Design,Synthesis And Biological Evaluation Of Cyclin-dependent Kinase 2 Inhibitors Based On Pyrimidine Scaffold

The cyclin-dependent protein kinases(CDKs)are protein-serine/threonine kinases,and they are involved in various aspects of cell biology by binding to a cyclin protein,notably in cell-cycle control,transcription,metabolism and differentiation.Deregulation of the cell cycle,a significant hallmark of human cancer,is frequently associated with aberrant CDKs activity.The regulatory marketing of the CDK4/6 inhibitors has led to practice-changing outcomes in breast cancer treatment,which has increased interest in the field.But resistance is emerging as a major challenge.Besides,the literature indicates that the mechanisms of resistance to CDK4/6 inhibitors through upregulated activity of CDK2,which also plays an essential role in tumor growth in multiple cancer types with CDK2 dependency.Therefore,CDK2 has emerged as a promising therapeutic target in cancer and may help overcome treatment resistance.Several small-molecule CDK2 inhibitors identified to date have progressed to the clinical trials and all of them are nonselective.In order to discover selective and potent CDK2 inhibitors,a novel backbone structure bearing 2,4-diaminopyrimidine moiety was designed via retaining the common core from the purine and pyrimidine inhibitors.Based on our previous work,a 2,4-diaminopyrimidine derivative BZ-19,demonstrating potent activities against CDK2 and four cancer cell lines,deserved further optimization.Therefore,we have started a medicinal chemistry study on the lead compound BZ-19 to modify the crucial sites in positions C-5,C-2 and C-4 of pyrimidine skeleton.On the basis of previously synthesized compounds 12a-j,13a-x and 17a-k,29 target compounds 17b,17l-q,26a-h and 29a-n possessing 2,4-diaminopyrimidine groups,were further designed and synthesized,and the structures of target derivatives were characterized with spectroscopic techniques including 1H NMR,13C NMR and HRMS.In this paper,57 compounds 12a-j,13a-x,17a-q and 29a-f were evaluated for their in vitro antiproliferative activities against five human cancer cell lines including MDA-MB-231,MCF-7,HeLa,HCT116 and PC-3 using the MTT assay.Initial biological evaluation showed some of target compounds displayed potent antitumor activity in vitro against five cancer cell lines.Especially,the most promising compound 13s exhibited approximately potency with positive control AZD-5438 toward four cells including HeLa,HCT116,PC-3,and MDA-MB-231 with IC50 values of 0.45,0.70,0.92,1.80 μM,respectively.In addition,the most highly active compound 13s in this study also possessed potent CDK2-cyclinA inhibitory activities with IC50 values of 15.4 nM,which was comparable with that of positive control,and molecular docking studies revealed that the analogue bound efficiently with the CDK2 binding site.Further studies indicated that compound 13s could induce cell cycle arrest and apoptosis in a concentration-dependent manner.These encouraging findings suggest that the analogue 13s based on pyrimidine scaffold may has potential for clinical development as anticancer agents.