CDK/CRK inhibitor is an inhibitor of cyclin-dependent kinases (CDK) and CDK-related kinases (CRK) with IC50 values ranging from 9-839 nM in vitro. It is selective, exhibiting less than 20% inhibition of 60 non-CDK/CRK kinases, at a concentration of 1 μM. CDK/CRK inhibitor induces cell cycle arrest in the G1 phase, endoreduplication, and apoptosis in HCT116 cells. It exhibits broad anti-tumor activity with an average GI50 value of<10 nM for 60 tumorigenic cell lines. It also inhibits growth of non-cycling HCT116 cells with an IC50 value of 40 nM.