Targeting the cGAS-STING Pathway Using a Homogenous, HTS Compatible Transcreener cGAS Assay

Discover cGAS Inhibitors with the Transcreener cGAMP cGAS Assay

The Transcreener cGAMP cGAS Assay directly measures cyclic GMP-AMP (cGAMP) produced by cyclic GMP-AMP synthase (cGAS, C6orf150, 2'3'-cGAMP Synthase). By measuring the production of cGAMP researchers can effectively determine the activity of the cGAS enzyme. The assay provides a powerful tool to screen entire compound libraries for cGAS modulators to help find new therapeutics targeting the cGAS-STING pathway.

cGAS is an Important Messenger in the STING Pathway

The presence of DNA in the cytosol of eukaryotic cells is an indicator of infection or cellular damage, and it elicits a robust immune response, driven by type I interferon (IFN) induction.  cGAS is an exquisitely sensitive sensor for double-stranded DNA in the cytoplasm.  Binding of DNA activates the enzyme to produce a unique cyclic dinucleotide second messenger, cGAMP, which acts as an agonist for the STING (stimulator of interferon genes) receptor, leading to induction of a type I interferon response.

cGAS STING Pathway

Direct Detection of cGAMP to Measure cGAS Enzymatic Activity

cGAS Assay Schematic FP
cGAS Assay Schematic TR-FRET


  • Measure Enzymatic Activity of cGAS
  • Screen Compound Libraries for cGAS inhibitors
  • Quantify Inhibitor Potency
  • Determine Inhibitor-cGAS Residence Time


  • Direct detection of unlabeled cGAMP
  • Easy to use, homogenous, one step format
  • Robust Assay Z’ > 0.7 under initial velocity conditions
  • Far-red fluorescent readouts minimize compound interference
  • A safe, non-radioactive method
  • Available in FP or TR-FRET readouts

Easy-to-Use, Mix-and-Read, HTS-Ready Assay

The Transcreener cGAS Assay is in a simple, HTS-ready, mix-and-read format. Run your enzyme reaction, add Transcreener reagents, and read your plates. The assay is compatible with 96, 384, and 1536-well formats.

Detection of cGAMP Under cGAS Initial Velocity

The assay demonstrates linearity when raw data is converted to cGAMP using a standard curve. cGAS is activated by double-stranded DNA and requires ATP and GTP substrates for the production of cGAMP.

Full-Length Human cGAS Titration

cGAS Enzyme Titration

Linear Response

Screen for Inhibitors & Perform SAR

The Transcreener cGAS Assay is designed for screening compound libraries in a high throughput format. Follow up SAR can also be performed using the assay to determine inhibitor potency with ease.

1600 Compound Pilot Screen

Acquire Accurate Dose Response Measurements

cGAS Inhibitor Dose Response Curves

Illustrates DNA & Substrate Dependance of the cGAS Enzyme

The assay accurately demonstrates the characteristics of the cGAS enzyme. Double-stranded DNA activates the enzyme which generates cGAMP in the presence of both GTP and ATP. A 45 base pair ISD (interferon stimulatory DNA) and a 60 base pair HSV (herpes simplex virus) DNA  both activate the enzyme. The assay has a high affinity to cGAMP and can detect even in the presence of other nucleotides.

cGAS Enzyme Activation by dsDNA

cGAS DNA Titration

Dependence on ATP and GTP

cGAS Enzyme Dependent on ATP and GTP

Outstanding Signal Stability

The assay exhibits 24 hours+ signal stability. Plate stability like this is vital for sizeable high throughput screens that take significant time to complete due to massive sample quantity.

Standard curves include ATP, GTP, dsDNA, and titration of cGAMP. The same plate was read at each time point.

cGAS Assay Signal Stability

cGAS Assay Services

Interested in moving your program forward, but don't want to bring an assay in-house? Our scientists can help! BellBrook scientists will use their extensive biochemistry and enzymology expertise to work with you and accelerate your cGAS program.

Assay Development Services

Lead Discovery Services Include:

  • Inhibitor Screening – To identify or confirm activity with the target.
  • Inhibitor Potency Profiling – Dose-response with target and/or related proteins. Fast IC50 results.
  • Residence Time Measurements – Determination of koff using ‘jump dilution’ enzymatic assay method.
  • Mechanism of Action Studies – Kinetic analysis to define the mode of inhibition.

Contact Us to Learn More

Please fill out the form below. We will respond quickly to get the conversation moving and learn how we can help. We keep things discrete, confidential, and professional.

Far-Red FP & TR-FRET Readouts Validated on Major Multimode Readers

Supplier Instrument FP Assays
TR-FRET Assays
bioteklogo TriStar²S LB 942 in review validated
Mithras² LB 943 in review validated
bioteklogo Cytation™ 5 validated validated
Cytation™ 3 validated validated
Cytation™ 1 validated validated
Synergy™ H1 validated validated
Synergy™ 2/H4/4 validated validated
Synergy™ HTX not capable not capable
Synergy™ Neo 2 validated validated
BMGLABTECH Logo POLARstar® Omega validated validated
FLUOstar® Omega not capable validated
PHERAstar® FSX validated validated
PHERAstar® Plus/FS validated validated
CLARIOstar® /Plus validated validated
MDS AT logo Analyst® GT/HT validated validated
Gemini® XPS/EM not capable not capable
SpectraMax® M2/M2e not capable not capable
SpectraMax® M5/M5e/FlexStation® 3 not capable validated
SpectraMax® Paradigm validated contact us
SpectraMax® iD3/iD5 in review validated
perkinElmerLogo EnVision®/EnVision® Xcite validated validated
tecanLogo Infinite® M1000/M1000Pro/Safire2™ validated validated
Infinite® M200 not capable not capable
Infinite® F500 validated validated
Infinite® F200/Ultraevolution contact us contact us
Spark™ 10M validated validated

What's Included

What You Will Need

Transcreener cGAMP cGAS Assay Kits

* For custom or bulk orders (over 100,000 wells) please contact us ( for a quote.

cGAS Enzyme Ordering Information

* For custom or bulk orders (over 100 μg) please contact us ( for a quote.