A third of adult leukemia patients given the novel drug quizartinib (AC220) during a phase II study have achieved a composite response of either complete remission, or remission with incomplete platelet recovery or incomplete hematologic recovery, report US researchers.
The participants had either experienced relapse of their acute myeloid leukemia (AML) and were resistant to treatment with second-line salvage chemotherapy, or had relapsed after treatment with hematopoietic stem cell transplantation (HSCT), explains the team.
Furthermore, the safety findings in the cohort were manageable, write Mark Levis (Johns Hopkins University, Baltimore, USA) and colleagues in the abstract they presented at the 2012 American Society of Hematology Annual Meeting and Exposition in Atlanta, Georgia.
The most common adverse event was nausea, experienced by 38% of participants, followed by anemia, at 29%, and vomiting, at 26%.
"We can put two-thirds to three-quarters of adults with AML into remission with chemotherapy, but there's a 50 percent chance of the disease coming back, which usually ends up being fatal," said Levis in a press statement.
"Many patients in this trial were able to go on to receive a potentially life-saving bone marrow transplant. It caught us by surprise how well it [AC220] works," he added.
The cohort included 137 AML patients, of whom 99 (72%) were positive for FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD+) - which are known to be associated with early relapse of the disease after chemotherapy and a poor survival - and 38 (28%) who were negative for the duplications (FLT3-ITD-).
FLT3-ITD+ patients were aged a median 50 years and 50% were male, while the FLT3-ITD- patients were aged a median 55 years and 61% were male.
Female participants received a starting AC220 dose of 90 mg/day, while men received 135 mg/day initially and both took the drug continuously in 28-day cycles.
The researchers report composite complete remission rates of 44% for FLT3-ITD+ patients and 34% for FLT3-ITD- patients. Rates of complete remission, complete remission with incomplete platelet recovery, and complete remission with incomplete hematologic recovery were 4%, 0, and 40% for the FLT3-ITD+ group, and 3%, 3%, and 29% in the FLT3-ITD- group, respectively.
Median overall survival rates were 23.1 weeks and 25.6 weeks in FLT3-ITD+ and FLT3-ITD- patients, respectively.
In all, 14 (10%) patients experienced a treatment-related adverse effect that required them to cease taking the study drug, note the researchers.
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