing significant toxicity, in the xenograft models of MITR and MI-resistant PD MLL1-r AML cells. These findings highlight novel, targeted, drug combinations that overcome MI resistance in AML cells with MLL1-r or mtNPM1.