– 2’2′-cGAMP is a synthetic dinucleotide (CDN) that contains non-canonical 2’5′-phosphodiester bonds. It binds to the adapter protein stimulator of interferon genes , which is a component of the innate immune response that activates the type I interferon pathway when bound to cyclic dinucleotides. 2’2-cGAMP shows weaker binding to STING than 2’3′-cGAMP but binds more strongly than 3’3′-cGAMP , cyclic di-GMP , or 3’2′-cGAMP, which bind in the micromolar range (Kds = 1.04, 1.21, or 1.61 μM, respectively). Despite weaker binding, 2’2′-cGAMP induces IFN-β production in the same concentration range as 2’3′-cGAMP (EC50s = 15.8 and 19.4 nM, respectively, in L929 cells).