K-858

A potent, selective inhibitor of mitotic kinesin Eg5 ATPase activity with IC50 of 1.3 uM; displays >150-fold more selective for Eg5 than other members of the kinesin superfamily; induces mitotic arrest, apoptosis, and cell growth inhibition through the activation of the Mad2-mediated spindle checkpoint, and has no effect on microtubule polymerization; exhibits potent antitumor activity in xenograft models of cancer, and induces the accumulation of mitotic cells with monopolar spindles in tumor tissues.Breast Cancer Preclinical.