K858 is primarily used in research settings as a potent inhibitor of kinesin spindle protein (KSP), a key player in cell division. By inhibiting KSP, it disrupts the formation of the mitotic spindle, effectively halting the proliferation of cells. This makes it a valuable tool in studying cancer biology, as it helps researchers understand the mechanisms of mitosis and explore potential therapeutic strategies for cancer treatment. Additionally, K858 is utilized in pharmacological studies to investigate the effects of mitotic inhibition on various cell types and to develop novel anti-cancer agents. Its ability to induce cell cycle arrest has also made it a subject of interest in drug discovery programs targeting rapidly dividing cells.