STING agonist C11 is an agonist of the stimulator of interferon genes (STING) pathway.1 It induces secretion of type I IFN from THF and MM6 cells when used at a concentration of 50 μM. STING agonist C11 induces phosphorylation of IFN regulatory factor 3 (IRF3) and increases expression of IFIT1 and viperin, but not IL-1β, IL-6, or IL-8 in THF cells in a STING-dependent manner. It reduces viral titers of chikungunya, Venezuelan equine encephalitis, o'nyong-nyong, Mayaro, and Ross River viruses grown in THF cells (EC90s = 16.44, 16.7, 18.84, 25.19, and 22.57 μM, respectively), an effect that is dependent on the presence of STING and the IFN-α/β receptor (IFNAR).