Dual targeting of AML by BCL-2 inhibition and by CD123-directed NK engager/NK cell immune therapies

About This Grant

SCIENTIFIC ABSTRACT Acute myeloid leukemia (AML) is an aggressive clonal hematologic malignancy characterized by the defects in differentiation of the myeloid lineage, heightened proliferation, and resilience to cell death. Despite recent FDA approvals of several targeted therapies including venetoclax-based regimens, most patients relapse due to the survival and expansion of residual leukemia blasts and leukemia stem cells (LSCs) evading therapy. Eradiation of these cells through novel therapeutic approaches is critical for curing AML. CD123 is a surface marker strongly expressed on AML blasts and LSCs but largely sparing normal cells including hematopoietic stem cells (HSCs). AFM28 is a novel bispecific Innate Cell Engager (ICE ®)) that in pre-clinical studies effectively depleted CD123+ leukemic cells and LSC through NK cell engagement and recently showed encouraging activity in Phase I monotherapy trial in relapsed/refractory AML. NK-cell-mediated cytotoxicity can be sensitized through BCL-2 inhibition with venetoclax (Ven). Our preliminary data demonstrate that co- targeting of CD123+ AML by NK cells and of BCL2 by Ven translates into apoptosis of both, phenotypically defined AML stem/progenitor cells and AML blasts. We hypothesize that co-targeting AML by CD123- directed NK cells and BCL-2 inhibition harnessing apoptotic machinery will elicit AML cell kill through synergistic mitochondrial apoptotic priming. We will test our hypothesis in Specific Aims: In Aim 1, we will investigate combinatorial efficacy and molecular mechanisms of co-targeting CD123+ AML by NK-cell engager and BCL2 inhibition by Ven. We will perform dynamic BH3 profiling to probe modulation of mitochondrial priming, focusing on mitochondrial membrane integrity, induction of pro-apoptotic proteins, reprogramming of mitochondrial metabolism and co-dependency on mitochondrial pathway in AML and NK cells. In Aim 2, we will first determine the safety of the combination utilizing humanized NSGS mice producing human IL15 that provides support for NK cells maintenance, engrafted with CD123+ AML cell line and treated with AMF28-NK_Ven/Aza. Next, we will study the combinatorial efficacy of AMF28-NK_Ven/Aza in vivo in patient-derived xenograft (PDX) models generated from Ven/Aza-sensitive or -resistant AML. Molecular signatures of each therapeutic arm and combinations will be determined by flow cytometry, immunochemistry, immunophenotypic profiling, methylation assays and scRNAseq. Results of this proposed work will lay the foundation and provide rationale for successfully translating the combination of potent BCL-2 inhibitor with a novel engager AFM28-directed NK cell therapy into curative targeted therapy approach for AML patients.