A review, with 14 references, is given on the synthetic route, pharmacol. action, and clin. research of a cyclin-dependent protein kinases 4/6 inhibitor, ribociclib.The incidence of breast cancer is increasing year by year, and has become a major public health problem in the world.Cycle dependent protein kinase(CDK) 4/6 inhibitor can block cell cycle in G1 phase, which can inhibit tumor growth.Ribociclib is a highly specific protein kinases 4/6 inhibitor, which can inhibit D1/CDK4 and D3/CDK6 cell cycle, and has potential antitumor activity.The results of clin. trials indicate that ribociclib has clin. efficacy in treatment of breast cancer, melanoma, non-small cell lung cancer, teratoma, liposarcoma, and glioblastoma.