Characterization of a Small Molecule IRAK4 Kinase Inhibitor for the Treatment of Autoimmune and Inflammatory Diseases

IRAK4 is a key protein kinase in immune cells. It is responsible for initiating MyD88-dependent signaling from most Toll-Like Receptors (TLR) and Interleukin-1 Receptors (IL-1R), resulting in downstream production of pro-inflammatory cytokines. Hence, inhibitors of IRAK4 kinase activity represent valuable therapeutic tools to treat cytokine-driven autoimmune and inflammatory diseases. Through cell-based screening, we identified potent small molecule IRAK4 kinase inhibitors that block TLR4- and IL-1R-induced cytokine production with potencies less than 100nM. Our inhibitors exhibit good selectivity against a broad panel of kinases. In vivo, our lead compound decreases serum IL-6 in an acute mouse model of IL-1beta-induced cytokine release, demonstrating excellent pharmacokinetics properties. In addition, our IRAK4 inhibitor blocks monosodium urate crystals-induced peritonitis in mice, reduces paw swelling in the chronic rat model of collagen-induced arthritis, as well as the clinical score and overall inflammatory phenotype of mice in the imiquimod-induced psoriasis model. The in vitro and in vivo characterization of our lead candidate is promising and confirms IRAK4 as an attracting therapeutic target for the management of cytokine-driven diseases.