A novel Menin-MLL1 inhibitor, DS-1594a, prevents the progression of acute leukemia with rearranged MLL1 or mutated NPM1

BACKGROUND

Mixed lineage leukemia 1-rearranged (MLL1-r) acute leukemia patients respond poorly to currently available treatments and there is a need to develop more effective therapies directly disrupting the Menin‒MLL1 complex. Small-molecule-mediated inhibition of the protein‒protein interaction between Menin and MLL1 fusion proteins is a potential therapeutic strategy for patients with MLL1-r or mutated-nucleophosmin 1 (NPM1c) acute leukemia. In this study, we preclinically evaluated the new compound DS-1594a and its salts.

METHODS

We evaluated the preclinical efficacy of DS-1594a as well as DS-1594a·HCl (the HCl salt of DS-1594a) and DS-1594a·succinate (the succinic acid salt of DS-1594a, DS-1594b) in vitro and in vivo using acute myeloid leukemia (AML)/acute lymphoblastic leukemia (ALL) models.

RESULTS

Our results showed that MLL1-r or NPM1c human leukemic cell lines were selectively and highly sensitive to DS-1594a·HCl, with 50% growth inhibition values < 30 nM. Compared with cytrabine, the standard chemotherapy drug as AML therapy, both DS-1594a·HCl and DS-1594a·succinate mediated the eradication of potential leukemia-initiating cells by enhancing differentiation and reducing serial colony-forming potential in MLL1-r AML cells in vitro. The results were confirmed by flow cytometry, RNA sequencing, RT‒qPCR and chromatin immunoprecipitation sequencing analyses. DS-1594a·HCl and DS-1594a·succinate exhibited significant antitumor efficacy and survival benefit in MOLM-13 cell and patient-derived xenograft models of MLL1-r or NPM1c acute leukemia in vivo.

CONCLUSION

We have generated a novel, potent, orally available small-molecule inhibitor of the Menin-MLL1 interaction, DS-1594a. Our results suggest that DS-1594a has medicinal properties distinct from those of cytarabine and that DS-1594a has the potential to be a new anticancer therapy and support oral dosing regimen for clinical studies (NCT04752163).

Abstract 1132: Development and characterization of a novel orally bioavailable menin-MLL inhibitor for treatment of acute leukemia patients with MLL-rearrangement or NPM1 mutation

DS-M1 is a novel, potent, orally bioavailable small molecule inhibitor of the binding of MLL1 fusion proteins and wild-type MLL1 to Menin in development for the treatment of patients with MLL1-rearranged (MLL1-r) or NPM1-mutated (NPM1-mu) acute leukemia. The interaction of MLL1 fusion proteins with menin plays an important role to enhance the proliferation and block the differentiation of hematopoietic cells, ultimately leading to acute leukemia. Furthermore, patients with MLL1-r acute leukemia respond poorly to currently available treatments, emphasizing the urgent need to develop more effective therapies directly disrupting the menin-MLL1 complex. Here we describe the characterization of DS-M1 and this study demonstrates the mechanism of action of DS-M1 as well as supports the oral dosing regimen planned for the initial clinical studies. DS-M1 selectively inhibited the cellular growth of MLL1-r or NPM1-mu human leukemic cell lines and primary cells from patients with GI50 of less than about 100 nM along with the cellular differentiation in vitro. RNA-seq and ChIP-seq analysis revealed that DS-M1 reduced the expression levels of MEIS1, PBX3 and HOXA9 genes in a concentration-dependent manner and dissociated the menin-MLL1 complex from the MEIS1 gene locus in MV-4-11, MOLM-13, and patient derived AML cells with MLL1-rearrangement. Interestingly, DS-M1 reduced the number of CD34+/CD38- leukemic stem cells (LSCs) in patient derived AML cells and induction of differentiation was also confirmed as measured by increased CD11b or CD14 expression. These results suggest that enhanced differentiation and loss of LSCs via the reduction of MEIS1, HOXA9, and PBX3 gene expression by DS-M1 is one of the main mechanisms of action for the antitumor activity of DS-M1. DS-M1 demonstrates significant survival benefit along with inhibition of MEIS1, HOXA9 and PBX3 expression in aggressive disseminated leukemia models intravenously inoculated with MV-4-11 and MOLM-13 cells as well as in patient-derived xenograft (PDX) models of MLL1-r or NPM1-mu acute leukemia. In disseminated MOLM-13 xenografts, treatment with 100 mg/kg qd of DS-M1 for 19 days produced durable response with event free survival &gt;100 days after last dose (5 out of 6 mice, increase in life span (ILS) &gt;515%). Furthermore, MLL1-r pediatric B-ALL-PDX mice treated with 50 mg/kg bid for 28 days and NPM1-mu AML-PDX mice treated with 100 mg/kg bid for 35 days were all survived (ILS &gt;254% and &gt;300%) without any detectable leukemic blast cells in bone marrow at 120 and 60 days after cessation of therapy, respectively. These data indicate that DS-M1 has a high potency as an antitumor drug with the potential to provide survival advantage in acute leukemia patients with MLL-r and NPM1-mu. Currently, a Phase 1/2 clinical study of DS-M1 is planned in AML and ALL patients with MLL-r or NPM1-mu.

Citation Format: Masashi Numata, Machiko Shiroishi, Kenji Yoshikawa, Noriyasu Haginoya, Tsuyoshi Hirata, Yoshimi Takata, Reina Nagase, Kohei Takashima, Akiko Kurimoto, Fumie Tanzawa, Yumiko Tomoe, Tomoaki Hamada, Ryutaro Kanada, Jun Watanabe, Yoshiko Kagoshima, Eri Tokumaru, Kenji Murata, Takayuki Baba, Taeko Shinozaki, Kazuyuki Hashimoto, Motohiro Kato, Shinji Tsutsumi, Mayumi Kitagawa, Kosaku Fujiwara, Yuki Abe. Development and characterization of a novel orally bioavailable menin-MLL inhibitor for treatment of acute leukemia patients with MLL-rearrangement or NPM1 mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1132.

Expression of mutant Asxl1 perturbs hematopoiesis and promotes susceptibility to leukemic transformation

Nagase and Inoue et al. generated a novel Asxl1 mutant mouse model to mimic clonal hematopoiesis and myelodysplastic syndromes caused by ASXL1 mutations and elucidated the effects of mutant versus wild-type ASXL1 on hematopoiesis, gene expression, and chromatin state.

Additional sex combs like 1 (ASXL1) is frequently mutated in myeloid malignancies and clonal hematopoiesis of indeterminate potential (CHIP). Although loss of ASXL1 promotes hematopoietic transformation, there is growing evidence that ASXL1 mutations might confer an alteration of function. In this study, we identify that physiological expression of a C-terminal truncated Asxl1 mutant in vivo using conditional knock-in (KI) results in myeloid skewing, age-dependent anemia, thrombocytosis, and morphological dysplasia. Although expression of mutant Asxl1 altered the functions of hematopoietic stem cells (HSCs), it maintained their survival in competitive transplantation assays and increased susceptibility to leukemic transformation by co-occurring RUNX1 mutation or viral insertional mutagenesis. KI mice displayed substantial reductions in H3K4me3 and H2AK119Ub without significant reductions in H3K27me3, distinct from the effects of Asxl1 loss. Chromatin immunoprecipitation followed by next-generation sequencing analysis demonstrated opposing effects of wild-type and mutant Asxl1 on H3K4me3. These findings reveal that ASXL1 mutations confer HSCs with an altered epigenome and increase susceptibility for leukemic transformation, presenting a novel model for CHIP.

A novel ASXL1-OGT axis plays roles in H3K4 methylation and tumor suppression in myeloid malignancies

ASXL1 plays key roles in epigenetic regulation of gene expression through methylation of histone H3K27, and disruption of ASXL1 drives myeloid malignancies, at least in part, via derepression of posterior HOXA loci. However, little is known about the identity of proteins that interact with ASXL1 and about the functions of ASXL1 in modulation of the active histone mark, such as H3K4 methylation. In this study, we demonstrate that ASXL1 is a part of a protein complex containing HCFC1 and OGT; OGT directly stabilizes ASXL1 by O-GlcNAcylation. Disruption of this novel axis inhibited myeloid differentiation and H3K4 methylation as well as H2B glycosylation and impaired transcription of genes involved in myeloid differentiation, splicing, and ribosomal functions; this has implications for myelodysplastic syndrome (MDS) pathogenesis, as each of these processes are perturbed in the disease. This axis is responsible for tumor suppression in the myeloid compartment, as reactivation of OGT induced myeloid differentiation and reduced leukemogenecity both in vivo and in vitro. Our data also suggest that MLL5, a known HCFC1/OGT-interacting protein, is responsible for gene activation by the ASXL1-OGT axis. These data shed light on the novel roles of the ASXL1-OGT axis in H3K4 methylation and activation of transcription.

High expression of ABCG2 induced by EZH2 disruption has pivotal roles in MDS pathogenesis

Both proto-oncogenic and tumor-suppressive functions have been reported for enhancer of zeste homolog 2 (EZH2). To investigate the effects of its inactivation, a mutant EZH2 lacking its catalytic domain was prepared (EZH2-dSET). In a mouse bone marrow transplant model, EZH2-dSET expression in bone marrow cells induced a myelodysplastic syndrome (MDS)-like disease in transplanted mice. Analysis of these mice identified Abcg2 as a direct target of EZH2. Intriguingly, Abcg2 expression alone induced the same disease in the transplanted mice, where stemness genes were enriched. Interestingly, ABCG2 expression is specifically high in MDS patients. The present results indicate that ABCG2 de-repression induced by EZH2 mutations have crucial roles in MDS pathogenesis.

Novel working hypothesis for pathogenesis of hematological malignancies: combination of mutations-induced cellular phenotypes determines the disease (cMIP-DD)

Recent progress in high-speed sequencing technology has revealed that tumors harbor novel mutations in a variety of genes including those for molecules involved in epigenetics and splicing, some of which were not categorized to previously thought malignancy-related genes. However, despite thorough identification of mutations in solid tumors and hematological malignancies, how these mutations induce cell transformation still remains elusive. In addition, each tumor usually contains multiple mutations or sometimes consists of multiple clones, which makes functional analysis difficult. Fifteen years ago, it was proposed that combination of two types of mutations induce acute leukemia; Class I mutations induce cell growth or inhibit apoptosis while class II mutations block differentiation, co-operating in inducing acute leukemia. This notion has been proven using a variety of mouse models, however most of recently found mutations are not typical class I/II mutations. Although some novel mutations have been found to functionally work as class I or II mutation in leukemogenesis, the classical class I/II theory seems to be too simple to explain the whole story. We here overview the molecular basis of hematological malignancies based on clinical and experimental results, and propose a new working hypothesis for leukemogenesis.

A C-terminal mutant of CCAAT-enhancer-binding protein α (C/EBPα-Cm) downregulates Csf1r, a potent accelerator in the progression of acute myeloid leukemia with C/EBPα-Cm

Two types of CCAAT-enhancer-binding protein α (C/EBPα) mutants are found in acute myeloid leukemia (AML) patients: N-terminal frame-shift mutants (C/EBPα-N(m)) generating p30 as a dominant form and C-terminal basic leucine zipper domain mutants (C/EBPα-C(m)). We have previously shown that C/EBPα-K304_R323dup belonging to C/EBPα-C(m), but not C/EBPα-T60fsX159 belonging to C/EBPα-N(m), alone induced AML in mouse bone marrow transplantation (BMT) models. Here we show that various C/EBPα-C(m) mutations have a similar, but not identical, potential in myeloid leukemogenesis. Notably, like C/EBPα-K304_R323dup, any type of C/EBPα-C(m) tested (C/EBPα-S299_K304dup, K313dup, or N321D) by itself induced AML, albeit with different latencies after BMT; C/EBPα-N321D induced AML with the shortest latency. By analyzing the gene expression profiles of C/EBPα-N321D- and mock-transduced c-kit(+)Sca-1(+)Lin(-) cells, we identified Csf1r as a gene downregulated by C/EBPα-N321D. In addition, leukemic cells expressing C/EBPα-C(m) exhibited low levels of colony stimulating factor 1 receptor in mice. On the other hand, transduction with C/EBPα-N(m) did not influence Csf1r expression in c-kit(+)Sca-1(+)Lin(-) cells, implying a unique role for C/EBPα-C(m) in downregulating Csf1r. Importantly, Csf1r overexpression collaborated with C/EBPα-N321D to induce fulminant AML with leukocytosis in mouse BMT models to a greater extent than did C/EBPα-N321D alone. Collectively, these results suggest that C/EBPα-C(m)-mediated downregulation of Csf1r has a negative, rather than a positive, impact on the progression of AML involving C/EBPα-C(m), which might possibly be accelerated by additional genetic and/or epigenetic alterations inducing Csf1r upregulation.

SETBP1 mutations drive leukemic transformation in ASXL1-mutated MDS

Mutations in ASXL1 are frequent in patients with myelodysplastic syndrome (MDS) and associated with adverse survival yet the molecular pathogenesis of ASXL1 mutations are not fully understood. Recently it has been found that deletion of Asxl1 or expression of C-terminal-truncating ASXL1 mutations (ASXL1-MT) inhibit myeloid differentiation and induce MDS-like disease in mice. Here, we find that SETBP1 mutations (SETBP1-MT) are enriched among patients with ASXL1-mutated MDS patients and associated with increased incidence of leukemic transformation as well as shorter survival, suggesting SETBP1-MT play a critical role in leukemic transformation of MDS. We identify that SETBP1-MT inhibit ubiquitination and subsequent degradation of SETBP1, resulting in increased expression. Expression of SETBP1-MT, in turn, inhibited Pp2a activity, leading to Akt activation and enhanced expression of posterior Hoxa genes in ASXL1 mutant cells. Biologically, SETBP1-MT augmented ASXL1-MT-induced differentiation block, inhibited apoptosis, and enhanced myeloid colony output. SETBP1-MT collaborated with ASXL1-MT in inducing AML in vivo. The combination of ASXL1-MT and SETBP1-MT activated a stem cell signature and repressed the TGF-β signaling pathway, in contrast to the ASXL1-MT-induced MDS model. These data reveal that SETBP1-MT are critical drivers of ASXL1-mutated MDS and identify several deregulated pathways as potential therapeutic targets in high-risk MDS.

Erythromycin ameliorates renal injury via anti-inflammatory effects in experimental diabetic rats

AIMS/HYPOTHESIS

Recent studies have shown that the inflammatory process is involved in the pathogenesis of diabetic nephropathy. Fourteen-membered ring macrolides, including erythromycin, have anti-inflammatory, as well as antibacterial effects. The aim of this study was to investigate the renoprotective effects of erythromycin in streptozotocin (STZ)-induced diabetic rats.

METHODS

STZ-induced diabetic rats were treated orally with erythromycin (5 mg/kg body weight) or vehicle every day for 8 weeks. To evaluate the effect of erythromycin treatment, we measured urinary albumin excretion, and examined the following in the kidney: histological changes, the expression of intercellular adhesion molecule-1 (ICAM-1), macrophage infiltration, and nuclear factor-kappa B (NF-kappaB) activity.

RESULTS

Erythromycin significantly reduced urinary albumin excretion without affecting blood glucose levels and blood pressure. Erythromycin also attenuated glomerular hypertrophy, mesangial expansion, macrophage infiltration and ICAM-1 expression in renal tissues. The expression of the gene encoding TGFB1 (also known as TGF-beta1), type IV collagen protein production and NF-kappaB activity in renal tissues were increased in diabetic rats and reduced by erythromycin treatment.

CONCLUSIONS/INTERPRETATION

Erythromycin prevented renal injuries without changes of blood glucose levels and blood pressure in experimental diabetic rats. These results suggest that the renoprotective effects of erythromycin are based on its anti-inflammatory effect via suppression of NF-kappaB activation. Modulation of microinflammation with erythromycin may provide a new approach for diabetic nephropathy.

Connection mechanism of physical-contact optical fiber connectors with spherical convex polished ends

We present an experimental and analytical investigation of the connection mechanism of physical-contact optical-fiber connectors with spherical convex polished ends and confirm that reducing the curvature radius of the spherical convex ferrule end face is effective for establishing a stable connection with slight axial compressive force on the ferrules.