The FDA has approved vincristine sulfate liposome injection (Marqibo) to treat adults with Philadelphia chromosome–negative acute lymphoblastic leukemia (ALL). Administered once a week, liposomal vincristine is approved for patients whose leukemia has relapsed two or more times, or whose leukemia has progressed following two or more regimens of antileukemia therapy.
The new drug is approved under the FDA’s accelerated approval program, which provides earlier patient access to promising new drugs while the manufacturer conducts additional clinical studies to confirm the drug’s clinical benefit and safe use. It also received orphan-product designation because it is intended to treat a rare disease.
The drug’s effectiveness was evaluated in a single clinical trial in adult patients whose leukemia had relapsed at least two times despite standard treatments, and who had at least one previous treatment response lasting at least 90 days. Of 65 patients enrolled, 10 patients (15.4%) responded with either a complete remission or complete remission with incomplete blood count recovery. In the 10 patients achieving either of those responses, the median duration of documented remission was 28 days. The median time to the first event (relapse, death, or next therapy) was 56 days.
The safety of liposomal vincristine was evaluated in two single-arm trials of 83 patients who received the clinical treatment regimen. Serious adverse events such as low white blood cell counts with fever, low blood pressure, respiratory distress, and cardiac arrest occurred in 76% of patients studied.
Prescribing information for Marqibo will carry a Boxed Warning alerting patients and health-care professionals that the drug must be administered only intravenously because it is deadly if administered in other ways, such as into the spinal fluid. The Boxed Warning also states that liposomal vincristine has different dosage recommendations than vincristine sulfate injection alone. To avoid overdose, it is important for health-care professionals to verify the drug name and the dose before administration. Special requirements for preparation of the drug are detailed in the label. ■