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Murine cGAS inhibitor - InvitroFit™

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2 x 2 mg

5 x 2 mg


Inhibition of cGAS signaling by RU.521
Inhibition of cGAS signaling by RU.521

Specific inhibitor of murine cGAS

RU.521 is described as a small molecule inhibitor of cGAS (cyclic GMP-AMP synthase, cGAMP synthase)[1, 2]. cGAS is the primary sensor of cytosolic double-stranded DNA (dsDNA), a danger signal indicating possible disturbances in homeostasis caused by infection, sterile tissue damage, and/or cancer. cGAS signals through STING and TBK1 to activate the type I interferon (IFN).

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Mode of action:

In a healthy individual, cGAS senses the abnormal presence of cytosolic DNA such as during bacterial or viral infection. In some autoimmune diseases, cGAS can be constitutively activated by mislocalized self-DNA leading to high type I interferon (IFN) production. RU.521 has been demonstrated to reduce IFN production in vitro and ex vivo in models of autoimmune diseases, such as Aicardi-Goutières [1,2].
RU.521 more potently inhibits the activity of murine cGAS compared to human cGAS [2].

Key features:

  • Potent inhibitor of murine cGAS
  • InvitroFit™ grade: each lot is highly pure (≥95%) and functionally tested.


Learn more Read our review on cGAS.



1. Vincent J. et al., 2017. Small molecule inhibition of cGAS reduces interferon expression in primary macrophages from autoimmune mice. Nat Commun. 28(1):750.
2. Zhou W. et al., 2018. Structure of the human cGAS-DNA complex reveals enhanced control of immune surveillance. Cell. 174(2):300-311.


Dose-dependent inhibition of cGAS
Dose-dependent inhibition of cGAS

Effect of RU.521 on the response of RAW-Lucia™ ISG cells to cytosolic dsDNA. RAW-Lucia™ ISG cells were incubated with 1 μg/ml of cytosolic dsDNA (plasmid DNA delivered intracellularly using cationic lipid transfection) and increasing concentrations of RU.521. After overnight incubation, the IRF response was assessed by determining Lucia luciferase activity in the supernatant using QUANTI‑Luc™. Data are shown as percentage (%) activity.

Assessment of inhibition by RU.521
Assessment of inhibition by RU.521

RU.521 primarily inhibits cGAS activity.
A: RAW-Lucia™ ISG cells were incubated with 1 μg/ml of cytosolic G3-YSD (Y-form DNA) and plasmid DNA in the presence or absence of 2.5 μg/ml of RU.521. G3-YSD and the plasmid DNA were delivered into the cytoplasm using cationic lipid transfection.
B: RAW‑Lucia™ ISG-KO-cGAS cells were incubated with 10 μg/ml of 2’3’-cGAMP in the presence or absence of 2.5 μg/ml of RU.521. After overnight incubation, the IRF response was assessed using QUANTI‑Luc™ and expressed as percentage (%) activity.

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Working concentration: 200 ng/ml (482 nM) to 20 μg/ml (48.2 μM) for cell culture assays.

Solubility: 2 mg/ml (4.82 mM) in DMSO

Formula: C19H12Cl2N4O3

Molecular weight: 415.23 g/mol

Quality control:

  • Purity ≥ 95% (UHPLC).
  • The absence of bacterial contamination (e.g. lipoproteins and endotoxins) has been confirmed using HEK-Blue™ TLR2 and HEK‑Blue™ TLR4 cells.
  • The inhibitory activity has been validated using cellular assays.
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RU.521 is available in two quantities:

  • inh-ru521-2: 2 x 2 mg
  • inh-ru521-5: 5 x 2 mg

RU.521 is shipped at room temperature.

Upon receipt, store at -20°C.


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Cyclic GMP-AMP synthase (cGAS, cGAMP synthase) is a critical cytosolic DNA sensor that triggers innate immune responses through the production of type I interferons (IFNs) [1]. In response to cytosolic double‑stranded DNA (dsDNA), cGAS produces the cyclic dinucleotide (CDN) 2’3’-cGAMP.
CDNs bind directly to STING, leading to TBK1‑IRF3-mediated activation of IFN-stimulated response elements (ISRE) in the promoters of IFN-stimulated genes (ISG). The most potent agonist of human STING is 2’3’-cGAMP [2,3].



1. Sun L. et al., 2013. Cyclic GMP-AMP synthase is a cytosolic DNA sensor that activates the type I interferon pathway. Science 339(6121):786-91.
2. Gao P. et al., 2013. Cyclic [G(2’,5’)pA(3’,5’)p] is the metazoan second messenger produced by DNA-activated cyclic GMP-AMP synthase. Cell. 153(5):1094-107.
3. Ablasser A. et al., 2013. cGAS produces a 2’-5’-linked cyclic dinucleotide second messenger that activates STING. Nature. 498(7454):380-4.


Chemical structure of RU.521:


Chemical structure of RU.521

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