STING
STING (Stimulator of Interferon Genes).

STING is a transmembrane protein that is found in the endoplasmic reticulum. When cyclic dinucleotides are directly bound to it, the protein changes its conformation, which sets off a chain of events that includes the activation of TBK1, the phosphorylation of IRF-3, and the generation of IFN-β and other cytokines. One potential therapeutic approach to support wide tumor-initiated T cell priming toward tumor antigen repertoire is the direct activation of the STING pathway[1].

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The ADU-S100 enantiomer has significantly less or no activity in activating the STING pathway compared to the parent compound. It fails to efficiently induce TBK1 activation, IRF-3 phosphorylation, or downstream cytokine (e.g., IFN-beta) production in cell-based assays.

In animal models, this enantiomer does not induce the regression of established tumors or generate systemic immune responses, unlike the active ADU-S100. It serves as a critical negative control to confirm that biological effects are due to stereospecific STING activation.

In a non-cellular binding assay, recombinant human STING protein is immobilized on a sensor chip. Varying concentrations of the ADU-S100 enantiomer are flowed over the chip. Binding affinity (KD) is measured using Surface Plasmon Resonance (SPR). The enantiomer shows minimal or no binding compared to the active ADU-S100.

THP-1 (human monocytic) cells are seeded and treated with varying concentrations of the ADU-S100 enantiomer. After 6-24 hours, culture supernatants are harvested. The concentration of human IFN-beta is measured by ELISA. The enantiomer induces negligible cytokine production compared to the active STING agonist.

C57BL/6 mice bearing established B16-F10 melanomas are treated with intratumoral (IT) injections of the ADU-S100 enantiomer (e.g., 25 ug) or vehicle on days 1-5. Tumor growth is monitored every 2-3 days. The enantiomer treatment group shows no significant tumor growth inhibition compared to the vehicle control.

PK properties are not relevant for a negative control. The enantiomer is chemically identical to ADU-S100, so it would have similar absorption and distribution properties. However, its lack of target engagement ensures it does not elicit the pharmacodynamic effects of the active compound.

No toxicity studies are conducted for the enantiomer specifically. As an inactive molecule, it is expected to have no specific toxicological liabilities beyond those of the vehicle. It is used to demonstrate that the toxicity of the active compound is due to on-target STING pharmacology.

[1]. Corrales L, et al. Direct Activation of STING in the Tumor Microenvironment Leads to Potent and Systemic Tumor Regression and Immunity. Cell Rep. 2015 May 19;11(7):1018-30.

ADU-S100 (MIW815) is a synthetic cyclic dinucleotide (CDN) agonist (activator) that activates the interferon gene-stimulating factor (STING) receptor. The STING receptor is a key receptor for activating the innate (endogenous) immune system. ADU-S100 (MIW815) activates all known human and mouse STING receptors and effectively induces the expression of cytokines and chemokines, thereby generating a potent and durable antigen-specific T cell-mediated immune response against cancer cells. MIW815, a STING-activating cyclic dinucleotide agonist listed in the DrugBank database, is a synthetic cyclic dinucleotide (CDN) and an agonist of the interferon gene-stimulating factor protein (STING; transmembrane protein 173; TMEM173), possessing potential immunomodulatory and antitumor activity. After intratumoral injection, the STING agonist MIW815 binds to STING and activates the STING-mediated signaling pathway. This activates the immune response by activating certain immune cells, including dendritic cells (DCs), which in turn induces the expression of cytokines and chemokines, ultimately leading to an antigen-specific T cell-mediated immune response against cancer cells. STING is a transmembrane protein that can activate immune cells in the tumor microenvironment and plays a key role in the activation of the innate immune system.

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Tumor-initiated spontaneous T cell initiation depends on IFN-β produced by tumor-resident dendritic cells. Based on recent observations that IFN-β expression depends on the activation of the host STING pathway, we hypothesize that direct activation of the STING pathway by intratumoral (IT) injection of a specific agonist will produce an effective antitumor therapeutic effect. After a proof-of-concept study using the mouse STING agonist DMXAA showed significant therapeutic effects, we synthesized cyclic dinucleotide (CDN) derivatives that can activate all human STING alleles and mouse STING. Intrathecal injection of STING agonists significantly inhibited established tumors in mice and produced a strong systemic immune response that could clear distant metastases and provide durable immune memory. Synthetic CDN has great potential for translational application as a cancer therapeutic agent. [1]

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ADU-S100 (MIW815) is a synthetic CDN specifically designed to activate all known human and mouse STING alleles. It was a pioneering STING agonist that entered clinical trials for solid tumors. The enantiomer is an essential research tool for validating the specificity of STING-related findings. ADU-S100 activates STING, leading to TBK1 activation, IRF-3 phosphorylation, and induction of IFN-beta and pro-inflammatory cytokines, culminating in an anti-tumor T-cell response.

C20H30N12O10P2S2

724.60

ADU-S100 disodium salt;1638750-95-4;ADU-S100 ammonium salt;1638750-96-5;ADU-S100;1638241-89-0

Typically exists as solid at room temperature

MIW815 enantiomer ammonium salt; ADU-S100 enantiomer ammonium salt;ML RR-S2 CDA enantiomer ammonium salt

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO :~50 mg/mL (~69.00 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (3.45 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (3.45 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (3.45 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)