Vincristine is also the active ingredient in Vincasar PFS® (vincristine). Marqibo is a form of vincristine that is contained in tiny particles of fat (liposomes). Marqibo stays in the body longer than Vincasar PFS, and reaches higher levels inside tumors (compared to certain other cells, such as nerve cells). It is thought to be more effective than Vincasar PFS and to have fewer side effects.
However, it is important to note that Vincasar PFS is available in generic form, while Marqibo is not.