Microtubules (tubulin)

Class

Topical nanoparticle paclitaxel ointment

Microtubules are dynamic filaments built from repeating units of the protein tubulin. They form the mitotic spindle that pulls duplicated chromosomes apart during cell division, and they also serve as internal scaffolding and transport tracks in nearly all cells. Because rapid, repeated division is a hallmark of cancer, drugs that interfere with microtubule function can selectively harm tumor cells. Taxanes, the class this mechanism belongs to, bind tubulin and stabilize microtubules so they cannot disassemble normally. This locks the mitotic spindle in place, preventing dividing cells from completing mitosis and triggering programmed cell death. The therapeutic rationale for a topical, nanoparticle-based formulation is to concentrate this cytotoxic effect at accessible superficial or cutaneous tumor sites while limiting the drug's entry into the general circulation, where microtubule disruption in normal dividing tissues causes much of the toxicity associated with systemic taxane therapy. Nanoparticle carriers are used to help the lipophilic drug penetrate skin layers and reach target tissue in adequate concentration. This mechanism is broadly relevant across oncology, since microtubule-targeting agents are used against many solid tumor types, and a localized route of delivery is one strategy for extending their use to skin-confined disease.