Vinblastine

Vinblastine is an antimicrotubule drug used to treat certain kinds of cancer, including Hodgkin's lymphoma, non-small cell lung cancer, breast cancer, head and neck cancer, and testicular cancer. It is also used to treat Langerhan cell histiocytosis.

History
Vinblastine was first isolated by Robert Noble and Charles Thomas Beer from the Madagascar periwinkle plant. Vinblastine's utility as a chemotherapeutic agent was first discovered when it was crushed into a tea. Consumption of the tea led to a decreased number of white blood cells; therefore, it was hypothesized that vinblastine might be effective against cancers of the white blood cells such as lymphoma.

Pharmacology
Vinblastine is a vinca alkaloid and a chemical analogue of vincristine. It binds tubulin, thereby inhibiting the assembly of microtubules. It is M phase cell cycle specific since microtubules are a component of the mitotic spindle and the kinetochore which are necessary for the separation of chromosomes during anaphase of mitosis. Toxicities include bone marrow suppression (which is dose-limiting), gastrointestinal toxicity, potent vesicant (blister-forming) activity, and extravasation injury (forms deep ulcers).

Vinblastine paracrystals may be composed of tightly-packed unpolymerized tubulin or microtubules.

Mechanism of Action
Microtubule disruptive drugs like vinblastine, colcemid, nocodazole have been reported to act by two mechanisms. At very low concentrations they suppress microtubule dynamics and at higher concentrations they reduce microtubule polymer mass. Recent findings indicate that they also produce microtubule fragments by stimulating microtubule minus-end detachment from their organizing centers. Dose-response studies further indicate that enhanced microtubule detachment from spindle poles correlate best with cytotoxicity.

Indications
Vinblastine is a component of a number of chemotherapy regimens, including ABVD for Hodgkin lymphoma. It is also used to treat histiocytosis according to the established protocols of the Histiocytosis Association of America.