Abstract 4475: Discovery of an oral tricyclic STING agonist with superior pharmacokinetic properties and potent in vivo efficacy

Abstract Stimulator of interferon genes (STING) plays a pivotal role in regulating immune microenvironment for cancer immunotherapy. However, the use of most STING agonists has been hindered by the necessity for intra-tumoral or intravenous administration, underscoring the challenge in developing an orally bioavailable STING agonist with favorable pharmacokinetic (PK) properties. In this study, we discovered oral STING agonists featuring a novel tricyclic benzo4, 5thieno2, 3-cpyrrole-1, 3-dione scaffold, thus achieving both superior PK properties and potent in vivo efficacy. Our lead compound, ZSA-51, exhibited nanomolar cellular STING activation activity (EC50 = 100 nM) in THP1 cells, surpassing the reported oral STING agonist MSA-2 by 32-fold (EC50 = 3200 nM). Furthermore, ZSA-51 demonstrated superior PK properties with an oral bioavailability of 49%, and robust in vivo antitumor activity both in colon and pancreatic cancers model upon oral administration. Notably, ZSA-51 displayed preferential distribution to the lymph nodes and spleen, enhancing its systemic immune-stimulating effects. The specificity of ZSA-51 was further confirmed by a comparison with a negative control compound (ZSA-52NC2) that was unable to stimulate in vitro and in vivo STING activity. Molecular docking and MD simulation confirmed that the active form of ZSA-51 stably bound to STING dimer with validated hydrogen bond network. Taken together, our findings suggest ZSA-51 as a promising oral STING agonist characterized by superior PK properties and potent in vivo efficacy, holding potential for future development for cancer immunotherapy. Citation Format: Hong-Yi Zhao, Zhongwei Liu, Shuai Mao, Miao He, Meilin Wang, Bo Wen, Wei Gao, Duxin Sun. Discovery of an oral tricyclic STING agonist with superior pharmacokinetic properties and potent in vivo efficacy abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4475.