Novel 7H-pyrrolo[2,3-d]pyrimidine derivatives as potent and orally active STAT6 inhibitors

Signal transducers and activators of transcription 6 (STAT6) is an important transcription factor in interleukin (IL)-4 signaling pathway and a key regulator of the type 2 helper T (Th2) cell immune response. Therefore, STAT6 may be an excellent therapeutic target for allergic conditions, including asthma and atopic diseases. Previously, we reported 4-aminopyrimidine-5-carboxamide derivatives as STAT6 inhibitors. To search for novel STAT6 inhibitors, we synthesized fused bicyclic pyrimidine derivatives and identified a 7H-pyrrolo[2,3-d]pyrimidine derivative as a STAT6 inhibitor. Optimization of the pyrrolopyrimidine derivatives led to identification of 2-[4-(4-{[7-(3,5-difluorobenzyl)-7H-pyrrolo[2,3-d]pyrimidin-2-yl]amino}phenyl)piperazin-1-yl]acetamide (24, AS1810722) which showed potent STAT6 inhibition and a good CYP3A4 inhibition profile. Compound 24 also inhibited in vitro Th2 differentiation without affecting type 1 helper T (Th1) cell differentiation and eosinophil infiltration in an antigen-induced mouse asthmatic model after oral administration.