The study participants were treated with cytarabine and daunorubicin, standard chemotherapy agents, and Mylotarg (gemtuzumab ozogamicin), an anti-body targeted chemotherapy. Interim results show that 83 percent of the evaluable participants (15 of 18) treated with the combination therapy achieved complete remission, and that the therapy was well tolerated. The median duration of complete response has not yet been reached (median follow-up is 193 days).
"Acute myeloid leukemia is an aggressive disease that requires aggressive treatment," says the study's principal investigator, Daniel DeAngelo, MD, PhD, of Dana-Farber. "It's very early in our investigation of this combination of therapies, but essentially it gave us a higher rate of remission than we've seen before without an increase in the side effects that typically accompany these conventional therapies. More research is needed, but these preliminary Phase II results show that we are on the right track."
Antibody-targeted chemotherapy with Mylotarg, delivers the toxin to cells that express the CD33 protein on their surface, meaning that it attacks primarily diseased cells and generally does not affect healthy cells. Previous research has shown that when used alone, Mylotarg has been associated with delayed or incomplete platelet recovery and, in some cases, a liver condition called hepatic veno-occlusive disease. Standard chemotherapy, while effective, is associated with severe side effects, such as mucositis that causes sores in the mouth, throat and digestive tract, diarrhea, vomiting, and hair loss.
"We've found that standard chemotherapy boosted the efficacy of Mylotarg, resulting in a complete remission – including platelet recovery – without significantly increasing the side effects," says DeAngelo. "We need to see how these patients do over time, but right now the results are promising. It opens the door for more research to determine if this combination will allow more patients to benefit from antibody-targeted chemotherapy."
Currently, Mylotarg, which is manufactured by Wyeth Pharmaceuticals, is approved for the treatment of selected older patients with CD33-positive AML in first relapse.
Dana-Farber Cancer Institute (www.danafarber.org) is a principal teaching affiliate of the Harvard Medical School and is among the leading cancer research and care centers in the United States. It is a founding member of the Dana-Farber/Harvard Cancer Center (DF/HCC), designated a comprehensive cancer center by the National Cancer Institute.