Abstract 1293: HM43239, a novel FLT3 inhibitor in overcoming resistance for acute myeloid leukemia

Abstract

Introduction: Acute myeloid leukemia (AML) with FMS-like tyrosine kinase 3 (FLT3) mutation is associated with poor prognosis with a high risk of relapse after therapy and reduced overall survival. Currently, FLT3 inhibitors have shown clinical benefits in the corresponding AML patients. Activating mutations within internal tandem duplication (ITD) and tyrosine kinase domain (TKD) point mutations of FLT3 have been reported as oncogenic driver mutations in about 30% of AML. The acquired D835Y and F691L point mutations of FLT3-TKD are associated with resistance to FLT3-targeted AML therapy. In this study, we have characterized HM43239, a novel FLT3 inhibitor, and assessed its potential as a novel therapy in overcoming resistance for AML patients. Materials and Methods: In vitro site-directed competition binding assay was performed to measure interactions between HM43239 and FLT3 mutations. Standard proliferation assay, immunoblotting, and apoptosis analysis were carried out to validate the potency of HM43239 in AML resistance cell lines. In vivo study, HM43239 was evaluated in Ba/F3 cells expressing FLT3 ITD/F691L or FLT3 ITD/D835Y xenograft mice models. Combination studies were evaluated in Acute Myeloid Leukemia xenograft mice models. Results: HM43239 potently inhibited both FLT3 ITD/D835Y and FLT3 ITD/F691L mutations in preclinical evaluation. It showed high in vitro binding affinity to both mutations, and exhibited potent inhibitory activity in in vitro and in vivo models using Ba/F3 cells expressing FLT3 ITD/D835Y or FLT3 ITD/F691L. Moreover, HM43239 could overcome the FL-induced drug resistance with a higher cytotoxic potency in MOLM-14 cells harboring FLT3 ITD. In KG-1a cells, HM43239 potently inhibited phosphorylation of SYK, STAT3 and STAT5. In addition, it inhibited the proliferation and induced the apoptosis of leukemic stem cell (LSC) marker-expressing KG1a cells (CD34+/CD38- cells), suggesting the possibility of targeting LSC. Also, HM43239 significantly inhibited p-FLT3 and p-STAT5 under normal human plasma milieu in a dose-dependent manner in Ba/F3 and MOLM-14 cell line harboring FLT3 ITD. Furthermore, the combination treatment of HM43239 with various reagents (e.g., IAP inhibitor, chemotherapy, etc) demonstrated synergistic efficacy in mouse models, xenografted with both MV-4-11 and MOLM-13 cell lines without any significant toxicity. Conclusion: Taken together, HM43239 demonstrated the potential therapeutic efficacy for the treatment of AML patients, and implicated the mechanism of overcoming resistance and preventing relapse. Citation Format: JiSook Kim, InHwan Bae, JaeYul Choi, MinJeong Kim, JooYun Byun, MiJin Moon, EunYoung Lee, Yu-Yon Kim, Hyun Jeong Kang, Eunyoung Kim, SunYoung Jung, YoungGil Ahn, YoungHoon Kim, Kwee Hyun Suh. HM43239, a novel FLT3 inhibitor in overcoming resistance for acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1293.

NADPH oxidase mediated oxidative stress signaling in FLT3-ITD acute myeloid leukemia

“… Drug Description Function Ref. AMG 925 A potent, selective, and bioavailable FLT3/CDK4 dual kinase inhibitor Inhibits FLT3 mutants (e.g., D835Y) that are resistant to the current FLT3 inhibitors (e.g., AC220 and sorafenib) [ 84 ] Cabozantinib A multi-targeted TKI of FLT3, MET, AXL, VEGFR, and KIT Inhibits FLT3-ITD tyrosine kinase in a potent and sustained fashion [ 85 ] EC-70124 A hybrid indolocarbazole analog with a potent and selective inhibitory effect on FLT3 Potently inhibits wild-type and mutant FLT3, and also other important kinases such as PIM kinases [ 86 ] FN-1501 A potent inhibitor of FLT3 and other tyrosine kinases such as CDK4/6, KIT, PDGFR, ALK and RET tyrosine kinase proteins Antiproliferative activities against FLT3-ITD expressing cell line MV4-11 [ 87 ] HM43239 A active small molecule inhibitor of FLT3-ITD, FLT3-TKD, and FLT3- ITD/TKD double mutations Overcomes the FL-induced drug resistance with a higher cytotoxic potency in MOLM-14 cells harboring FLT3-ITD [ 88 ] MZH29 A type II FLT3 inhibitor that tolerated the F691L mutation Showed sustained inhibitory effects on wild-type and mutant FLT3, including the FLT3-ITD, FLT3-D835H/Y/V and FLT3-K663Q mutants [ 89 ] Pexidartinib A small molecule TKI with selective activity against the CSF1 receptor, KIT and FLT3-ITD Having inhibitory activity against the FLT3 TKI-resistant F691L gatekeeper mutation in relapsed/refractory FLT3-ITD-mutant AML [ 90 ] SEL24 A dual PIM and FLT3-ITD inhibitor Significant inhibitory activity on FLT3-ITD and tyrosine kinase domain (TKD) positive AML [ 91 ] SKLB-677 An FLT3 and Wnt/β-catenin signaling inhibitor Showed considerable suppression effects on leukemia stem-like cells in in vitro functional assays, but had no influence on normal HSCs [ 92 ] ALK anaplastic lymphoma kinase, CDK cyclin-dependent kinase, CSF1 colony-stimulating factor 1, KIT KIT proto-oncogene receptor tyrosine kinase, PDGFR platelet-derived growth...…”