FDA Approves Mylotarg (Gemtuzumab Ozogamicin) for Acute Myeloid Leukemia

The US Food and Drug Administration (FDA) has approved Mylotarg (gemtuzumab ozogamicin) for adults and children with certain types of acute myeloid leukemia (AML). Mylotarg was approved in 2000, but was taken off the market because of safety concerns. The new approval includes recommendations for a lower dose, a different treatment schedule, and a different patient population.

Mylotarg is now approved for adults newly diagnosed with AML whose tumors test positive for the antigen CD33. It’s also approved for children ages 2 and older with CD33-positive AML who have not gotten better with treatment, or whose cancer has come back after treatment.

“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, 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, in a statment. “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.”

AML is a type of leukemia that starts in bone marrow and can progress quickly. Mylotarg is a kind of targeted therapy called an antibody-drug conjugate. An antibody-drug conjugate is a monoclonal antibody linked to a chemotherapy drug. It is thought to work by blocking the connection between the cancer cells and the proteins that are helping them grow. Blocking the connection causes the cancer cells to die.

The FDA based its approval on 3 trials. In one trial, 271 people with newly diagnosed CD33-positive AML received either Mylotarg with standard chemotherapy, or chemotherapy alone. The trial measured event-free survival, which means how long people lived without life-threatening complications. Those who received Mylotarg with their chemo had an average event-free survival of 17.3 months compared with 9.5 months for those who only received chemotherapy.

The other 2 trials measured Mylotarg as a stand-alone treatment. One included 237 people with newly diagnosed AML who either chose not to or were not able to receive chemotherapy. Those who received Mylotarg lived an average 4.9 months compared with 3.6 months for those who did not. The other trial included 57 people with CD33-positive AML whose cancer had come back after treatment. After a course of Mylotarg, 26% of patients went into a complete remission for an average 11.6 months.

Side effects of Mylotarg include fever, nausea, infection, vomiting, bleeding, low blood counts, mouth sores, constipation, rash, headache, and elevated liver function tests. More severe side effects include liver damage, infusion-related reactions, and severe bleeding. The prescribing information includes a boxed warning that severe liver damage has occurred in some patients who took Mylotarg.

Women who are pregnant or breastfeeding should not take Mylotarg, because it may cause harm to a developing fetus or a newborn baby.

Mylotarg was granted orphan drug designation, which provides financial incentives to encourage the development of drugs for rare diseases.

Mylotarg is marketed by Pfizer, Inc.

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