Targeting ASH1L histone methyltransferase in leukemia

Acute leukemia represents a group of diseases associated with distinct genetic alterations that lead to differentiation block and increased proliferation of hematopoietic progenitor cells. Patients with Acute Myeloid Leukemia (AML) have very poor prognosis with currently available treatments, reflected by only ~27% 5-year survival rate. Upregulation of HOX genes is associated with numerous cancers, including acute leukemias. In AML the elevated level of HOX genes, in particular HOXA9, is associated with refractory or relapsed disease and very poor clinical outcome, supporting the urgent need for new therapies. Therefore, small molecules capable of reducing the expression level of HOX genes are highly desired as they should represent novel promising treatment strategies for acute leukemia patients. ASH1L (Absent, small or homeotic 1-like) protein is a histone methyltransferase, which belongs to the Trithorax group of proteins regulating HOX genes expression. Knockdown studies demonstrated the critical role of ASH1L in the development of acute leukemia with MLL1 (KMT2A) translocations, which are associated with HOXA9 and MEIS1 overexpression. Furthermore, our own studies validated that the catalytic SET domain of ASH1L plays a crucial role in leukemogenesis, supporting ASH1L as a valid therapeutic target in acute leukemias with upregulated HOX genes. We developed first-in-class small molecule inhibitors of ASH1L, which bind to the catalytic SET domain and inhibit its histone methyltransferase activity. Medicinal chemistry optimization resulted in compounds with nanomolar binding affinities and high selectivity to ASH1L. Our ASH1L inhibitors strongly block proliferation, induce differentiation and downregulate HOXA genes in the ASH1L-dependent leukemia cells through reduction of H3K36me2 level, supporting the on-target mechanism of action. We also demonstrated that our ASH1L inhibitors reduce leukemia burden and block leukemia progression in vivo in mouse models of the MLL1- rearraged leukemia. In this project we propose to develop the next generation of ASH1L inhibitors with optimized potency and drug-like properties. We will apply highly interdisciplinary approach, involving medicinal chemistry, structure-based design, biochemistry, pharmacokinetic (PK) and biological studies, to develop highly optimized ASH1L inhibitors with strong in vivo efficacy in aggressive models of high HOXA leukemia. In Aim 1, we will employ medicinal chemistry to improve potency and drug-like properties, including metabolic stability, PK and solubility, of the lead compounds that we already identified. In Aim 2, we will characterize new ASH1L inhibitors in a panel of high HOXA leukemia cells and primary patient samples to assess their potency and mechanism of action. Aim 3 will be devoted to assess in vivo efficacy of our new ASH1L inhibitors in advanced leukemia models. We expect this work will result in the next generation of ASH1L inhibitors with strong activity and optimized drug- like properties that will provide novel therapeutic approach for acute leukemia. Project Number: 1R01CA307372-01 | Fiscal Year: 2026 | NIH Institute/Center: National Cancer Institute (NCI) | Principal Investigator: Jolanta Grembecka | Institution: UNIVERSITY OF MICHIGAN AT ANN ARBOR, ANN ARBOR, MI | Award Amount: $646,881 | Activity Code: R01 | Study Section: Drug Discovery and Molecular Pharmacology C Study Section[DMPC] View on NIH RePORTER: https://reporter.nih.gov/project-details/11274946