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). 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

Measure Inhibitor Residence Time With a Simple Biochemical Assay

The Transcreener cGAS Assay can be used to measure drug-target residence time using the jump-dilution method. Because the assay can be used in kinetic mode, enzymatic activity can be measured as the enzyme regains activity once the inhibitor dissociates.

Get the Guide to Learn More About Residence Time

  • The basics of residence time and its importance to drug discovery
  • A comparison of methods used for residence time determination
  • Using the jump-dilution method with Transcreener biochemical assays
  • Data analysis used to accurately determine residence time
  • Examples of measuring residence time for kinases, phosphodiesterases, and glycosyltransferases

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

What's Included

Transcreener cGAMP cGAS Assay Kits

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

In addition to our cGAMP cGAS Assay, Bellbrook Labs also offers the following products to aid in the drug discovery process: