Design of an Oral STING Agonist through Intramolecular Hydrogen Bond Ring Mimicking to Achieve Complete Tumor Regression.

Stimulator of interferon genes (STING) is a promising target for cancer immunotherapy. However, current development of STING agonist was limited by poor therapeutic efficacy. Herein, we designed potent oral STING agonists through intramolecular hydrogen bond ring mimicking strategy. Structure optimization identified lead compound ZSA-215 with potent cellular STING-stimulating activity. ZSA-215 enhanced STING signaling through promoting the phosphorylation of STING and interferon regulatory factor 3 (IRF3) and secretion of IFN-β. Notably, monotherapy of oral ZSA-215 achieved complete tumor regression and long-term survival of mice in MC38 colon cancer model, which is superior to MSA-2. Furthermore, ZSA-215 exhibited excellent metabolic and chemical stability in vitro, high oral drug exposure (AUC = 23835.0 h·ng/mL) and bioavailability (F = 58%). These results suggest that ZSA-215 is a potent oral STING agonist warrant further development for cancer immunotherapy.