The broad goal of the proposed research project is to improve treatment outcomes for patients with FLT3-mutant acute myeloid leukemia (AML). FLT3 mutations are detected in approximately 25-30% of AML patients. Recently, we have found that two drug-resistant FLT3 kinase domain mutations represent the most common cause of relapse in AML patients undergoing treatment with AC220 (quizartinib), the first clinically active investigational inhibitor of FLT3 for patients with AML. We have preliminary evidence that the most common AC220-resistant mutation in AML patients is sensitive in the laboratory to crenolanib, a drug that has already undergone clinical trial evaluation for other types of cancer. Crenolanib is also active in the laboratory against activation loop (AL) mutations in FLT3, which are found in 5-10% of AML patients. The second AC220-resistant mutation is sensitive to ponatinib, another investigational drug that is active in patients with chronic myeloid leukemia.
The specific aims of this proposal are to: 1) assess the activity of crenolanib against clinically-important FLT3 mutant isoforms in vitro and in vivo;2) assess the ability of crenolanib and ponatinib to collectively suppress all secondary FLT3-ITD kinase domain mutants in vitro and in vivo;and 3) determine the structural and functional impact of AL mutations in FLT3. This research focuses on AML, which impacts approximately 13,000 Americans annually, the majority of whom die of their disease within 1-2 years. It is anticipated that the proposed research will: 1) determine the potential of a novel FLT3 inhibitor as a treatment for AML associated with activation loop mutations in FLT3;2) inform the development of a possible combination FLT3 inhibitor clinical trial;3) provide insights into the structural and signaling impacts of activation loop mutations. The research design includes in vitro and in vivo as well as structural and signaling studies, and in addition, translational studies of primary samples, including from AML patients who have developed resistance to AC220 treatment.

Public Health Relevance

This research project is relevant to the health needs of those in the USA and abroad. Specifically, it attempts to address the most common mechanisms of loss of response to the most effective targeted cancer therapeutic developed for the treatment of acute myeloid leukemia in the recent past. If successful, the proposed studies may lead to combination treatment approaches that could substantially improve outcomes in acute myeloid leukemia patients, and could benefit the lives of tens of thousands of individuals diagnosed with this condition annually throughout the world.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Basic Mechanisms of Cancer Therapeutics Study Section (BMCT)
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Arya, Suresh
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University of California San Francisco
Internal Medicine/Medicine
Schools of Medicine
San Francisco
United States
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Smith, Catherine C; Paguirigan, Amy; Jeschke, Grace R et al. (2017) Heterogeneous resistance to quizartinib in acute myeloid leukemia revealed by single-cell analysis. Blood 130:48-58
Smith, Catherine Choy; Lasater, Elisabeth A; Lin, Kimberly C et al. (2014) Crenolanib is a selective type I pan-FLT3 inhibitor. Proc Natl Acad Sci U S A 111:5319-24