Inhibition of Bcl-2 Synergistically Enhances the Antileukemic Activity of Midostaurin and Gilteritinib in Preclinical Models of FLT3-Mutated Acute Myeloid Leukemia

Abstract

Purpose: To investigate the efficacy of the combination of the FLT3 inhibitors midostaurin or gilteritinib with the Bcl-2 inhibitor venetoclax in FLT3-ITD acute myeloid leukemia (AML) and the underlying molecular mechanism. Experimental Design: Using both FLT3-ITD cell lines and primary patient samples, annexin V-FITC/propidium iodide staining and flow cytometry analysis were used to quantify cell death induced by midostaurin or gilteritinib, alone or in combination with venetoclax. Western blot analysis was performed to assess changes in protein expression levels of members of the JAK/ STAT, MAPK/ERK, and PI3K/AKT pathways, and members of the Bcl-2 family of proteins. The MV4-11-derived xenograft mouse model was used to assess in vivo efficacy of the combination of gilteritinib and venetoclax. Lentiviral overexpression of Mcl-1 was used to confirm its role in cell

Synergistic effect of BCL2 and FLT3 co-inhibition in acute myeloid leukemia

“…Using multiple, orthogonal approaches, we validated the synergistic relationship between the effects of BCL2 and FLT3 inhibition that was predicted by our previous work [11] and expanded preclinical work by Ma et al [12] using genetic validation and clinical-grade inhibitors that could be more readily translated to the clinic as combination strategies. We showed that depletion of BCL2 via both gene silencing and chemical inhibition in addition to FLT3 inhibition increased cell death in FLT3-ITD cell lines and primary AML patient samples beyond that of each perturbation alone, an effect which was not observed to the same extent in the case of FLT3-WT.…”

“…1 a), prompting further validation study of the combination of FLT3 and BCL2 inhibitors. Previous work by Ma et al [ 12 ] also showed the in vitro effects of combining FLT3 and BCL2 inhibitors. This work stemmed from the observation that FLT3 inhibitors result in downmodulation of the expression of myeloid cell leukemia 1 (MCL1), a known mechanism of resistance to BCL2 inhibitors, and could improve activity of BCL2 inhibitors.…”

“…These proteins bind BCL2-associated X protein (BAX) and BCL2 antagonist/killer (BAK), sequestering them to prevent apoptosis induction. Ma et al demonstrate that FLT3 inhibitors downregulate MCL1, causing AML cells to rely more on the binding of BAX and BAK to BCL2 [12]. Therefore, when venetoclax is added to a FLT3 inhibitor, they suggest there is synergy because both MCL1 and BCL2 expressions are reduced, increasing the dampening of the pro-survival activity of the AML blasts.…”

Targeting Bcl-2 Proteins in Acute Myeloid Leukemia

“…Here, we introduce several combinations that can reduce the MCL-1 level indirectly to circumvent the resistance. Indirect MCL-1 inhibitors include the following compounds: bromodomain extra-terminal protein inhibitors (BETis), which reduce MCL-1 and BCL-XL levels while increasing BIM levels and enhance the lethal effects of venetoclax on AML ( 97 ); cyclin-dependent kinase 9 (CDK9) inhibitors, which inhibit the transcription of MCL-1 ( 98 ); midostaurin or gilteritinib, FLT3 inhibitors that induce downregulation of MCL-1 to increase venetoclax activity ( 99 ); CUDC-907, a dual PI3K and histone deacetylase inhibitor that downregulates MCL-1, upregulates BIM, and induces DNA damage ( 100 ); MEK inhibitors ( 101 ); MDM2 inhibitors ( 102 ); PI3K inhibitors ( 103 ); and selinexor, an XPO1-selective inhibitor ( 104 ). In addition, an inhibitor of the Nedd8-activating enzyme (MLN4924) can upregulate Noxa, and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) inhibitors (statins) can upregulate PUMA.…”

Cotargeting of XPO1 Enhances the Antileukemic Activity of Midostaurin and Gilteritinib in Acute Myeloid Leukemia

“…Furthermore, we examined genes coding for known interacting partners of XPO1 from literature [ 15 , 16 , 17 , 18 ] and the comprehensive database NESdb [ 19 ] and found that the effect of the knockout of many of these genes was also predicted to be synergistic with midostaurin ( Figure 1 e; Table 1 ); the depletion was especially strong for Karyopherin-β1 (KPNB1) and Baculoviral IAP Repeat Containing 5 (BIRC5). BCL2 inhibition with venetoclax has been already shown to sensitize FLT3 -mutated AML cell lines to gilteritinib [ 20 ]. A Phase 1b study of venetoclax and gilteritinib in patients with Relapsed/Refractory AML also demonstrated efficacy, with 50% of FLT3-mutant patients achieving composite complete remission and an additional 40% reaching a morphologic leukemia-free state [ 21 ].…”