Researchers from the University of Pittsburgh have reported that single-agent Mylotarg® (gemtuzumab ozogamicin) resulted in a complete remission (CR) rate of 30% in patients 70 years or older with newly diagnosed acute myeloid leukemia (AML). The details of this study were recently published in the journal Cancer.1
Acute myeloid leukemia is a cancer of the bone marrow (spongy portion found in the middle of bones) and blood characterized by the rapid, uncontrolled growth of immature white blood cells known as myelocytes. The disease is more common in adults than in children; average age at diagnosis is more than 65 years.
There have been relatively large improvements in survival of younger patients with AML over the past two decades due to increased dose-intensity of therapy; this includes stem cell transplants. However, there has been little, if any, improvement in the treatment of elderly patients with AML, often because elderly patients are not able to tolerate the more aggressive treatments used for younger patients. Treatment of elderly patients with AML remains unsatisfactory, and most patients die within a few months of diagnosis. One of the reasons for the dismal prognosis is the association with adverse cytogenetic and molecular abnormalities.
Mylotarg is comprised of two separate components, a monoclonal antibody and a toxin from the bacteria Micromonospora echinospora. The monoclonal antibody portion of Mylotarg binds to a receptor called the CD 33 receptor, which is found on myeloid cells. The CD33 receptor is present in 80-90% of AML cells but is not present on the normal hematopoietic stem cell. Thus, Mylotarg can selectively kill leukemia cells. Mylotarg was approved by the U.S. Food and Drug Administration in 2000 for the treatment of patients with AML over the age of 60 who have failed initial treatment.
The current study involved 49 patients with newly diagnosed AML 70 years of age or older. All were ineligible or unsuitable for treatment with standard intensive combination chemotherapy. Patients on this study received single-agent Mylotarg.
- The CR rate was 14% for all treated patients.
- The CR rate was 30% for patients with intermediate-risk cytogenetics.
- The CR rate was 0% for patients with adverse cytogenetics.
- Median survival was 3.7 months for all patients.
- Median survival for patients achieving a CR was 11.8 months.
These researchers concluded that single-agent Mylotarg is a treatment option for older patients with intermediate-risk AML.