FDA grants accelerated approval for treatment of rare type of leukemia

FDA has approved vincristine sulfate liposome injection (Marqibo, Talon Therapeutics, http://www.marqibo.com/)for the treatment of adult patients with Philadelphia chromosome negative (Ph-) acute lymphoblastic leukemia (ALL) who have had at least two relapses or whose disease has progressed following two or more anti-leukemia therapies.

ALL is a rapidly progressing form of blood and bone marrow cancer that is more commonly diagnosed in children than in adults. According to the National Cancer Institute, an estimated 6,050 men and women will be diagnosed with ALL, and 1,440 will die from the disease this year.

This indication is based on overall response rate. Clinical benefit such as improvement in overall survival has not been verified. Marqibo is administered intravenously at a dose of 2.25 mg/m2 over 1 hour once every 7 days. Dosage recommendations for Marqibo are different than they are for non-liposomal vincristine sulfate.

"We are delighted that Marqibo will be available to a patient population with an underserved hematologic malignancy," said Steven R. Deitcher, MD, president, chief executive officer, and board member of Talon Therapeutics, in a company press release.

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 (15.4%) had 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 safety of Marqibo 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 the patients studied. The most common side effects observed during clinical studies include constipation, nausea, low blood-dcell counts, fever, nerve damage, fatigue, diarrhea, decreased appetite, and insomnia.

Prescribing information for Marqibo will carry a Boxed Warning alerting patients and healthcare 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 Marqibo has different dosage recommendations than vincristine sulfate injection alone.

To avoid overdose, it is important for healthcare professionals to verify the drug name and the dose before administration. Special requirements for preparation of the drug are detailed in the label (http://www.marqibo.com/).