Discovery of 3-(Fluoro-imidazolyl)pyridazine Derivatives as Potent STING Agonists with Antitumor Activity

Stimulator of interferon genes (STING) represents a promising therapeutic target for cancer and infectious diseases due to its ability to activate innate immune responses. Herein, we describe the discovery of 3-(fluoro-imidazolyl) pyridazine derivatives as potent STING agonists. Our comprehensive investigation, including structural and functional analysis as well as molecular dynamics simulation, suggests that appropriate spatial dimensions may play a crucial role in determining agonist efficacy. Notably, our representative STING agonist A4 demonstrates remarkable binding affinities to various hSTING variants and mSTING, effectively activating STING in both human THP1 and mouse RAW 264.7 cells with EC₅₀ values of 0.06 and 14.15 μM, respectively. Furthermore, Compound A4 exhibits an excellent pharmacokinetic profile in C57BL/6 mice, and its systemic administration led to significant tumor regression in the B16.F10 tumor-bearing mice, surpassing the efficacy of SR-717. These findings position A4 as a highly promising STING agonist warranting further advanced preclinical development for tumor immunotherapy.