STING agonists in combination with epigenetic drugs potentiate ZNFX1-driven inflammatory necroptosis in TP53 -mutated AML

Abstract

TP53-mutated acute myeloid leukemia (AML) has dismal outcomes with current treatments and represents a critical unmet need. TP53-mutated AML is proposed to be susceptible to immunotherapeutic approaches but, to date, there is no established immunotherapy for this sub-group. Expression of stimulator of interferon genes (STING), a key innate immune driver that activates interferon (IFN) signaling, is decreased by epigenetic silencing or mutation in many cancers, including those with TP53 mutations. Here, we report that response to the next-generation synthetic STING agonist C92 is potentiated in AML cell lines and primary cells with TP53-mutated versus wild-type (WT) cells, representing a previously undescribed vulnerability of these leukemia cells to STING small molecule therapies. Moreover, combining treatment with the DNA methyltransferase inhibitor (DNMTi) decitabine (DAC), significantly increases STING activation, with marked transcriptome-wide increase in repetitive elements (REs) and upregulation of a critical set of interferon-related genes. Cell death in TP53 KO versus WT AML is specifically dependent on innate immune zinc finger NFX1-type containing 1 (ZNFX1) and Z-DNA-binding protein 1 (ZBP1) driving increased cleavage and activation of Receptor-Interacting-Serine/Threonine-Protein Kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL), suggesting mechanisms of necroptosis. Finally, C92 and DAC combination significantly reduces leukemia burden in humanized AML mouse models, accompanied by increased immune responses, including cytokines and cytotoxic T lymphocytes in the leukemia microenvironment. These results support development of clinical trial strategies combining STING agonists with DNMTis for patients with TP53-mutated AML. Summary TP53-mutated AML potentiates effects of novel next-generation STING agonist C92, with unique allosteric and non-cyclic dinucleotide (non-CD) mechanism of action, inducing increased STING activation and cytokine release STING agonists and DNMTis, synergistically increase STING activation with marked transcriptome-wide increase in repetitive elements (REs) and upregulation of a critical set of interferon-related genes in TP53-mutated AML STING agonists induce necroptosis via a STING-ZNFX1-ZBP1-necroptosis axis in TP53-mutated AML. This drug combination reduces leukemia burden, activates immune responses in AML models and supports translation for high-risk AML patients. Statement of Translational Relevance This pre-clinical study identifies a novel therapeutic vulnerability in (TP53)-mutated acute myeloid leukemia (AML), a poor prognosis subtype with a critical unmet need. Novel next-generation STING agonist C92, with unique allosteric and non-cyclic dinucleotide (non-CD) mechanism of action, induces increased STING activation and cytokine release, compared with WT TP53 in AML cell lines and primary cells, and has superior STING activity with respect to several STING agonists currently in clinical studies. Combining C92 treatment with the DNA methyltransferase inhibitor (DNMTi) decitabine (DAC) synergistically increases STING activation, with marked transcriptome-wide increase in repetitive elements (REs) and upregulation of a critical set of interferon-related genes, driving ZNFX1-driven inflammatory necroptotic cell death. Utilizing humanized mouse models, C92 in combination with DAC significantly reduces leukemia burden and enhances cytotoxic T-cell responses in the tumor microenvironment, supporting clinical translation for high-risk AML patients.