The sulfate salt of vinblastine, a natural alkaloid isolated from the plant Catharanthus roseus (Madagascar periwinkle) with antineoplastic properties. Vinblastine disrupts microtubule formation and function during mitosis and interferes with glutamic acid metabolism. or A drug used to treat several types of cancer, including breast cancer and a type of gestational trophoblastic tumor that have not gotten better with other treatment, lymphoma, testicular cancer, Kaposi sarcoma, and mycosis fungoides. It is also being studied in the treatment of other types of cancer. Vinblastine sulfate blocks cell growth by stopping cell division and may kill cancer cells. It is a type of vinca alkaloid and a type of antimitotic agent. Also called Velban and Velsar.