Abstract 1140: Pre-clinical efficacy of targeting BAF complexes through inhibition of the dual ATPases BRG1 and BRM by FHD-286 in cellular models of AML
Authors: Fiskus Warren C. , Piel Jessica , Hentemann Murphy , Mill Christopher P. , Birdwell Christine E. , Das Kaberi , Davis John A. , Kadia Tapan M. , Daver Naval , Loghavi Sanam , DiNardo Courtney D. , Bhalla Kapil N. 
Published: April 2023

Abstract
ATP-dependent chromatin remodeling BAF (BRG1/BRM-associated factor) complexes bind and enable transcription factors (TFs) and co-factors to gain access to enhancer/promoter DNA and modulate transcription. In BAF complexes, The BRG1 (SMARCA4) or BRM (SMARCA2) is the core ATPase. AML stem/progenitor cells (LSCs) express and are dependent on BRG1/BRM activity to maintain their dysregulated epigenome/transcriptome, especially driven by mutations in epigenetic regulators and TFs. CRISPR-dependency DepMap also shows dependency on SMARCA4 in numerous AML cell lines. FHD-286 is a selective, oral inhibitor of BRG1/BRM in early clinical development as a therapy for AML. Our present studies demonstrate that exposure to FHD-286 (10 to 100 nM) for 7 days induces differentiation followed by loss of viability of AML cell lines and PD AML cells with MLL rearrangement (r), mutant (mt) NPM1 and chromosome 3q26 lesions (with EVI1 overexpression). Treatment with FHD-286 caused whole-genome, concordant, up- or down-regulations in ATAC-Seq peaks and RNA-Seq-determined mRNA expressions of specific loci, associated with significant reduction in the gene-sets of targets of MYC, mTORC1, E2F, Interferon-gamma, IL6-JAK-STAT3, as well as of inflammatory response and oxidative phosphorylation genes. QPCR analyses determined significant reduction in mRNA expression of MYC, SPI1 and BCL2 genes. Mass spectrometry on AML cell lysates treated with FHD-286 showed log2 fold-reductions in c-Myc, SPI1, MEF2C, KMT2C and CDK4 (in MOLM13) and in EVI1, c-Myb, CDK6 and c-Myc (in AML191) cells. Co-treatment with FHD-286 and venetoclax, decitabine or BET inhibitor (OTX015) exerted synergistic in vitro lethality against AML cell lines and PD AML cells, especially those expressing MLL-r, mtNPM1 or EVI1 (Delta synergy scores &gt; 5 by the ZIP method). Based on the known efficacy of the Menin inhibitor SNDX-50469, we also found that co-treatment with FHD-286 and SNDX-50469 was synergistically lethal against AML cell lines and PD AML cells with MLL-r or mtNPM1. Finally, in a luciferase-transduced, patient-derived xenograft (PDX) model of AML cells with MLL-AF9, FLT3, KMT2C/2D and NOTCH2 mutations, we determined that treatment with FHD-286 administered orally alone for 4 to 6 weeks was significantly effective in reducing AML burden and improving overall survival of the mice. Additionally, co-treatment with FHD-286 and venetoclax, decitabine or OTX015, as compared to each drug alone or vehicle control, significantly reduced AML burden and improved the overall survival of the NSG mice, without inducing significant toxicity. Taken together, these findings highlight the promise of FHD-286 treatment alone and in rational combinations in exerting significant anti-AML efficacy against cellular models of AML, especially those with MLL-r, mtNPM1 or chromosome 3q26 lesions and EVI1 overexpression.
Citation Format: Warren C. Fiskus, Jessica Piel, Murphy Hentemann, Christopher P. Mill, Christine E. Birdwell, Kaberi Das, John A. Davis, Tapan M. Kadia, Naval Daver, Sanam Loghavi, Courtney D. DiNardo, Kapil N. Bhalla. Pre-clinical efficacy of targeting BAF complexes through inhibition of the dual ATPases BRG1 and BRM by FHD-286 in cellular models of AML [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1140.