K858 is an ATP-uncompetitive inhibitor of Eg5 that is at least 150-fold more selective for Eg5 than other members of the kinesin superfamily. K858 induces mitotic arrest and growth inhibition through the activation of the Mad2-mediated spindle checkpoint. K858 induces mitotic cell death in Y cells but not in normal cells. K858 induces mitotic arrest, apoptosis, and cell growth inhibition and has no effect on microtubule polymerization.

K858 exhibits antitumor activity and induces mitotic arrest in a human tumor xenograft mouse model. K858 exhibits antitumor activity and induces mitotic arrest in human xenograft tumor models. [1]