Author ORCID Identifier


Date of Graduation


Document Type

Thesis (MS)

Program Affiliation

Biochemistry and Molecular Biology

Degree Name

Masters of Science (MS)

Advisor/Committee Chair

Marina Konopleva, MD, PhD

Committee Member

Michael Andreeff, MD, PhD

Committee Member

Joya Chandra, PhD

Committee Member

Rong Chen, PhD

Committee Member

Pierre McCrea, PhD


The MCL-1 inhibitor S63845 synergizes with the FLT3 inhibitor midostaurin for potent anti-leukemic effect in preclinical human models of FLT3-ITD mutated acute myeloid leukemia (AML). Acute Myeloid leukemia (AML) is a neoplastic blood disorder defined by a characteristically rapid growth rate and altered behavior of myeloid cells in the bone marrow. The FLT3 receptor is responsible for the upstream regulation of many key processes in hematopoietic cells. FLT3 internal tandem duplication (ITD) mutations are common in leukemia and have been observed in up to a third of newly diagnosed AML patients. FLT3-ITD have been implicated as a driver mutation partly responsible for disease progression and associated with increased risk of relapse and lower probability of survival. This leads to the constitutive activation of the FLT3-ITD receptor and consequently the activation of downstream constituents central to regulating cellular functions. The ultimate outcome of FLT3-ITD mutations in AML is the loss of homeostasis in hematopoietic cells and progression of the leukemic disease state. Inhibitors of the FLT3 receptor inhibit activation and subsequent downstream phosphorylation in pathway which promote AML survival and progression. The FLT3 inhibitor midostaurin acts upon possessing the FLT3 receptor and displays therapeutic efficacy against the constituently active FLT3-ITD receptor. The addition of midostaurin is a significant advance in leukemic armamentarium, but there are still challenges for the treatment of FLT3-mutated AML through the development of therapy resistance. Among mechanisms of resistance to TKI that arise from non-FLT3 dependent pathways, most notable are the resistance mechanisms relating to the cell's systems which govern the apoptotic process. This has led to interest in the pro-survival BCL-2 family member MCL-1 due to the observation across cancers of therapy resistance and relapse associated with its amplification. Of relevance to our project is the selective MCL-1 inhibitor S63845. In preclinical studies, S63845 was found to exhibit dose-dependent anti-tumor activity in-vitro and was found to be well tolerated by mice in the in-vivo studies. Here we studied the pre-clinical efficacy of S63845 and midostaurin in AML cell lines expressing FLT3-WT or mutant FLT3-ITD receptor. S63845 in combination with midostaurin synergistically promoted anti-leukemic effect in-vitro. Midostaurin lead to the reduction of MCL-1 and sensitized cells to MCL-1 inhibition. Mechanistically, midostaurin lead to changes in MCL-1 phosphorylation and promotion of its proteasomal degradation. In addition, because resistance to the BCL-2 inhibitor venetoclax is characterized diminished by upregulation of MCL-1 we also studied the impact of the combination of venetoclax resistant FLT3-ITD AML cells. Overall, our results indicate sensitivity towards the combination of midostaurin and S63845 in venetoclax resistant AML cells. This supports the use of the combination of S63845 and midostaurin as a second line treatment in the event of treatment failure or relapse post-venetoclax therapy in FLT3- ITD AML.


Leukemia, FLT-3, MCL-1, Apoptosis, Therapy Resistance, TKI, midostaurin, s63845, gilteritinib, venetoclax



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