Abstract B18: Development of human STING agonists for prostate cancer immunotherapy

Abstract

Abstract Recent studies have identified the host STING pathway as a critical mechanism of innate immune sensing of cancer, that drives type-I interferons (IFNs) production and promotes aggressive antitumor responses. Thus, STING agonists could be candidates for testing as stimulants for anticancer immune activity. Although DMXAA binds and activates mouse STING, it cannot activate human STING (hSTING). This species specificity is thought to be the reason that DMXAA showed dramatic effect against solid tumor in rodent models, but failed in human clinical trials. In this project, we aim to identify novel chemical compounds as agonists of hSTING. By combining in silico screening and in vitro assays, we have discovered two novel chemical compounds that activate hSTING. Direct binding of our compounds with hSTING was confirmed by Surface plasmon resonance (SPR) analysis. We demonstrated that our hSTING agonist activated interferon signaling pathway in monocytic human THP-1 cells, which express endogenous hSTING. Further, our compound itself is not cytotoxic to 22Rv1 prostate cancer cells, but the spent supernatants of the THP-1 cells exposed to our compound are cytotoxic to 22Rv1 cells. Chemical optimization of initial active compounds is in progress. We aim to generate compound candidates as potent hSTING agonists for in vivo evaluation in rodent models. Note: This abstract was not presented at the conference. Citation Format: Jian Hui Wu. Development of human STING agonists for prostate cancer immunotherapy. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr B18.