Developments of Kinesin Spindle Protein Inhibitors as Antitumor Agents Based on the Five-membered Heterocycle Scaffolds

Kinesin spindle protein (KSP) plays an essential role in centrosome separation and formation of the bipolar mitotic spindle. Its exclusive involvement in the mitotic spindle of proliferating cells presents an opportunity for developing new anticancer agents with reduced side effects relative to antimitotics that target tubulin. Small molecule KSP inhibitors have demonstrated their potential as novel antimitotic agents. Several KSP inhibitors have progressed into clinical trials and many others are in preclinical developments. Recently, KSP inhibitors of wide structural diversity have appeared in literatures. This review will summarize the developments of KSP inhibitors based on the five-membered heterocycle scaffolds in recent 10 years. These small molecule KSP inhibitors were classified as dihydropyrazoles, dihydropyrroles, thiophenes, dihydrothiadiazoles, thiazoles and fused pyrroles, their structure-activity relationships were discussed.