RU.521 (2262452-06-0) is an inhibitor of cyclic GMP-AMP synthase (cGAS), an important innate immune system sensor of foreign cytoplasmic double-stranded DNA.1,2 IC50 = 0.70 μM in dsDNA-stimulated RAW macrophages1 and ~0.80 μM in wild type human THP-1 cells2. It is selective for cGAS with no targeting of IFNB1 protein, interferon receptors, or downstream signaling components of the JAK/STAT pathway. RU.521 was able to significantly increase cardiac output in a mouse model of sepsis.3 Active in both mouse and human cell lines.
The potency and selectivity of a chemically improved inhibitor, RU.521, in cellular assays show that while it inhibits cGAS-mediated interferon upregulation, it has reduced to no effect on inflammatory pathways independent of cGAS. Furthermore, RU.521 suppresses the chronically elevated levels of type I interferon observed in primary macrophages from Trex1 null mice, a model of AGS. Crystal structures show that RU.521 occupies the catalytic pocket of murine cGAS, thus interfering with the entry of its ATP and GTP substrates. RU.521 inhibits cytoplasmic DNA-dependent upregulation of IRF3-dependent transcriptional targets only in the presence of an intact cGAS-STING pathway[1-2].
Vincent et al. (2017), Small molecule inhibition of cGAS reduces interferon expression in primary macrophages from autoimmune mice; Nat. Commun. 8 750
Wiser et al. (2020), Small molecule inhibition of human cGAS reduces total cGAMP output and cytokine expression in cells; Sci. Rep. 10 7604
Xu et al. (2020), Small molecule inhibition of cyclic GMP-AMP synthase ameliorates sepsis-induced cardiac dysfunction in mice; Life Sci. 260 118315
[1] Jessica Vincent. “Small molecule inhibition of cGAS reduces interferon expression in primary macrophages from autoimmune mice.” Nature Communications (2017): 750.
[2] Caroline Wiser. “Small molecule inhibition of human cGAS reduces total cGAMP output and cytokine expression in cells.” Scientific Reports (2020): 7604.
