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Cancer Discov. 2019 Aug;9(8):1050-1063. doi: 10.1158/2159-8290.CD-18-1453. Epub 2019 May 14.

Clonal Selection with RAS Pathway Activation Mediates Secondary Clinical Resistance to Selective FLT3 Inhibition in Acute Myeloid Leukemia.

Author information

1
Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, Pennsylvania.
2
Division of Hematology and Oncology, University of California, San Francisco, San Francisco, California.
3
Hematology Division, Chaim Sheba Medical Center, Tel Aviv University, Tel-Hashomer, Israel.
4
Roswell Park Comprehensive Cancer Center, Buffalo, New York.
5
Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
6
Mission Bio, San Francisco, California.
7
Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California.
8
Department of Translational Oncology, Genentech, Inc., San Francisco, California.
9
Philadelphia Veterans Hospital, Philadelphia, Pennsylvania.
10
Division of Hematology-Oncology, University of Pennsylvania, Philadelphia, Pennsylvania. Alexander.perl@uphs.upenn.edu.
#
Contributed equally

Abstract

Gilteritinib is a potent and selective FLT3 kinase inhibitor with single-agent clinical efficacy in relapsed/refractory FLT3-mutated acute myeloid leukemia (AML). In this context, however, gilteritinib is not curative, and response duration is limited by the development of secondary resistance. To evaluate resistance mechanisms, we analyzed baseline and progression samples from patients treated on clinical trials of gilteritinib. Targeted next-generation sequencing at the time of AML progression on gilteritinib identified treatment-emergent mutations that activate RAS/MAPK pathway signaling, most commonly in NRAS or KRAS. Less frequently, secondary FLT3-F691L gatekeeper mutations or BCR-ABL1 fusions were identified at progression. Single-cell targeted DNA sequencing revealed diverse patterns of clonal selection and evolution in response to FLT3 inhibition, including the emergence of RAS mutations in FLT3-mutated subclones, the expansion of alternative wild-type FLT3 subclones, or both patterns simultaneously. These data illustrate dynamic and complex changes in clonal architecture underlying response and resistance to mutation-selective tyrosine kinase inhibitor therapy in AML. SIGNIFICANCE: Comprehensive serial genotyping of AML specimens from patients treated with the selective FLT3 inhibitor gilteritinib demonstrates that complex, heterogeneous patterns of clonal selection and evolution mediate clinical resistance to tyrosine kinase inhibition in FLT3-mutated AML. Our data support the development of combinatorial targeted therapeutic approaches for advanced AML.See related commentary by Wei and Roberts, p. 998.This article is highlighted in the In This Issue feature, p. 983.

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