Leukemia Drug Approved-For the Second Time

The FDA approved Pfizer’s Mylotarg (gemtuzumab ozogamicin) for the treatment of adults with newly diagnosed acute myeloid leukemia whose tumors express the CD33 antigen (CD33-positive AML) or children aged two or older with CD33-positive AML who have experienced a relapse or who do not respond to initial treatment.

But this isn’t the first time Mylotarg has been FDA-approved. In May 2000, Mylotarg was approved with an accelerated approval designation. The drug was approved to treat recurrent AML in patients 60 and older who weren’t candidates for other chemotherapy. However, a post-approval clinical trial showed little clinical benefit and even a higher number of deaths compared to chemotherapy alone. As a result, the drug was voluntarily pulled off the market in June 2010.

This new approval is based on a new, lower dosing regimen, a different schedule in combination with chemotherapy or on its own, and a new patient population.

Related article: Faster Drug Approvals Mean Healthier Patients (Maybe)

“We are approving Mylotarg after a careful review of the new dosing regimen, which has shown that the benefits of this treatment outweigh the risk,” said Richard Pazdur, MD, in a statement. Pazdur is Director of the FDA’s Oncology Center of Excellence and Acting Director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research “Mylotarg’s history underscores the importance of examining alternative dosing, scheduling, and administration of therapies for patients with cancer, especially in those who may be most vulnerable to the side effects of treatment.”

In a trial examining the safety of Mylotarg with chemotherapy in adults, 271 patients with newly diagnosed CD33-positive AML received either Mylotarg in combination with daunorubicin and cytarabine or daunorubicin and cytarabine alone. Patients receiving Mylotarg in combination with chemotherapy achieved a median of 17.3 month of event-free survival compared to 9.5 months with chemotherapy alone.

For patients intolerant of chemotherapy or for those who choose to forgo it, Mylotarg was tested as a stand-alone treatment in 237 patients. Patients receiving Mylotarg had a median survival rate of 4.9 months compared with 3.6 months for those only receiving supportive care. In a second trial with 57 patients who had experienced one relapse, 26% achieved complete remission that lasted 11.6 months after treatment with Mylotarg.

Mylotarg includes a boxed warning for hepatoxicity and veno-occlusive disease or sinusoidal obstruction syndrome. It is contraindicated in patients hypersensitive to Mylotarg or any of its components. Read the full prescribing information here.