Vincristine, also known as leurocristine and sold under the brand name Oncovin among others, is a chemotherapy medication used to treat a number of types of cancer. This includes acute lymphocytic leukemia, acute myeloid leukemia, Hodgkin lymphoma, neuroblastoma, and small cell lung cancer among others. It is given intravenously. Most people experience some side effects from vincristine treatment. Commonly it causes a change in sensation, hair loss, constipation, difficulty walking, and headaches. Serious side effects may include neuropathic pain, lung damage, or low white blood cells which increases the risk of infection. Use during pregnancy may result in birth defects. It works by stopping cells from dividing properly. It is vital that it not be given intrathecally, as this may kill. Vincristine was first isolated in 1961. It is on the World Health Organization's List of Essential Medicines. It is a vinca alkaloid that can be obtained from the Madagascar periwinkle Catharanthus roseus.
Medical uses Vincristine is delivered via intravenous infusion for use in various types of chemotherapy regimens. Its main uses are in non-Hodgkin lymphoma as part of the chemotherapy regimen CHOP R-CVP, Hodgkin lymphoma as part of MOPP, COPP, BEACOPP, or the less popular Stanford V chemotherapy regimen, in acute lymphoblastic leukemia (ALL) as part of the VAMP regimen, and in treatment for nephroblastoma as well as the chemotherapy regimen VDC-IE for Ewing's sarcoma. It is also used to induce remission in ALL with dexamethasone and L-asparaginase, and in combination with prednisone to treat childhood leukemia. Vincristine is occasionally used as an immunosuppressant, for example, in treating thrombotic thrombocytopenic purpura (TTP) or chronic idiopathic thrombocytopenic purpura (ITP).
Side effects The main side effects of vincristine are chemotherapy-induced peripheral neuropathy, hyponatremia, constipation, and hair loss. Vincristine-induced neuropathy is the main dose-limiting side effect. Chemotherapy-induced peripheral neuropathy can be severe, and may be a reason to reduce or avoid using vincristine. The symptoms are progressive and enduring tingling numbness, pain and hypersensitivity to cold, beginning in the hands and feet and sometimes affecting the arms and legs. One of the first symptoms of peripheral neuropathy is foot drop: A person with a family history of foot drop and/or Charcot-Marie-Tooth disease (CMT) should avoid vincristine. A 2021 study has suggested that anakinra can reduce the neuropathy. Accidental injection of vinca alkaloids into the spinal canal (intrathecal administration) is highly dangerous, with a mortality rate approaching 100 percent. The medical literature documents cases of ascending paralysis due to massive encephalopathy and spinal nerve demyelination, accompanied by intractable pain, almost uniformly leading to death. Several patients have survived after aggressive and immediate intervention. Rescue treatments consist of washout of the cerebrospinal fluid and administration of protective medications. Children may do better following this injury. One child, who was aggressively treated at the time of the injection, recovered almost completely with only mild neurological deficits. A significant series of inadvertent intrathecal vincristine administration occurred in China in 2007 when batches of cytarabine and methotrexate (both often used intrathecally) manufactured by the company Shanghai Hualian were found to be contaminated with vincristine. The overuse of vincristine may also lead to drug resistance by overexpression of the p-glycoprotein pump (Pgp). There is an attempt to overcome resistance by the addition of derivatives and substituents to the vincristine molecule.
Mechanism of action Vincristine works partly by binding to the tubulin protein, stopping the tubulin dimers from polymerizing to form microtubules, causing the cell to be unable to separate its chromosomes during the metaphase. The cell then undergoes apoptosis. The vincristine molecule inhibits leukocyte production and maturation. A downside, however, to vincristine is that it does not only affect the division of cancer cells. It affects all rapidly dividing cell types, making it necessary for the very specific administration of the drug.
Chemistry The natural extraction of vincristine from Catharanthus roseus is produced at a percent yield of less than 0.0003%. For this reason, alternate methods to produce synthetic vincristine are being used. Vincristine is created through the semi-synthesis coupling of indole alkaloids vindoline and catharanthine in the vinca plant. It can also now be synthesized through a stereocontrolled total synthesis technique which retains the correct stereochemistry at C18' and C2'. The absolute stereochemistry at these carbons is responsible for vincristine's anticancer activity. The liposome encapsulation of vincristine enhances the efficacy of the vincristine drug while simultaneously decreasing the neurotoxicity associated with it. Liposome encapsulation increases vincristine's plasma concentration and circulation lifetime in the body, and allows the drug to enter cells more easily.
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