Abstract This Letter details the synthesis and evaluation of imidazo [4, 5-b] pyridines as inhibitors of B-Raf kinase. These compounds bind in a DFG-in, αC-helix out conformation of B-Raf, which is a binding mode associated with significant kinase selectivity. Structure– activity relationship studies involved optimization of the ATP-cleft binding region of these molecules, and led to compound 23, an inhibitor with excellent enzyme/cell potency, and ...