Human genetics guides the discovery of novel CARD9 inhibitors with in vitro and in vivo anti-inflammatory activity

Human genetic association studies highlight key genes involved in disease pathology, yet targets identified by these analyses often fall outside the traditional definitions of druggability. A rare, truncated variant of the scaffold protein CARD9 is linked with protection from Crohn’s disease, prompting us to pursue the development of inhibitors that might similarly modulate innate inflammatory responses. Using a phased approach, we first identified a ligandable site on CARD9 using a structurally diverse DNA-encoded library and defined this site in detail through X-ray crystallography. Building upon this, a subsequent ligand displacement screen identified additional molecules that uniquely engage CARD9 and prevent its assembly into scaffolds needed to nucleate a signalosome for downstream NFκB induction. These inhibitors suppressed inflammatory cytokine production in dendritic cells and a humanized CARD9 mouse model. Collectively, this study illustrates a strategy for leveraging protective human genetic variants and chemical biology to tackle challenging targets for dampening inflammation.