STING activation improves T-cell-engaging immunotherapy of acute myeloid leukemia

T-cell recruiting bispecific antibodies (BsAbs) are in clinical development for relapsed/refractory acute myeloid leukemia (AML). Despite promising response rates, early clinical trials have failed to demonstrate durable responses. Here we investigated whether activation of the innate immune system through stimulator of interferon genes (STING) can enhance target-cell killing by a BsAb targeting CD33 (CD33 BiTE® molecule). Indeed, we show that cytotoxicity against AML mediated by the CD33 BiTE molecule AMG 330 can be greatly enhanced when combined with the STING agonist 2',3'-cyclic GMP–AMP (cGAMP). We used invitro cytotoxicity assays, immunoblotting, transcriptomic analyses, and extensive CRISPR–Cas9 knockout experiments to investigate the enhancing effect of cGAMP on the cytotoxicity of AMG330 against AML. Mechanistically, activated T cells prime target AML cells to STING activation through their effector cytokines interferon-gamma (IFN?) and tumor necrosis factor (TNF), leading to increased production of typeI interferons and induction of interferon-stimulated genes. This feeds back to the T cells, leading to a further increase in effector cytokines and an overall cytotoxic T-cell phenotype, contributing to the beneficial effect of cGAMP in enhancing AMG330-mediated lysis. As such, we establish a key role for IFN? in AMG 330-mediated cytotoxicity against AML cells, as well as in rendering AML cells responsive to STING agonism. Here, we propose to improve the efficacy of CD33-targeting BsAbs by combining them with a STING agonist. Overall design: HL-60 and human T cells from three different healthy donors were co-cultured for 8 h in the presence of AMG 330 ± cGAMP, and separated by FACS before subjecting them to RNA-sequencing. Dataset shows gene expression data for T cells across all conditions (cBiTE, cBiTE+cGAMP, AMG330, AMG330+cGAMP) and donors for every mapped gene following demultiplexing, mapping, filtering, normalization across conditions and variance-stabilizing-transformation by zUMIs and in R