Contributions
Abstract: EP379
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
Nucleophosmin (NPM1) is the most commonly mutated gene in adult AML (approximately 30%), which results in its aberrant cytoplasmic localization (NPM1c). The interaction of mixed-lineage leukemia (MLL1) with menin in NPM1 mutated AML shares a common HOX gene signature and dependencies as that of MLL-rearrangements (MLL1-r) with menin. Indeed, inhibition of menin has demonstrated anti-leukemia activity in both NPM1c and MLL-r AML. NPM1 mutations in AML frequently occur in patients with other mutations, such as FLT3-ITD and FLT3 tyrosine kinase domain (TKD) mutations. Co-inhibition of menin and FLT3 has demonstrated enhanced anti-leukemia activity in MLL-r/FLT3- and NPM1c/FLT3-mutated AML.
Targeting Bcl-2, a critical factor for AML cell and AML stem/progenitor cell survival, has emerged as a promising therapeutic option for patients with AML. However, despite the major improvement of combining the Bcl-2 inhibitor venetoclax with hypomethylating agents, most patients develop resistance and ultimately relapse.
Aims
To investigate the anti-leukemic activity and potential synergism and mechanisms of the combination of the menin-MLL1 inhibitor SDNX-50469, an equipotent surrogate of the clinical compound SNDX-5613 and venetoclax in vivo in an NPM1c/FLT3-ITD/TKD patient-derived xenograft (PDX) model.
Methods
The PDX cell engrafted NSG mice were treated with 0.05 or 0.1% SNDX-50469-spiked chow, venetoclax (50 mg/kg), or 0.1% SNDX-50469 plus venetoclax for one month. Engraftment and disease progression were assessed by flow cytometric measurement of human CD45+ cells in mouse peripheral blood. Survival was monitored. The treatment effects on various leukemia cell populations and their protein expression levels were determined by CyTOF mass cytometry.
Results
Menin inhibition exhibited strong anti-leukemia activity and significantly prolonged mouse survival, which was further enhanced when combined with venetoclax, while venetoclax alone had minimal effect. The combination was most effective in extending mouse survival (143 d for 0.1% SNDX-50469 plus venetoclax, P = 0.0003; 131 d and 125 d for 0.1% or 0.05% SNDX-50469, respectively, P = 0.0001 for both; 69 d for venetoclax, P = 0.025; vs. 61 d for controls). At the end of treatments, bone marrow cells were collected and CyTOF analysis demonstrated that menin inhibition preferentially targeted CD34+CD38+ cells, while venetoclax targeted CD34+CD38- cells. Only the combined inhibition of menin and Bcl-2 effectively eliminated bulk and CD34+CD38+/CD34+CD38- stem/progenitor cells. Menin inhibition also increased the CD11b+ myeloid cell population. Mechanistically, menin inhibition decreased multiple anti-apoptotic Bcl-2 proteins including Bcl-2 and Bcl-xL, and concomitantly increased pro-apoptotic Bcl-2 proteins such as Bax that seemingly enhanced the activity of Bcl-2 inhibition by venetoclax. However, we observed increases of p-FLT3 in the surviving leukemia cells at the end of the treatments, particularly in the combination treated group, which may contribute to the regrowth of leukemia cells.
Conclusion
Our study further validated menin as a therapeutic target and demonstrated that its inhibition synergizes with venetoclax in NPM1/FLT3-mutated AML, which warrants further clinical evaluation. Inhibition of FLT3 may further enhance the therapeutic efficacy of menin and Bcl-2 co-targeting in NPM1 and FLT3 mutated AML.
Keyword(s): AML, BCL2, Leukemic stem cell, MLL
Abstract: EP379
Type: E-Poster Presentation
Session title: Acute myeloid leukemia - Biology & Translational Research
Background
Nucleophosmin (NPM1) is the most commonly mutated gene in adult AML (approximately 30%), which results in its aberrant cytoplasmic localization (NPM1c). The interaction of mixed-lineage leukemia (MLL1) with menin in NPM1 mutated AML shares a common HOX gene signature and dependencies as that of MLL-rearrangements (MLL1-r) with menin. Indeed, inhibition of menin has demonstrated anti-leukemia activity in both NPM1c and MLL-r AML. NPM1 mutations in AML frequently occur in patients with other mutations, such as FLT3-ITD and FLT3 tyrosine kinase domain (TKD) mutations. Co-inhibition of menin and FLT3 has demonstrated enhanced anti-leukemia activity in MLL-r/FLT3- and NPM1c/FLT3-mutated AML.
Targeting Bcl-2, a critical factor for AML cell and AML stem/progenitor cell survival, has emerged as a promising therapeutic option for patients with AML. However, despite the major improvement of combining the Bcl-2 inhibitor venetoclax with hypomethylating agents, most patients develop resistance and ultimately relapse.
Aims
To investigate the anti-leukemic activity and potential synergism and mechanisms of the combination of the menin-MLL1 inhibitor SDNX-50469, an equipotent surrogate of the clinical compound SNDX-5613 and venetoclax in vivo in an NPM1c/FLT3-ITD/TKD patient-derived xenograft (PDX) model.
Methods
The PDX cell engrafted NSG mice were treated with 0.05 or 0.1% SNDX-50469-spiked chow, venetoclax (50 mg/kg), or 0.1% SNDX-50469 plus venetoclax for one month. Engraftment and disease progression were assessed by flow cytometric measurement of human CD45+ cells in mouse peripheral blood. Survival was monitored. The treatment effects on various leukemia cell populations and their protein expression levels were determined by CyTOF mass cytometry.
Results
Menin inhibition exhibited strong anti-leukemia activity and significantly prolonged mouse survival, which was further enhanced when combined with venetoclax, while venetoclax alone had minimal effect. The combination was most effective in extending mouse survival (143 d for 0.1% SNDX-50469 plus venetoclax, P = 0.0003; 131 d and 125 d for 0.1% or 0.05% SNDX-50469, respectively, P = 0.0001 for both; 69 d for venetoclax, P = 0.025; vs. 61 d for controls). At the end of treatments, bone marrow cells were collected and CyTOF analysis demonstrated that menin inhibition preferentially targeted CD34+CD38+ cells, while venetoclax targeted CD34+CD38- cells. Only the combined inhibition of menin and Bcl-2 effectively eliminated bulk and CD34+CD38+/CD34+CD38- stem/progenitor cells. Menin inhibition also increased the CD11b+ myeloid cell population. Mechanistically, menin inhibition decreased multiple anti-apoptotic Bcl-2 proteins including Bcl-2 and Bcl-xL, and concomitantly increased pro-apoptotic Bcl-2 proteins such as Bax that seemingly enhanced the activity of Bcl-2 inhibition by venetoclax. However, we observed increases of p-FLT3 in the surviving leukemia cells at the end of the treatments, particularly in the combination treated group, which may contribute to the regrowth of leukemia cells.
Conclusion
Our study further validated menin as a therapeutic target and demonstrated that its inhibition synergizes with venetoclax in NPM1/FLT3-mutated AML, which warrants further clinical evaluation. Inhibition of FLT3 may further enhance the therapeutic efficacy of menin and Bcl-2 co-targeting in NPM1 and FLT3 mutated AML.
Keyword(s): AML, BCL2, Leukemic stem cell, MLL