Novel arylazopyrazole inhibitors of cyclin-dependent kinases.

Here, we describe new 4-arylazo-3,5-diamino-1H-pyrazole derivatives developed from CAN508, one of the first inhibitors to show preference for transcriptional regulator cyclin-dependent kinase 9. By substituting nitrogen in the pyrazole ring and employing a heteroatom in the 4-aryl ring, we obtained more potent derivatives differing in their CDK-selectivity profiles. The antiproliferative and anti-CDK kinase activities of the novel arylazopyrazoles were examined. The cellular effect of compound IVc was studied on MCF-7 cells synchronized by various methods and compared with other selective CDK inhibitors. The results demonstrated that IVc shows a preference for CDK4 and CDK1. In contrast to cytostatic effects induced by IVc in MCF-7 and K562 cells, we observed apoptotic activities in the RPMI-8226 cell line, which were confirmed by detecting active caspases by different biochemical assays.