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Phase III study shows quizartinib prolongs overall survival for patients with deadly type of relapsed or refractory AML

A study led by The University of Texas MD Anderson Cancer Center revealed that the investigational drug quizartinib prolonged overall survival for patients with a deadly form of acute myeloid leukemia (AML) linked to a genetic mutation called FMSlike internal tandem duplications (FLT3- ITD).

“Currently, there are no approved targeted therapies for patients with relapsed FLT3- ITD-associated AML, which represent a significant unmet medical need,” said Cortes, deputy chair and professor of Leukemia and lead investigator of the study called QUANTUM-R. “Our findings demonstrated that patients on quizartinib alone had an estimated overall survival of 27 percent after 52 weeks of treatment compared to20 percent for patients on standard chemotherapies.”

The study confirmed the efficacy and safety of quizartinib and the value of targeting FLT3-ITD with this novel agent. It is the first trial to demonstrate improved overall survival for FLT3-ITD-associated AML patients who were treatment-resistant or who relapsed after prior therapy. The study followed 367 patients for 103 weeks at which time the first analyses were conducted. Minimal side effects were observed.

Cortes led the multi-institutional effort to develop and test quizartinib, a small molecule receptor tyrosine kinase inhibitor (TKI) targeting ITD abnormalities within the FLT3 gene. FLT3, a receptor tyrosine kinase commonly expressed in AML, is mutated in approximately one-third of AML patients. Tyrosine kinases are enzymes often linked to cancer as they play a critical role in cellular processes including cell growth, division, differentiation and cell death.

Patients enrolled in QUANTUM-R were 18 years or older who had refractory AML or who had relapsed six months or less following complete remission after receiving standard AML therapies. The study allowed participation regardless of whether the patient had received stem cell transplantation. Patients were randomized to be administered once-daily treatments with quizartinib, or to receive one of several chemotherapy options typically used after standard treatments have failed. Chemotherapies allowed were lowdose cytarabine, the combination of mitoxantrone, etoposide, and cytarabine, or the combination of fludarabine, cytarabine, and idarubicin.

The two study arms were similar in patient makeup with a median age of 55 years for patients receiving quizartinib, and 57 years for those receiving chemotherapy. Of the quizartinib group, 33 percent of patients were refractory, and 67 percent had relapses after an initial complete remission of six months or less prior to the study. Thirty-four percent of patients in the chemotherapy group were refractory and 66 percent had relapsed after pre-study complete remission of six months or less.

“These pivotal data confirm that targeting FLT3-IT with this potent new therapy may be of significant clinical value,” said Cortes. “These results represent the first positive Phase III trial to demonstrate improved overall survival in patients with AMLassociated FLT3-ITD.”