An IRAK4 inhibitor (IC50 = 0.2 nM); selective for IRAK4 over a panel of 268 kinases at 200 nM but also inhibits IRAK1, MNK2, LRRK2, Clk4, and CK1γ1 by >70% at 200 nM; reduces DNA secretion from R-837-stimulated primary human neutrophils and decreases R-848-induced IRF5 nuclear translocation in primary human PMBCs at 100 nM; decreases paw volume in a rat model of collagen-induced arthritis at 100 mg/kg once per day; reduces serum levels of anti-dsDNA, anti-SSA, and anti-RNP antibodies and decreases kidney glomerular tuft area in a mouse model of pristane-induced SLE