A form of the anticancer drug vincristine sulfate that is contained inside very tiny, fat-like particles. It may have fewer side effects and work better than vincristine. Marqibo is used to treat adults with acute lymphoblastic leukemia that is Philadelphia chromosome negative and has come back or has not gotten better with other treatment. It is also being studied in the treatment of other types of cancer. It is a type of vinca alkaloid and a type of antimitotic agent. Also called liposomal vincristine sulfate and vincristine sulfate liposome.