antimitotic

An antimitotic stops a cell right in the act of dividing. When a cell splits, it builds a tiny scaffolding of fibres, the mitotic spindle, that grabs the chromosomes and hauls one full set into each daughter cell. An antimitotic drug sabotages that scaffolding, so the cell freezes mid-division and eventually dies.

These drugs act on microtubules, the protein cables that make up the spindle. Microtubules are dynamic, constantly growing and shrinking. Vinca alkaloids (like vincristine) bind tubulin and prevent microtubules from assembling, while taxanes (like paclitaxel) do the opposite, locking microtubules so rigidly they cannot break down. Either way the spindle cannot do its job, the cell arrests in mitosis (M phase), and apoptosis follows. This makes most antimitotics M-phase specific.

Because microtubules also serve as transport tracks inside nerve cells, a signature side effect is peripheral neuropathy: numbness, tingling and weakness in the hands and feet. This is dose-limiting for several agents and can be partly irreversible, so clinicians watch closely and may reduce the dose.