2'3'-cGAMP (sodium salt): High-Affinity STING Agonist for Innate Immunity Research

Executive Summary: 2'3'-cGAMP (sodium salt) is an endogenous cyclic dinucleotide that directly binds and activates STING with nanomolar affinity, initiating robust type I interferon responses in mammalian cells (Shaji et al. 2024). Its unique 2'-5'/3'-5' phosphodiester linkages distinguish it from bacterial CDNs and confer high specificity for human STING (IFG-1, 2023). Encapsulation in lipid nanoparticles enhances cytosolic delivery and anti-tumor efficacy in preclinical models. APExBIO offers 2'3'-cGAMP (sodium salt), SKU B8362, as a highly pure, workflow-optimized reagent for immunology, oncology, and antiviral research (product page). The product is water-soluble (≥7.56 mg/mL), stable at -20°C, and suitable for assay integration.

Biological Rationale

2'3'-cGAMP (cyclic [G(2',5')pA(3',5')p]) is a second messenger produced by cyclic GMP-AMP synthase (cGAS) upon sensing cytosolic double-stranded DNA (dsDNA) in mammalian cells. This mechanism functions as a primary sensor for pathogenic DNA, triggering the STING (stimulator of interferon genes) pathway and subsequent type I interferon (IFN-β) responses (Shaji et al. 2024). The discovery of 2'3'-cGAMP established a direct molecular link between DNA sensing and innate immunity in vertebrates. The endogenous production of 2'3'-cGAMP, as opposed to bacterial cyclic dinucleotides, ensures species-optimized signaling and avoids cross-reactivity. High-affinity binding to STING (Kd = 3.79 nM) distinguishes 2'3'-cGAMP from alternative CDNs, making it the principal ligand for STING-mediated immune activation (Pepbridge).

Mechanism of Action of 2'3'-cGAMP (sodium salt)

2'3'-cGAMP (sodium salt) is synthesized when mammalian cGAS detects cytosolic dsDNA. The enzyme uses ATP and GTP to generate 2'3'-cGAMP via non-canonical 2'-5' and 3'-5' linkages (Shaji et al. 2024). The resulting cyclic dinucleotide diffuses to the endoplasmic reticulum, where it directly binds to the ligand-binding domain of STING. Upon binding, STING undergoes conformational change and translocates from the ER to the Golgi apparatus. This trafficking event recruits TANK-binding kinase 1 (TBK1), leading to phosphorylation and activation of interferon regulatory factor 3 (IRF3). Activated IRF3 translocates to the nucleus, promoting transcription of type I interferon genes such as IFN-β. The downstream effect is a potent antiviral and immunostimulatory response. Notably, 2'3'-cGAMP's unique linkage pattern confers higher affinity and selectivity for human STING compared to bacterial CDNs (e.g., c-di-GMP, c-di-AMP), which show reduced potency in human cells (DisodiumSalt). This precision makes 2'3'-cGAMP (sodium salt) an indispensable research tool for dissecting cGAS-STING signaling.

Evidence & Benchmarks

• 2'3'-cGAMP (sodium salt) binds human STING with a dissociation constant (Kd) of 3.79 nM, the highest affinity reported for a natural CDN agonist (Shaji et al. 2024).
• Encapsulation of 2'3'-cGAMP in lipid nanoparticles (LNPs) increases cytosolic delivery and enhances antitumor activity in syngeneic mouse models of pancreatic cancer (Shaji et al. 2024).
• Intratumoral administration of 2'3'-cGAMP induces robust type I interferon and chemokine responses, stimulating both innate and adaptive immunity (Shaji et al. 2024).
• 2'3'-cGAMP (sodium salt) is highly water-soluble (≥7.56 mg/mL in H₂O) and remains stable at -20°C, facilitating reproducible experimental workflows (APExBIO).
• Compared to other cyclic dinucleotides, 2'3'-cGAMP elicits stronger IFN-β induction and more pronounced tumor microenvironment remodeling (IFG-1).

Applications, Limits & Misconceptions

2'3'-cGAMP (sodium salt) is widely employed as a gold-standard STING agonist in cancer immunotherapy, antiviral research, and inflammation studies. It enables high-sensitivity interrogation of cGAS-STING signaling in both in vitro and in vivo models. The reagent is critical for screening novel STING modulators and for modeling innate immune responses to cytosolic DNA. In cancer biology, 2'3'-cGAMP facilitates the transformation of 'cold' tumors (e.g., pancreatic adenocarcinoma) into immunologically 'hot' microenvironments, promoting T cell infiltration and anti-tumor immunity (Shaji et al. 2024).

This article advances the mechanistic and benchmarking context beyond prior summaries (e.g., Pepbridge, which focuses on structural properties) and updates translational guidance in light of recent nanoparticle delivery breakthroughs (GDC0068).

Common Pitfalls or Misconceptions

• 2'3'-cGAMP (sodium salt) is membrane-impermeable and requires active delivery (e.g., electroporation, nanoparticles) for intracellular targeting. Passive addition to cell culture media typically yields low efficacy (Shaji et al. 2024).
• It selectively activates STING and does not directly stimulate other DNA sensors (e.g., AIM2, DAI, TLR9). Cross-pathway effects are indirect and context-dependent.
• Species-specific differences exist: 2'3'-cGAMP is potent in human and mouse STING but may have reduced activity in certain non-mammalian systems (Pepbridge).
• It is not suitable for use in ethanol or DMSO due to insolubility; only water-based buffers are recommended (APExBIO).
• Long-term storage above -20°C may compromise stability; repeated freeze-thaw cycles should be minimized.

Workflow Integration & Parameters

2'3'-cGAMP (sodium salt) from APExBIO (SKU B8362) is supplied as a solid, disodium salt (C20H22N10Na2O13P2; 718.37 Da). For experimental use, dissolve in sterile water to a minimum of 7.56 mg/mL. Avoid organic solvents. For cellular assays, delivery can be achieved via electroporation, lipid-mediated transfection, or encapsulation in nanoparticles (Shaji et al. 2024). Typical working concentrations range from 0.1–10 μM, but optimization by cell type and assay readout is required. Store aliquots at -20°C to preserve activity. The B8362 kit enables high-throughput screening of novel STING modulators and provides a reference standard for cGAS-STING pathway interrogation (DUP753), offering more workflow-specific guidance than general overviews.

Conclusion & Outlook

2'3'-cGAMP (sodium salt) is the premier endogenous STING agonist for dissecting innate immune pathways and modeling type I interferon responses. Its high affinity, water solubility, and stability make it essential for immunology, oncology, and antiviral research. Recent advances in nanoparticle-based delivery are expanding its translational potential in cancer immunotherapy. APExBIO's formulation (SKU B8362) ensures reproducibility and compatibility with diverse experimental platforms. Ongoing research will clarify its role in modulating tumor microenvironments and guiding next-generation immunotherapeutic strategies (Shaji et al. 2024).

For further details and ordering, visit the 2'3'-cGAMP (sodium salt) product page.