Abstract 4958: VTP50469 is a novel, orally available menin-MLL1 inhibitor effective againstMLL-rearranged and NPM1-mutant leukemia

Inhibition of the menin(MEN) and MLL1(KMT2A) interaction reverses leukemic gene expression driven by MLL-fusion proteins and is a potential targeted therapeutic strategy in MLL-rearranged AML. Recent data show that inhibition of this interaction could also be efficacious in NPM1-mutant AML. We developed potent and selective menin-MLL1 inhibitors that are highly selective and effective in vitro and in vivo. Structure-based design yielded a potent small-molecule inhibitor of the menin-MLL1 binding interaction, VTP-49477 (K i =12+5 pM). Human and mouse leukemia cell lines driven by MLL-fusion proteins or NPM1 mutations were selectively sensitive to VTP-49477 (IC 50 of ~10 nM). Optimization of the inhibitor structure led to an orally available inhibitor, VTP-50469 (K i =104+30 pM). Similar to VTP-49477, human cell lines and mouse primary cells carrying MLL-fusions or NPM1c-mutations were highly sensitive to treatment with VTP-50469 (IC 50 ~20 nM). Mechanistically, treatment of NPM1-mutant OCI-AML3 cells and MLL-AF9 rearranged MOLM13 cells with VTP-50469 caused u003e20-fold reduction of menin in high-molecular-weight protein complexes as assessed by glycerol gradient sedimentation. Concordantly, VTP-50469 treatment resulted in u003e10-fold reduction in menin chromatin occupancy as assessed by ChIP-seq in MLL-AF4 rearranged RS4;11 and MOLM13 cells. Furthermore, treatment with either VTP50469 or VTP4777 reduced expression of common MLL-fusion target genes in RS4;11 and MOLM13 cells and also modulated gene expression in NPM1-mutant leukemia cells. Human PDX models were treated with either VTP-49477 or VTP-50469. Treatment of MLL-rearranged B-ALL and AML PDXs (n=3) with VTP-49477 for 28 days (50mg/kg, bid, IP) resulted in significant reduction of leukemia burden (median: 2-fold in BM, 3-fold in SP, and 6-fold in PB). For oral dosing, VTP-50469 was formulated in mouse chow (0.1%, total daily dose ~175mg/kg/day) and PDX models were treated with this chow for 28 days. Mice engrafted with MLL-rearranged B-ALL, MLL-rearranged AML and NPM1-mutant AML PDXs (n=5) showed dramatic reductions of human leukemia cells in peripheral blood, spleen and bone marrow as compared to control treated mice (median: 225-fold in BM, 14-fold in SP and 129-fold in PB). AML cells showed increased differentiation with elevated expression of CD11b, CD13, CD86 and loss of common MLL-fusion target gene expression. Treatment of MLL1 wt and NPM1 wt B-ALL and AML PDXs with VTP-50469 did not reduce leukemia burden, confirming VTP-50469 menin-MLL1 target selectivity. Treatment with VTP-50469 did not alter normal peripheral blood counts and no weight loss was observed during treatment. Therefore, at a highly effective dose, VTP-50469 does not have detectable toxicity. Based on these data, inhibition of the menin-MLL1 interaction with VTP-50469 may have beneficial activity in up to 40% of human AML and most infant leukemias. Citation Format: Andrei V. Krivtsov, Benjamin K. Eschle, Matthew Witkin, Jayant Y. Gadrey, Hannah J. Uckelmann, Sayuri Kitajima, Gerard M. McGeehan, Scott A. Armstrong. VTP50469 is a novel, orally available menin-MLL1 inhibitor effective against MLL -rearranged and NPM1-mutant leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4958.