1H-pyrazolo[3,4-b]pyridine inhibitors of cyclin-dependent kinases: Highly potent 2,6-difluorophenacyl analogues

Structure-activity studies of 1H-pyrazolo[3,4-b]pyridine 1 have resulted in the discovery of potent CDK1/CDK2 selective inhibitor 21h, BMS-265246 (CDK1/cycB IC(50)=6 nM, CDK2/cycE IC(50)=9 nM). The 2,6-difluorophenyl substitution was critical for potent inhibitory activity. A solid state structure of 21j, a close di-fluoro analogue, bound to CDK2 shows the inhibitor resides coincident with the ATP purine binding site and forms important H-bonds with Leu83 on the protein backbone.