Development and Validation of a 2’3’-cGAMP ELISA Daniel Tew, Tatyana Maxey, and Yogan Khatri Cayman Chemical Company, Ann Arbor, Michigan. Cyclic GMP-AMP synthase (cGAS) is a cytosolic DNA sensing enzyme that detects the presence of nucleic acids in the cytosol of mammalian cells as an indicator of bacterial or viral infection.1 cGAS catalyzes the synthesis of a second messenger, 2’3’-cyclic GMP-AMP (2’3’-cGAMP), from cytosolic ATP and GTP in response to dsDNA binding. 2’3’-cGAMP then binds tightly to the adaptor protein stimulator of interferon genes (STING), resulting in the recruitment of TANK-binding kinase 1 (TBK1) and subsequent interferon regulatory factor 3 (IRF3) phosphorylation.2 IRF3 induces the transcription and translation type I interferon, a potent antiviral cytokine.3 Activation of cGAS and the production of 2’3’-cGAMP are important in host defense, but also may play role in autoimmune or inflammatory diseases. Modulation of cGAS activity, with subsequent inhibition of induction of 2’3’-cGAMP formation is an active target of pharmacological intervention.4 This report will focus on the development and validation of a novel 2’3’-cGAMP enzyme linked immunoassay (ELISA). The data provided will demonstrate its value as an enzymatic readout from cell-lysates and purified human recombinant cGAS.