RU.521 (RU3205217) is a potent dsDNA inhibitor (IC50 : 700 nM), inhibition of the dsDNA pathway by RU.521 requires the presence of cGAS.

dsDNA:700 nM

Treatment of primary BMDMs with RU.521 or its analogs reduced IFNB1 expression in mice, indicating their effectiveness in suppressing intrinsic DNA-dependent, constitutively-activated type I interferon expression in cells deficient of a cytoplasmic DNA exonuclease.

Small-molecule compounds were serially diluted to concentrations spanning the range tested in the response curves were added to 6.7?×?10^5 RAW-Blue macrophages plated 16?h prior in 96-well dishes, then harvested 72?h after compound addition. ATP was measured using CellTiter Glo Viability Assay using 50?μM Tamoxifen as a positive control for cytotoxicity. Viability values were generated using vehicle (DMSO) or the first dose as 100% and Tamoxifen as 0%. Outliers were removed.

the chronically elevated levels of cytokines observed in Trex1 null mice are a consequence of constitutively activated cGAS, due to the inability to eliminate aberrantly localized self-DNA. We harvested BMDMs from 6–8-week old Trex1 ?/? mice, treated them with each compound, and measured expression levels of IFNB1 by quantitative reverse transcription PCR (qRT-PCR). Treatment of primary BMDMs with RU.521 or its analogs reduced IFNB1 expression, indicating their effectiveness in suppressing intrinsic DNA-dependent, constitutively-activated type I interferon expression in cells deficient of a cytoplasmic DNA exonuclease.