STING-IN-8 (Compound 15b) is a potent inhibitor of the stimulator of interferon genes (STING), with an IC50 value of 0.121 μM in humans and 0.033 μM in mice. This compound effectively inhibits STING signaling induced by MSA-2 or 2',3'-cGAMP, as well as the levels of immune and inflammatory cytokines in human and mouse cells. STING-IN-8 shows significant potential for research in STING-related inflammatory and autoimmune diseases.