2',3'-Cyclic GMP-AMP Dinucleotides for STING-Mediated Immune Modulation: Principles, Immunotherapeutic Potential, and Synthesis.

The cGAS-STING pathway discovered ten years ago is an important component of the innate immune system. Activation of cGAS-STING triggers downstream signalling, such as TBK1-IRF3, NF-κB and autophagy, which in turn leads to antipathogen responses, durable antitumour immunity or autoimmune diseases. 2',3'-Cyclic GMP-AMP dinucleotides (2',3'-cGAMP), the key second messengers produced by cGAS, play a pivotal role in cGAS-STING signalling by binding and activating STING. Thus, 2',3'-cGAMP has immunotherapeutic potential, which in turn has stimulated research on the design and synthesis of 2',3'-cGAMP analogues for clinical applications over the past ten years. This review presents the discovery, metabolism, and function of 2',3'-cGAMP in the cGAS-STING innate immune signalling axis. The enzymatic and chemical syntheses of 2',3'-cGAMP analogues as STING-targeting therapeutics are also summarized.