Discovery of 3,6-dihydroimidazo[4,5-d]pyrrolo[2,3-b]pyridin-2(1H)-one derivatives as novel JAK inhibitors.Because Janus kinases (JAKs) play a crucial role in cytokine-mediated signal transduction, JAKs are an attractive target for the treatment of organ transplant rejection and autoimmune diseases such as rheumatoid arthritis (RA).  To identify JAK inhibitors, we focused on the 1H-pyrrolo[2,3-b]pyridine derivative 3, which exhibited moderate JAK3 and JAK1 inhibitory activities.  Optimization of 3 identified the tricyclic imidazo-pyrrolopyridinone derivative 19, which exhibited potent JAK3 and JAK1 inhibitory activities (IC50=1.1 nM, 1.5 nM, respectively) with favorable metabolic stability.
C