5-Iodo-indirubin-3'-monoxime is a potent GSK-3β, CDK5/P25 and CDK1/cyclin B inhibitor, competing with ATP for binding to the catalytic site of the kinase, with IC50s of 9, 20 and 25 nM, respectively[1]. GSK-3β|9 nM (IC50)|Cdk5/p25|20 nM (IC50)|Cdk1/cyclin B|25 nM (IC50)
[1]. Leclerc S, et al. Indirubins inhibit glycogen synthase kinase-3 beta and CDK5/p25, two protein kinases involved in abnormal tau phosphorylation in Alzheimer's disease. A property common to most cyclin-dependent kinase inhibitors• J Biol Chem. 2001 Jan 5;276(1):251-60.