The host STING pathway plays a critical role in innate immune sensing of cancer, that drives type-I interferons (IFNs) production and promotes aggressive antitumor responses. Compound DMXAA is an agonist of mouse STING (mSTING) and demonstrated potent antitumor activities in several tumor models, including melanoma. However, DMXAA cannot activate human STING (hSTING), which provides a possible rationale for its failure in recent clinical trial. In this project, we aim to identify novel chemical compounds as potent STING agonists. By combining structure-based drug design and in vitro assays, we have discovered two initial hits as STING agonists that belong to two different chemical scaffolds. Direct binding of our compounds with hSTING was confirmed by Surface plasmon resonance (SPR) analysis. Chemical optimization of our initial hits has led to compound #150 and #171. We demonstrated that #150 and #171 at 10 uM have substantially activated STING pathway in HEK293 cells that were transiently transfected with plasmid expressing hSTING. Compound #171 at 20 uM potently activated STING signaling in human THP-1 cells that harbor hSTINGHAQ as well as PBMC cells from a panel of human donors. Importantly, with DMXAA as the control, we demonstrated that #171 at 20 mg/kg via i.p. has significant antitumor effect against TRAMP-c1 tumor in C57/BL6 mice.

Citation Format: Jian Hui Wu. Identification and optimization of chemical compounds as potent agonists of human STING with anticancer activity in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3849.