FDA Grants Accelerated Approval to Leukemia Drug

The US Food and Drug Administration (FDA) today approved Talon Therapeutics' Marqibo (vincristine sulfate liposome) to treat a rare subset of acute lymphoblastic leukemia (ALL).

In a 9 August press release, FDA said the drug is intended to treat adults with Philadelphia chromosome negative (Ph-) ALL, an aggressive form of blood and bone marrow cancer usually found in children. The condition affects approximately 6,000 patients in the US each year, making data collection difficult, but also allowing Marqibo to qualify for orphan drug status, which comes with extended marketing exclusivity.

Marqibo was approved using two safety trials of 83 patients each and one effectiveness trial using 65 patients. FDA said the data showed 15.4% of patients responded with complete or near-complete remission lasting a median of 28 days. 

100% Rate of Adverse Events

Seventy-five percent of patients experienced serious adverse events during the course of the efficacy trial, including low white blood cell count with fever, low blood pressure, respiratory distress and cardiac arrest. Other, less serious adverse events were also observed in patients as well. The drug's label notes adverse reactions were observed in 100% of patients.

As a result of the serious risks, Marqibo will be required to carry a Boxed Warning and will only be permitted to be administered through an IV line, "Because it is deadly if administered in other ways, such as into the spinal fluid," said FDA.

According to the drug's approved label, Marqibo is difficult to prepare, requiring a 26-step process that takes between 60 and 90 minutes of uninterrupted aseptic preparation. Even then, the drug cannot be combined with other drugs due to a high risk of overdose, for which there is no antidote.

The company will be required to conduct additional clinical testing under the terms of FDA's accelerated approval program.