Comprehensive comparison and biologic activity of novel therapeutic agents in NPM1 mutated Acute Myeloid Leukemia (AML)

Acute Myeloid Leukemia (AML) is frequently associated with mutations of NPM1 (NPM1c+) and even if considered to be of better prognosis for younger patients, relapse is frequent and outcome remains poor for elder patients with a need for novel treatment strategies. Differentiation-based therapy by all trans retinoic acid (ATRA) combined with arsenic trioxide (ATO) induce proteasomal degradation of NPM1c protein, NPM1 nuclear re localization, differentiation and apoptosis in NPM1c+ cells and blast clearance in relapsed/refractory AML patients. In line, the XPO1 inhibitor Selinexor showed similar results in vitro associated with down regulation of a specific HOX gene signature. BET inhibitors (BETi) OTX015 (MK-8628) and JQ1 yield antileukemic activity and here we demonstrate their effects in NPM1c+ leukemia cells compared to ATO+ATRA and Selinexor. Compared to ATO+ATRA and Selinexor, BRDi induced TP53 independent apoptosis, differentiation, proteasomal NPM1c degradation and nuclear relocalization in NPM1c+ OCI-AML3 cell line and to different extend in patient derived blast cells. As ATO+ATRA and Selinexor had significant biological activity in NPM1c+ cell line IMS-M2, these cells were resistant to BETi exposure, except for nuclear re localization of NPM1 which is a general phenomenon upon treatment with all three drug types. Gene profiling revealed that BRDi downregulate a BRD specific core gene signature in OCI-AML3 and IMS-M2 cells but IMS-M2 cells yield a transcriptional resistance signature including upregulation of the Wnt/beta-catenin pathway. HOX gene clusters in OCI-AML3 cells and IMS-M2 cells are heterogeneously regulated by BETi and are down regulated by ATO+ATRA in line with results reported for Selinexor treatment. Taken together, our preclinical results encourage clinical testing of ATO+ATRA, Selinexor and BRDi in NPM1c+ AML patients.

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