Abstract P14: Efficacy of FHD-286 monotherapy and combinations against Menin inhibitor sensitive and resistant AML cells

Abstract

Abstract BRG1 (SMARCA4) and BRM (SMARCA2) are the core ATPase within the BAF chromatin remodeler complexes. FHD-286 (Foghorn Therapeutics) is a potent, selective, oral inhibitor of BRG1/BRM in clinical development in AML. Present studies show that FHD-286 induces marked in vitro differentiation and loss of viability in AML cell lines and patient-derived (PD) AML cells with MLLr or mutant (mt) NPM1. FHD-286 treatment concordantly reduced genome-wide ATAC-Seq and RNA-Seq peaks, with negative enrichment at the gene-sets of MYC and E2F targets, mTORC1 signaling, translation initiation/elongation and DNA replication. FHD-286 reduced the occupancy of BRG1 and H3K27Ac on the chromatin. Mass spectrometry revealed FHD-286 reduced protein levels of c-Myc (and its targets), PLK1, BCL2, PU.1 and CDK4, but increased HEXIM1, CDKN1A/1B, CEBPα and CD11b levels. CyTOF analysis in the phenotypically characterized, PD, AML stem/progenitor cells with MLL1r or mtNPM1 showed decline in the protein levels of c-Myc, PU.1, BRG1, MEF2C, PBX3, BCL2 and MCL1, but increase in cleaved PARP and caspase-3 levels. In a PD xenograft (PDX) model of MLL1r AML, monotherapy with FHD-286 (oral gavage) for 4 to 6-weeks reduced AML burden and improved survival. FHD-286 treatment also significantly inhibited the AML-initiating potential, by reducing AML burden and improving survival of the re-engrafted mice with the FHD-286-treated PDX cells. Co-treatment with FHD-286 and BET inhibitor (OTX015), Menin inhibitor (MI, SNDX-50469), decitabine or venetoclax, exerted synergistic lethality in AML cell lines and PD AML cells with MLL1r or mtNPM1. Importantly, co-treatment with FHD-286 and OTX015, SNDX-5613 (oral gavage), venetoclax or decitabine vs each drug alone significantly reduced AML burden and improved survival in the PDX models of AML cells with MLLr or with mtNPM1, without significant toxicity. Notably, FHD-286 also induced significant lethality in MI-resistant AML cell lines and PD AML cells. Through repeated shocks with LD90 dosing of MI, followed by drug washout and recovery, we have generated MLL1r (MV4-11-MITR) and mtNPM1 (OCI-AML3-MITR) AML cell lines that are tolerant/resistant (TR) to MI (without exhibiting Menin mutations) with LD50 values greater than 1 µM. A domain-specific CRISPR screen in MV4-11-MITR cells identified several druggable co-dependencies (e.g., EP300 and MOZ) and co-enrichments (SMARCA4, CREBBP and BRD4) with MI. Accordingly, co-treatment with FHD-286 and OTX015, SNDX-50469 or CBP/p300 inhibitor GNE781 exerted synergistic lethality in MV4-11-MITR and OCI-AML3-MITR cells as well as in PD MITR AML cells with MLL1r or mtNPM1. FHD-286 and OTX015 or SNDX-5613 treatment also reduced AML burden in mice bearing OCI-AML3-MITR xenografts. These findings demonstrate pre-clinical efficacy of FHD-286-based rational combinations and underscore their promise against MI-sensitive or resistant AML with MLL1r or mtNPM1. Citation Format: Warren C Fiskus, Jessica Piel, Murphy Hentemann, Mike Collins, Christopher P Mill, Branko Cuglievan, Courtney D DiNardo, Kapil N Bhalla. Efficacy of FHD-286 monotherapy and combinations against Menin inhibitor sensitive and resistant AML cells [abstract]. In: Proceedings of the Blood Cancer Discovery Symposium; 2024 Mar 4-6; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(2_Suppl):Abstract nr P14.