The U.S. Food and Drug Administration has approved Pfizer’s Mylotarg (gemtuzumab ozogamicin) for adults and children with acute myeloid leukemia (AML) whose cancer carries the CD33 marker.
In adults, Mylotarg is approved as a first-line treatment in newly diagnosed patients. Children ages 2 and older can also be treated with the drug if their disease relapses or does not respond to initial treatment.
“The FDA approval of Mylotarg fills a critical unmet need for many adults and children with AML, which can be fatal in a matter of months or even weeks if not treated and has a high relapse rate,” Liz Barrett, global president of Pfizer Oncology, said in a press release.
“Based on clinical data, real-world experience and support from the AML community, we are grateful Mylotarg now has the potential to help a broad range of AML patients,” she added.
It was not the first time the FDA approved Mylotarg. In 2000, Mylotarg was granted accelerated approval to treat adults with CD33-positive AML who had a relapse. Patients also had to be older than 60 and not eligible for other chemotherapies.
But Pfizer’s confirmatory study failed to confirm the therapy’s benefits. The treatment also appeared to trigger toxic reactions, with early deaths among some patients. The data prompted the company to voluntarily withdraw the drug from the market.
The drug, however, remained on the market in Japan, and Pfizer also made it available to individual patients through its compassionate use programs. Given the lack of treatment options for AML patients, researchers and physicians did not give up on the drug’s potential.
Independent researchers started clinical trials, varying dosing amounts and schedules to explore whether the toxic effects could be reduced. These clinical trials, which Pfizer supported, formed the basis of the new FDA approval.
Among the studies was a placebo-controlled Phase 3 trial (NCT00927498) in newly diagnosed AML patients who received a lower Mylotarg dose in combination with chemotherapy. The study included 271 patients, of which 135 received active treatment.
Patients on Mylotarg lived without experiencing a relapse for 17.3 months. Those treated only with chemotherapy lived for 9.5 months.
Another study, called AML-19 (NCT00091234), treated elderly patients who would not tolerate other AML treatments, with either Mylotarg or best supportive care. Actively treated patients had a median overall survival of 4.9 months while those receiving best supportive care lived for 3.6 months.
A third study, MyloFrance-1, studied the drug in patients who had their first relapse. Among the 57 adult participants, 26 percent had a complete remission. They lived for a median of 11.6 months without relapsing further.
“Today is an important day for patients, their families and the entire AML community, as the approval of Mylotarg brings forth a long-awaited treatment option that may lead to deeper, more durable remissions for patients with AML,” said Jorge Cortes, MD, at the University of Texas MD Anderson Cancer Center.
The FDA sided with the researchers who believed Mylotarg remained a treatment option for AML in its approval of the drug.
“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,” 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, said in an agency press release.
“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,” he added.
But the approval does not mean that Mylotarg is now considered a risk-free treatment. Its prescription label still holds a boxed warning for liver toxicity, including severe and life-threatening hepatic veno-occlusive disease. The condition is characterized by blocked liver veins, and it has occurred in patients both treated with Mylotarg on its own and in combination with chemotherapy.
“After many years, we are finally seeing progress in the treatment of AML, which has renewed my hope in improving outcomes for my patients. I am pleased that I can now offer many adult and pediatric patients targeted treatment with Mylotarg,” Cortes said.
