Cladophorol-A is an inhibitor of cyclic GMP-AMP synthase

Cyclic guanosine monophosphate (GMP)-adenosine monophosphate (AMP) synthase (cGAS) is an enzyme sensor of double-stranded DNA (dsDNA) that serves to trigger activation of the cGAS-stimulator of interferon genes (STING) pathway. Excessive activation of this pathway has been demonstrated to contribute to various forms of inflammatory disease. As such, cGAS has arisen as a potential therapeutic target with broad potential applications. Using a pathway-targeted cell-based screening approach, we identified the natural product Cladophorol-A as a new class of non-cytotoxic cGAS inhibitor (cell-based IC₅₀ = 370 nM). An X-ray co-crystal structure at 2.75 Å resolution revealed that Cladophorol-A inhibits cGAS by binding to its active site within the conserved adenosine nucleobase binding site.