Recent Advances in Heterocyclic Tubulin Inhibitors Targeting the Colchicine Binding Site.

Microtubules are involved in many critical cellular processes including cell division, cell shape maintenance, vesicle transportation and motility regulation. Disruption of tubulin dynamics is a well-validated cancer drug target with several FDA approved, highly efficacious tubulin inhibitors targeting the taxane or the vinca binding sites. Despite the tremendous successes for these clinical tubulin inhibitors, their limitations are also apparent, particularly in the development of transporter mediated drug resistance. While currently there are no FDA approved inhibitors targeting the colchicine binding site in tubulin, extensive preclinical studies have suggested that colchicine binding site inhibitors (CBSIs) have significantly less susceptibility to transporter medicated drug resistance. The presence of one or more heterocyclic moieties is often critical for the antiproliferative activities for most of these CBSIs. This article aims to review the structures and antiproliferative activities of most recently developed heterocyclic CBSIs from 2013 to present. We focus this review on compounds that are designed based on the CA-4, chalcone and PTOX scaffolds which are well established to interact with the colchicine binding site in tubulin.