The targeted agent quizartinib showed promise in the treatment of a subset of patients with treatment-resistant acute myeloid leukemia (AML), according to the results of a study presented at the 54th Annual Meeting of the American Society of Hematology in Atlanta, Georgia.
Acute myeloid leukemia is a cancer of the bone marrow 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, with the average age at diagnosis being more than 65 years. Some patients with AML have a mutation in a gene called FLT3-ITD, which is sort of like a “power switch” that leukemia cells use to spread more aggressively—it helps the cancer cells grow back immediately after chemotherapy. Researchers have long been searching for a way to turn that “switch” off.
Quizartinib is an oral, liquid, targeted agent known as an FLT3 receptor tyrosine kinase inhibitor and is active against both ITD mutant and wild type FLT3. It is designed to “turn off” the FLT3-ITD mutation. Researchers conducted a phase II study to evaluate the safety and efficacy of quizartinib therapy in FLT3-ITD positive (+) and FLT3-ITD negative (-) patients.
The study included 333 patients in two cohorts. The majority of patients carried the mutation. The second cohort involved 137 patients—99 with the mutation and 38 without. The results indicated that patients with the mutation achieved a complete remission rate of 44%, a median duration of response of 11.3 weeks, and median overall survival of 23.1 weeks. Patients without the mutation had a 34% complete response rate.
The number of patients who were able to continue on to receive a stem cell transplant was significant—47 of the 137 were able to receive a transplant and 18 had survived 60 weeks after treatment with no disease recurrence.
The researchers noted that quizartinib was well tolerated and is the first single-agent drug to produce clinical benefit in this subset of patients who have failed previous therapy. They hope that these results and those of future phase III trials will lead to FDA-approval of quizartinib.
Cortes JE, Perl AE, Dobret H, et al. Final results of a phase 2 open-label, monotherapy efficacy and safety study of quizartinib (AC220) in patients ? 60 years of age with FLT3 ITD positive or negative relapsed/refractory acute myeloid leukemia. Blood (ASH Annual Meeting Abstracts) 2012; 120: Abstract 48.
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