The FDA approved Talon Therapeutics’ Marqibo (vincristine sulfate liposome injection) to treat adults with a rare type of leukemia called Philadelphia chromosome negative (Ph-) acute lymphoblastic leukemia (ALL), a rapidly progressing form of blood and bone marrow cancer that is more commonly diagnosed in children than adults.

Marqibo is approved for patients whose leukemia has relapsed two or more times, or whose leukemia has progressed following two or more regimens of anti-leukemia therapy. Marqibo contains vincristine, a commonly used anti-cancer drug, encased within a liposome, a drug delivery vehicle composed of material similar to that of cell membranes. It is administered via injection once a week by a health care professional.

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. The study objective was to determine the response rate to Marqibo, as either a complete remission (CR) or a complete remission with incomplete blood count recovery (CRi). Of 65 patients enrolled, 10 patients, or 15.4%, responded with either a CR or CRi. In the 10 patients achieving CR or CRi, the median duration of documented remission was 28 days. The median time to the first event of relapse, death or next therapy was 56 days.

The drugs most frequent serious adverse events were low white blood cell counts with fever, low blood pressure, respiratory distress and cardiac arrest. 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.  

Marqibo was an orphan drug and is approved under the FDA’s accelerated approval program.