anti-AML Agents Research Articles

Emetine induces oxidative stress, cell differentiation and NF-κB inhibition, suppressing AML stem/progenitor cells

Acute myeloid leukemia (AML) is a fatal malignancy of the blood and bone marrow. Leukemic stem cells (LSCs) are a rare subset of leukemic cells that promote the development and progression of AML, and eradication of LSCs is critical for effective control of this disease. Emetine is an FDA-approved antiparasitic drug with antitumor properties; however, little is known about its potential against LSCs. Herein, we explored the antileukemic potential of emetine, focusing on its effects on AML stem/progenitor cells. Emetine exhibited potent cytotoxic activity both in hematologic and solid cancer cells and induced AML cell differentiation. Emetine also inhibited AML stem/progenitor cells, as evidenced by decreased expression of CD34, CD97, CD99, and CD123 in KG-1a cells, indicating anti-AML stem/progenitor cell activities. The administration of emetine at a dosage of 10 mg/kg for two weeks showed no significant toxicity and significantly reduced xenograft leukemic growth in vivo. NF-κB activation was reduced in emetine-treated KG-1a cells, as shown by reduced phospho-NF-κB p65 (S529) and nuclear NF-κB p65. DNA fragmentation, YO-PRO-1 staining, mitochondrial depolarization and increased levels of active caspase-3 and cleaved PARP (Asp214) were detected in emetine-treated KG-1a cells. Moreover, treatment with the pancaspase inhibitor Z-VAD(OMe)-FMK partially prevented the apoptotic cell death induced by emetine. Emetine treatment also increased cellular and mitochondrial reactive oxygen species, and emetine-induced apoptosis in KG-1a cells was partially prevented by the antioxidant N-acetylcysteine, indicating that emetine induces apoptosis, at least in part, by inducing oxidative stress. Overall, these studies indicate that emetine is a novel potential anti-AML agent with promising activity against stem/progenitor cells, encouraging the development of further studies aimed at its clinical application.

TAK-981, a SUMOylation inhibitor, suppresses AML growth immune-independently.

Acute myeloid leukemia (AML) generally has an unsatisfactory prognosis despite the recent introduction of new regimens, including targeted agents and antibodies. To find a new druggable pathway, we performed integrated bioinformatic pathway screening on large OHSU and MILE AML databases, discovered the SUMOylation pathway, and validated it independently with an external data set (totaling 2959 AML and 642 normal sample data). The clinical relevance of SUMOylation in AML was supported by its core gene expression which is correlated with patient survival, European LeukemiaNet 2017 risk classification, and AML-relevant mutations. TAK-981, a first-in-class SUMOylation inhibitor currently under clinical trials for solid tumors, showed antileukemic effects with apoptosis induction, cell-cycle arrest, and induction of differentiation marker expression in leukemic cells. It exhibited potent nanomolar activity, often stronger than that of cytarabine, which is part of the standard of care. TAK-981's utility was further demonstrated in invivo mouse and human leukemia models as well as patient-derived primary AML cells. Our results also indicate direct and cancer cell-inherent anti-AML effects by TAK-981, different from the type 1 interferon and immune-dependent mechanism in a previous solid tumor study. Overall, we provide a proof-of-concept for SUMOylation as a new targetable pathway in AML and propose TAK-981 as a promising direct anti-AML agent. Our data should prompt studies on optimal combination strategies and transitions to clinical trials in AML.

2,4-Diaryl-pyrimido[1,2-a]benzimidazole derivatives as novel anticancer agents endowed with potent anti-leukemia activity: Synthesis, biological evaluation and kinase profiling

Acute myeloid leukemia (AML) stands as one of the most aggressive type of human cancer that can develop rapidly and thus requires immediate management. In the current study, the development of novel derivatives of pyrimido[1,2-a]benzimidazole (5a-p) as potential anti-AML agents is reported. The prepared compounds 5a-p were inspected for their in vitro anti-tumor activity at NCI-DTP and subsequently 5h was selected for full panel five-dose screening to assess its TGI, LC50 and GI50 values. Compound 5h showed effective anti-tumor activity at low micromolar concentration on all tested human cancer cell lines with GI50 range from 0.35 to 9.43 μM with superior sub-micromolar activity towards leukemia. Furthermore, pyrimido[1,2-a]benzimidazoles 5e-l were tested on a panel ofhuman acute leukemia cell lines, namely HL60, MOLM-13, MV4-11, CCRF-CEM and THP-1, where 5e-h reached single-digit micromolar GI50 values for all the tested cell lines. All prepared compounds were first tested for inhibitory action against the leukemia-associated mutant FLT3-ITD, as well as against ABL, CDK2, and GSK3 kinases, in order to identify the kinase target for the herein described pyrimido[1,2-a]benzimidazoles. However, the examined molecules disclosed non-significant activity against these kinases. Thereafter, a kinase profiling on a panel of 338 human kinases was then used to discover the potential target. Interestingly, pyrimido[1,2-a]benzimidazoles 5e and 5h significantly inhibited BMX kinase. Further investigation for the effect on cell cycle of HL60 and MV4-11 cells and caspase 3/7 activity was also performed. In addition, the changes in selected proteins (PARP-1, Mcl-1, pH3-Ser10) associated with cell death and viability were analyzed in HL60 and MV4-11 cells by immunoblotting.

From Serendipity to Rational Identification of the 5,6,7,8-Tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4(3H)-one Core as a New Chemotype of AKT1 Inhibitors for Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic malignancy whose prognosis is globally poor. In more than 60% of AML patients, the PI3K/AKTs/mTOR signaling pathway is aberrantly activated because of oncogenic driver alterations and further enhanced by chemotherapy as a mechanism of drug resistance. Against this backdrop, very recently we have started a multidisciplinary research project focused on AKT1 as a pharmacological target to identify novel anti-AML agents. Indeed, the serendipitous finding of the in-house compound T187 as an AKT1 inhibitor has paved the way to the rational identification of new active small molecules, among which T126 has emerged as the most interesting compound with IC50 = 1.99 ± 0.11 μM, ligand efficiency of 0.35, and a clear effect at low micromolar concentrations on growth inhibition and induction of apoptosis in AML cells. The collected results together with preliminary SAR data strongly indicate that the 5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4(3H)-one derivative T126 is worthy of future biological experiments and medicinal chemistry efforts aimed at developing a novel chemical class of AKT1 inhibitors as anti-AML agents.

Synthesis of new pyrazolo[4,3-a]phenanthridine Pim-1 inhibitors and evaluation of their cytotoxic activity towards the MOLM-13 acute myeloid leukemia cell line

We synthesized new analogues of the anti-AML agent VS-II-173. We studied the effect of the substitution at the 1- and 5-positions of the pyrazolo[4,3-a]phenanthridine scaffold on Pim-1 kinase inhibition and cytotoxicity against AML MOLM-13 cells. We found that compounds 20 and 21, substituted at the 1-position exhibited stronger Pim-1 inhibition together with a high potency toward MOLM-13 cells, associated with apoptosis induction and selectivity over non-cancerous NRK cells.

PB1790: ABCB1 AS A POTENTIAL BENEFICIAL TARGET OF MIDOSTAURIN IN ACUTE MYELOID LEUKEMIA

Background: In AML, therapeutic outcome of anthracycline-based induction therapy often can be compromised by a resistant phenotype associated with overexpression of ABCB1 transporters. Novel anti-AML agent, midostaurin, was designed to aim at multiple targets including FLT3 mutation. Besides, it was also identified as ABCB1 inhibitor. Aims: To evaluate ABCB1 efflux activity and expression in primary AML samples in relation to multiple clinical parameters and investigate ABCB1 regulation by microRNA. Methods: ABCB1 gene expression was absolutely quantified in 28 primary AML samples collected prior to any treatment. Efflux activity was examined using combination of mitoxantrone (ABCB1 substrate) and midostaurin (ABCB1/FLT3 inhibitor). Results were compared in molecular classes defined by CD34 marker, FLT3-ITD and NPM1 mutations, ELN risk classification and (un)achieved complete remission (CR). Enhancement of daunorubicin proapoptotic effect mediated by midostaurin was determined in HL-60 wt and HL-60 overexpressing ABCB1. ABCB1 regulation by microRNAs (miR-9, miR-27a, miR-331) was evaluated by ddPCR and correlated with ABCB1 efflux activity. Results: High ABCB1 expression was associated with unachieved CR, adverse ELN risk and CD34 positivity. ABCB1 efflux activity was observed in a functional study when mitoxantrone accumulation increased as a direct consequence of midostaurin in CD34+ AML and patients with unachieved CR. ABCB1 efflux activity and expression were found to be linked to miR-9 downregulation Summary/Conclusion: We propose therapeutic value of midostaurin for drug-resistant patients beyond the FLT3 inhibition based on ABCB1 expression and CD34 positivity. We also propose miR-9 as a predictive ABCB1-related biomarker that could be helpful in identifying ABCB1-resistant AML phenotype.

Synergistic Combination Activity of the Novel GSPT1 Degrader CC-90009 in Acute Myeloid Leukemia Models

Introduction: CC-90009 is a novel cereblon E3 ligase modulator (CELMoD ®) agent that is a first-in-class degrader of translation termination factor G1 to S phase transition 1 (GSPT1). CC-90009 has demonstrated antileukemic activity as a single agent and is currently under investigation in patients with acute myeloid leukemia (AML; NCT02848001). Treatment with CC-90009 led to rapid reductions in peripheral and bone marrow blasts, and demonstrated preliminary promising efficacy, including several complete remissions, in patients with relapsed or refractory AML. Here, we describe the identification and preclinical activity of select anti-AML agents as potential combination partners of CC-90009 to further improve its efficacy and therapeutic index. Based on these results, the combination activity of CC-90009 with venetoclax (VEN)/azacitidine (AZA) is being evaluated in a phase 1/2 trial in patients with AML (NCT04336982).Methods: A high-throughput cell viability screen was performed to identify synergistic partners of CC-90009. AML cell lines (HL-60, HNT-34, KG-1, ML-2, NOMO-1, MOLM-13, MV4-11, F-36P, OCI-AML2, OCI-AML3) were treated with CC-90009 in combination with > 70 compounds, including standard anti-AML agents, tyrosine kinase inhibitors (TKIs), unfolded protein response inducers, transcription inhibitors, and epigenetic agents. MOLM-13 and MV4-11 are fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) cell lines. Hits were validated in a colony formation (CF) assay using primary AML cells and bone marrow mononuclear cells (BMMC) from healthy donors. Synergy of the combination partners with CC-90009 was further assessed in AML patient-derived xenograft (PDX) models. Synergy between the isocitrate dehydrogenase 2 (IDH2) inhibitor enasidenib and CC-90009 was evaluated in a TF-1 erythroleukemia cell line overexpressing IDH2 R140Q mutant, and an IDH2 R140Q PDX model, AM7577.Results: Our high-throughput combination screen revealed multiple TKIs, epigenetic agents, and pro-apoptotic agents as potential combination partners of CC-90009 in AML cell lines. FLT3 inhibitors, including sunitinib, pexidartinib, midostaurin, lestaurtinib, crenolanib, and gilteritinib, synergized with CC-90009 to reduce viability in FLT3-ITD AML cell lines MV4-11 and MOLM-13. Similarly, the B-cell lymphoma 2 (BCL2) inhibitor VEN potentiated CC-90009-induced apoptosis and accelerated cell-autonomous killing. Reduction in levels of MCL-1, an anti-apoptotic factor, by CC-90009 most likely contributed to the synergy with VEN.We prioritized the evaluation of FLT3, BCL2, and IDH2 inhibitors as partners of CC-90009. In CF assays, midostaurin enhanced the inhibitory effect of CC-90009 in primary AML cells, without augmenting the effect of CC-90009 in CD34+ BMMC from healthy donors. Similarly, VEN enhanced the reduction in CF by CC-90009 in AML patient-derived BMMC without exacerbating the decrease in CF by CC-90009 in BMMC from healthy donors.We characterized FLT3 inhibitor/CC-90009 and BCL2 inhibitor/AZA/CC-90009 combinations in a FLT3-ITD PDX murine model, PDX1. The FLT3 inhibitor quizartinib significantly prolonged survival when combined with CC-90009 compared with either agent alone (P < 0.001). Similarly, VEN/AZA/CC-90009 combination markedly extended survival compared with single agents or VEN/AZA doublets (P < 0.001).The synergy between CC-90009 and epigenetic modulators was validated and further characterized in customized cell differentiation assays. Addition of CC-90009 to enasidenib, a mutant IDH2 inhibitor, enhanced differentiation and killing of CD34+ stem and progenitor cells, and increased differentiated CD235a+ erythroblasts, compared with enasidenib alone in a TF-1 cell line overexpressing IDH2 R140Q. Enasidenib/CC-90009 combination treatment reduced CD45+ malignant populations and increased differentiated CD14+ cells, leading to significantly prolonged animal survival in an IDH2 R140Q PDX model, AM7577, compared with either agent alone (P < 0.0001).Conclusion: Using a high-throughput combination screen, we identified rational combination partners that synergize with CC-90009 in in vitro and in vivo AML models. Collectively, these results support the clinical evaluation of CC-90009 in combination with FLT3, BCL2, and IDH2 inhibitors to further improve treatment outcomes for patients with AML. DisclosuresPierce: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Yao: Bristol Myers Squibb: Consultancy, Current equity holder in publicly-traded company, Ended employment in the past 24 months, Research Funding. Pace: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties. Wang: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Flandin-Blety: Bristol Myers Squibb: Current Employment. Benitez: Bristol Myers Squibb: Current Employment. Guarinos: Bristol Myers Squibb: Current Employment. Hoffmann: Bristol Myers Squibb: Current Employment. Carrancio: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Pourdehnad: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties.

Borax Pentahydrate and Disodium Pentaborate Decahydrate Are Candidates as Anti-leukemic Drug Components by Inducing Apoptosis and Changing Bax/Bcl-2 Ratio in HL-60 Cell Line

Acute myeloid leukemia (AML) is the most common form of acute leukemia and has the lowest 5-year survival rates. Current treatment strategies do not meet the expectations also. Therefore, there is a need to improve therapeutic approaches still. Boron, which is a natural trace element in human diet, is gaining attention with its important roles in cellular processes for the development of new anti-cancer drug candidates. For instance, bortezomib, a dipeptidyl boronic acid, has encouraging results in the treatment of multiple myeloma and mantle cell lymphoma. However, severe toxic effects and resistance development are the limitations to its application for AML treatment. Hence, the development of alternative boron-derived anti-AML agents is unmet need. Therefore, we aimed to evaluate anti-leukemic effect of two promising boron compounds, borax pentahydrate (BP) and disodium pentaborate decahydrate (DPD), and comparison of each other in terms of the capacity to trigger apoptosis on acute promyelocytic leukemia cells (HL-60). Cell viability was assessed by MTT assay. Apoptotic effects of the boron compounds on HL-60 cells were evaluated by annexin V/propidium iodide dyes and caspase 3/7 activity assay by flow cytometry. In addition, Bax/Bcl-2 and cleaved PARP levels were detected by western blotting. Although BP showed greater apoptosis-inducing capacity, we observed that both DPD (6mM) and BP (24mM) treatment showed anti-leukemic effect by triggering apoptotic pathway through increasing Bax/Bcl-2 ratio for the first time. Our study suggests that BP and DPD are the promising candidates for anti-AML drug development research, which may be confirmed by further wide-spectrum studies.

Pharmacophore-inspired discovery of FLT3 inhibitor from kimchi

Globally consumed kimchi is manufactured through fermenting cruciferous vegetables containing indole glucosinolates (IG). But few reports describe the IG metabolism during the fermentation. Here, we show that indole-3-carbinol (I3C), a breakdown product of IG, is transformed during the kimchi fermentation into 3,3′-diindolylmethane (DIM) and 2-(indol-3-ylmethyl)-3,3′-diindolylmethane (LTr1). LTr1 was found to kill the acute myeloid leukemia (AML) cells with FMS-like tyrosine kinase 3 (FLT3) receptor mutations, by inhibiting the FLT3 phosphorylation and the expression of downstream proteins (STAT5, ERK, and AKT). In the immune-depleted mice xenografted with human MV4-11 cells, LTr1 was demonstrated to reduce the tumor growth and synergize with sorafenib, an anti-AML agent in clinic. The work updates the chemical and biological knowledge about kimchi, and in particular establishes LTr1 as an FLT3 inhibitor that is effective and synergistic with sorafenib in treating AML.

Anti-leukaemia effects of leonurine in vitro and in vivo.

The present study was conducted to explore the anti-acute myeloid leukaemia (AML) effects of leonurine. HL-60 and U-937 cells were used to assess the antileukaemia effect of leonurine in vitro, and HL-60 and U-937 xenograft nude mice were used to evaluate its antitumour effect in vivo. Leonurine inhibited the proliferation of HL-60 and U-937 cells in a time- and dose-dependent manner. Moreover, leonurine therapy prevented the growth of tumours in both xenograft animal models. Leonurine could induce apoptosis in HL-60 and U-937 cells. The cytotoxic effects of leonurine on HL-60 and U-937 cells were associated with an increased ratio of Bax/Bcl-2, activation of caspase-3, caspase-8 and caspase-9, and increased expression of cytochrome c in the cytoplasm. Leonurine inhibited activation of the PI3K/Akt pathway in HL-60 and U-937 cells by lowering the phosphorylation levels of PI3K and Akt. Our results indicate that leonurine is a potential anti-AML agent, and this activity may be associated with its repression of the phosphorylation of PI3K and Akt.

A novel dipeptide type inhibitor of the Wnt/β-catenin pathway suppresses proliferation of acute myelogenous leukemia cells

The Wnt/β-catenin pathway is an attractive target for the treatment of acute myelogenous leukemia (AML), since aberrant activation of the Wnt/β-catenin pathway contributes to carcinogenesis in various types of cancers including AML. Screening of an in-house compound library, constructed at Kyoto Pharmaceutical University, identified a novel compound designated “31” that was found to be an inhibitor of the Wnt/β-catenin pathway. The compound inhibited T-cell factor (TCF) activity in a TCF firefly luciferase-reporter assay and suppressed the proliferation of several human AML cell lines in a dose-dependent manner. Compound 31 arrested the cell cycle of AML cells at the G1 stage and induced apoptosis. Decrease in protein and mRNA expression level of Wnt pathway-related molecules was confirmed by the analyses of western blotting and quantitative reverse transcription-polymerase chain reaction. In addition, compound 31 combined with idarubicin synergistically inhibited the proliferation of AML cells. In conclusion, these results strongly suggest that compound 31 has potential as a novel anti-AML agent targeting the Wnt/β-catenin signaling pathway.

Advances in Azorella glabra Wedd. Extract Research: In Vitro Antioxidant Activity, Antiproliferative Effects on Acute Myeloid Leukemia Cells and Bioactive Compound Characterization

Azorella glabra Wedd. (AG) is traditionally used to treat gonorrhea or kidney’s problems. The antioxidant, antidiabetic, anticholinesterase and in vitro antitumor activities of AG extracts were recently reported. The aim of this work was to investigate anti-leukemic properties of AG chloroform fraction (AG CHCl3) and of its ten sub-fractions (I-X) and to identify their possible bioactive compounds. We determined their in vitro antioxidant activity using 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), nitric oxide (NO) and superoxide anion (SO) assays, and their phytochemical profile by spectrophotometric and LC-MS/MS techniques. I-X action on two acute myeloid leukemia (AML) cell lines viability, apoptosis and cell cycle were evaluated by MTS, western blotting and cytofluorimetric assays. Different polyphenol, flavonoid and terpenoid amount, and antioxidant activity were found among all samples. Most of I-X induced a dose/time dependent reduction of cell viability higher than parent extract. IV and VI sub-fractions showed highest cytotoxic activity and, of note, a negligible reduction of healthy cell viability. They activated intrinsic apoptotic pathway, induced a G0/G1 block in leukemic cells and, interestingly, led to apoptosis in patient AML cells. These activities could be due to mulinic acid or azorellane terpenoids and their derivatives, tentatively identified in both IV and VI. In conclusion, our data suggest AG plant as a source of potential anti-AML agents.

Semisynthetic Derivatives of Fradcarbazole A and Their Cytotoxicity against Acute Myeloid Leukemia Cell Lines.

Fourteen derivatives of the marine-derived fradcarbazole A were synthesized from staurosporine. Their structures were identified by NMR and high-resolution electrospray ionization mass spectrometry (HRESIMS). The derivatives were screened in vitro for antiproliferative activity against three human leukemic cell lines (MV4-11, HL-60, K562). All of the derivatives displayed cytotoxicity against the human FLT-3 internal tandem duplication (ITD) mutant acute myeloid leukemia (AML) cell line MV4-11 with IC50 values of 0.32-0.96 μM. The mechanism of action studies indicated that the most effective 3-chloro-5‴-fluorofradcarbazole A (6) induced apoptosis of the MV4-11 cells and arrested the cell cycle at the G0/G1 phase. Furthermore, compound 6 can reduce the expression of FLT-3, CDK2, and c-kit. The results suggest that 3-chloro-5‴-fluorofradcarbazole A (6) is a potential candidate for developing novel anti-AML agents in the future.

Abstract 5: Pre-clinical development of CDK9 inhibitor - LS007 for the treatment of acute myeloid leukemia

Abstract Acute myeloid leukemia (AML) is the most common form of acute leukaemia with an increasing incidence and dismal long-term prognosis with age. The most aggressive subtype, MLL-AML, is characterized by translocations of the mixed-lineage leukaemia gene (MLL) in chromosome band 11q23 and resistance to conventional chemotherapy with a short overall survival of only 9 months. Cyclin-dependent 9 (CDK9) activity is required for MLL-driven oncogenic transcription. Inhibition of CDK9 directly targets the transcriptional machinery required for MLL-fusion proteins (e.g. MLL-AF4, MLL-AF9 and MLL-ENL), thereby leading to apoptosis. We have developed a highly effective drug candidate - LS007 that inhibited CDK9 with a Ki = 4 nM. It suppressed proliferation and induced apoptosis in a range of AML cell lines and patient samples. LS007 was highly efficacious against several AML cell line xenografts and patient-derived xenografts, and well tolerated in mice after oral administration. In a Molm-13 xenograft model, after 21 days of orally daily dosing at 25 mg/kg and 50 mg/kg LS007 inhibited tumor growth (p &amp;lt; 0.001) with T/C = 44 % and 18 %, respectively. Similarly, in a HL-60 xenograft model, LS007 exhibited a significant tumor growth inhibition at 45 mg/kg and 60 mg/kg daily by oral administration with T/C = 40 % and 20 %, respectively. The pharmacokinetic profiles of LS007 was further assessed in the cynomolgus monkeys. After oral doses at the dose of 2, 4 and 8 mg/kg, LS007 was detected in the plasma with the maximum concentration (Cmax) from 55.9 to 279.5 ng/mL and the area under the plasma drug concentration-time graph (AUC) up to 1862.7 h·ng/mL. The mean terminal half-life (T 1/2) was around 3 h. LS007 possessed the favorable pharmacokinetic profiles with oral bioavailability F = 56% in the cynomolgus monkey (at dose 4 mg/kg), suggesting its therapeutic potential as an orally bioavailable anti-AML agent. The GLP- toxicological studies of LS007 in the cynomolgus monkey were completed, and the maximum tolerated doses were identified, which were used to estimate the safe starting dose for the Phase I clinical trials. With its excellent anti-cancer efficacy along with appreciable absorption and safety profiles, LS007 offers a very exciting prospect as a clinical development candidate. The application of Investigational New Drug (IND) has been approved allowing the commencement of clinical trials of LS007 in patients with AML. Citation Format: Wang Hui, Wang Shudong. Pre-clinical development of CDK9 inhibitor - LS007 for the treatment of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5.

Amino alkynylisoquinoline and alkynylnaphthyridine compounds potently inhibit acute myeloid leukemia proliferation in mice.

BackgroundAcute myeloid leukemia (AML) remains one of the most lethal, rarely cured cancers, despite decades of active development of AML therapeutics. Currently, the 5-year survival of AML patients is about 30% and for elderly patients, the rate drops to <10%. About 30% of AML patients harbor an activating mutation in the tyrosine kinase domain (TKD) of Fms-Like Tyrosine kinase 3 (FLT3) or a FLT3 internal tandem duplication (FLT3-ITD). Inhibitors of FLT3, such as Rydapt that was recently approved by the FDA, have shown good initial response but patients often relapse due to secondary mutations in the FLT3 TKD, like D835Y and F691 L mutations.MethodsAlkynyl aminoisoquinoline and naphthyridine compounds were synthesized via Sonogashira coupling. The compounds were evaluated for their in vitro and in vivo effects on leukemia growth.FindingsThe compounds inhibited FLT3 kinase activity at low nanomolar concentrations. The lead compound, HSN431, also inhibited Src kinase activity. The compounds potently inhibited the viability of MV4–11 and MOLM-14 AML cells with IC50 values <1 nM. Furthermore, the viability of drug-resistant AML cells harboring the D835Y and F691 L mutations were potently inhibited. In vivo efficacy studies in mice demonstrated that the compounds could drastically reduce AML proliferation in mice.InterpretationCompounds that inhibit FLT3 and downstream targets like Src (for example HSN431) are good leads for development as anti-AML agents.FundPurdue University, Purdue Institute for Drug Discovery (PIDD), Purdue University Center for Cancer Research, Elks Foundation and NIH P30 CA023168.

Identification of ortho-naphthoquinones as anti-AML agents by highly efficient oxidation of phenols

A straightforward method for synthesizing ortho-naphthoquinones was identified using an easily available cobalt–Schiff base complex. Efficient oxidation of phenols to ortho-naphthoquinones was useful in obtaining compounds with potent biological activity for the treatment of acute myeloid leukemia (AML). Among these compounds, the compound 4h effectively inhibited the proliferation of different AML cell lines in vitro. Further in vivo antitumor studies indicated that 4h at 40 mg/kg/d led to tumor regression in led to tumor regression in an MV4-11 xenograft model without evident toxicity. The cobalt-Schiff base complex was found to be an efficient catalyst in the transformation of phenols to ortho-quinones, and the compound 4h represents a potential scaffold to optimize the production of a treatment for AML.

Targeting of mTORC1/2 by dihydroevocarpine induces cytotoxicity in acute myeloid leukemia.

Interactions between the tumor cells and bone marrow (BM) microenvironment promote survival, growth, and chemoresistance of acute myeloid leukemia (AML). The mTOR pathway plays a key role in mediating the AML-BM microenvironment interactions. Here, we report the anti-AML activity of a natural monomer extracted from the Chinese medicinal herb Evodia rutaecarpa, dihydroevocarpine. Our results showed that dihydroevocarpine-induced cytotoxicity, apoptosis, and G0/G1 arrest in AML cells, and inhibited the tumor growth in an AML xenograft model. Importantly, our study revealed that the dihydroevocarpine treatment inhibited the mTOR pathway via suppressing the mTORC1/2 activity, and thus overcame the protective effect of the BM microenvironment on AML cells. Taken together, our findings suggest that dihydroevocarpine could be used as a potential anti-AML agent alone or a therapeutic adjunct in AML therapy, particularly in the presence of the BM microenvironment.

Mechanisms Underlying Superior Efficacy of Co-Targeting BET Proteins and Anti-Apoptotic BCL2 or MCL1 Protein Against AML Blast Progenitor Cells

Bromodomain extra-terminal (BET) protein (BETP) family of chromatin reader proteins includes BRD4 that binds to acetylated lysine in the active chromatin and transcription factors (TFs) at enhancers and promoters, as well as increases RNA pol II (RNAP2) mediated mRNA transcription of active oncogenes in AML. Disruption of binding and eviction of BRD4 from chromatin results in transcriptional attenuation of pro-growth and pro-survival oncoproteins. These include c-Myc, BCL2, MCL1, CDK6, while inducing p21, p27 and HEXIM1, thereby causing growth inhibition and apoptosis of AML blast progenitor cells (BPCs). Consistent with this, first generation BETP inhibitors (BETi) (e.g., OTX015) have been shown to reduce AML burden and induce clinical remissions, albeit in a minority of patients with AML. Recently, more potent BETis such as ABBV-075 (AbbVie Inc.) have been developed and are being investigated for their clinical efficacy in AML. Venetoclax (ABT-199, AbbVie) and A-1210477 bind and inhibit the antiapoptotic activity of BCL2 and MCL1, respectively, lowering the threshold for apoptosis in AML BPCs. Treatment with venetoclax alone, and in combinations with other anti-AML agents, is effective in inducing clinical remissions in AML. Here, we interrogated the epigenetic mechanisms underlying transcriptional repression due to BETi treatment, as well as determined the anti-AML activity of co-treatment with BETi and venetoclax or A-1210477 against AML BPCs. ATAC-Seq analysis showed that, in BETi-treated (over untreated control) AML BPCs, BETi treatment induced significantly greater perturbations in the accessible chromatin (number of peaks gained or lost), which were especially enriched for TF-binding sites for RUNX1, c-Myc, GATA2, PU.1 and ERG, especially in the DNA of BCL2, Bcl-xL, MCL1, MYC, BIM, PIM1, CDK6, BRD2/4, HEXIM1, CDKN1A, CEBPA and ITGAM. RNA-Seq analyses, followed by confirmation with QPCR, demonstrated that BETi treatment attenuated expression of MYC, BCL2, Bcl-xL and CDK6, while inducing mRNA expression of HEXIM1 and CDKN1A. BETi (ABBV-075) treatment also dose-dependently reduced protein levels of c-Myc, CDK6, MCL1 and BCL2, while inducing BIM, HEXIM1, CDKN1A and cleaved PARP levels in AML BPCs. This was associated with dose-dependent (10 to 250 nM) ABBV-075-induced apoptosis of cultured AML cell lines and AML BPCs. Whereas treatment with venetoclax (20 to 200 nM) or A-1210477 (1 to 10 µM) alone also induced apoptosis, co-treatment with ABBV-075 and venetoclax or A-1210477 synergistically induced apoptosis of AML BPCs, including CD34+ patient-derived AML BPCs (combination indices < 1.0). Notably, treatment with venetoclax significantly increased protein expression of MCL1 (p < 0.05), which has been recently reported as a potential mechanism of acquired-adaptive resistance to venetoclax. However, co-treatment with ABBV-075 significantly abrogated venetoclax-induced MCL-1 levels (p < 0.01), which likely contributed to the synergistic anti-AML activity of co-treatment with ABBV-075 and venetoclax against AML BPCs. We next determined the in vivo anti-AML efficacy of ABBV-075 and venetoclax in luciferase-transduced, AML BPCs (MOLM13) and patient-derived xenograft (PDX) models of AML BPCs engrafted in immune depleted (NSG) mice. Compared to treatment with either agent alone, co-treatment with ABBV-075 and venetoclax was significantly more effective in reducing AML cell burden (p < 0.001), without inducing toxicity, in AML BPC-engrafted NSG mice. Co-treatment with ABBV-075 and venetoclax also improved the median and overall survival of NSG mice engrafted with MOLM13 AML BPCs (p < 0.0001). Collectively, these pre-clinical findings elucidate the mechanistic rationale, and support evaluation of the clinical efficacy and safety of targeted co-treatment with BETi and BCL2 or MCL1 inhibitor in AML. DisclosuresKadia:Jazz: Consultancy, Research Funding; BMS: Research Funding; Novartis: Consultancy; Abbvie: Consultancy; Celgene: Research Funding; Celgene: Research Funding; Takeda: Consultancy; Novartis: Consultancy; Abbvie: Consultancy; Amgen: Consultancy, Research Funding; Jazz: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; BMS: Research Funding; Takeda: Consultancy; Pfizer: Consultancy, Research Funding. DiNardo:Karyopharm: Other: Advisory role; Medimmune: Other: Advisory role; Celgene: Other: Advisory role; Bayer: Other: Advisory role; Agios: Consultancy, Other: Advisory role; AbbVie: Consultancy, Other: Advisory role. Khoury:Stemline Therapeutics: Research Funding. Shen:AbbVie Inc: Employment. Konopleva:Stemline Therapeutics: Research Funding.

Reduced Chemosensitivity of FLT3/ITD Mutated Cells to Cytarabine and Quizartinib Under Hypoxic Conditions

Background: FLT3/ITD mutated AML is characterized by short remission duration and high relapse rates due to the survival of a small fraction of leukemic cells (LCs) that outlive initial therapy. There is compelling evidence that the hypoxic niche in the bone marrow (BM) provides a sanctuary where subpopulations of LCs evade cytotoxic therapy and acquire drug resistance. In order to define the mechanisms involved in this process, multiple studies have focused on the interactions between LCs and the BM microenvironment but less is known about to the role of hypoxia as a modulator of drug resistance. Hence, the effects of standard and investigational therapies under hypoxic conditions are largely unknown. Here, we investigated the cytotoxic response of FLT3/ITD-mutated cells to conventional and targeted therapy under normoxic (21% O2) and hypoxic (1% O2) conditions. Methods: Molm14 (M14) cells and primary cells from relapsed/refractory FLT3/ITD mutated AML patients were incubated in culture medium under normoxic and hypoxic conditions. Cytarabine (Cy) or Quizartinib (Quiz) were added as single agents at the indicated concentrations. After 48 hours proliferation and apoptosis assays were performed using MTT assays, annexin V/PI staining and FACS analysis (M14). Cells were also assessed for FLT3 protein and Hypoxia inducible factor (HIF) target gene expression by western blotting and PCR arrays (RT2 ProfilerTM PCR Array, Human Hypoxia Signaling Pathway Plus, Qiagen) (M14 and primary cells), respectively. Results: We found that M14 cells were significantly less susceptible to treatment under hypoxic conditions, both when exposed to Cy and targeted FLT3 inhibition with Quiz (Growth inhibition, 0.25nM Quiz: 8.5±4.2% (1% O2) vs. 22±2.5% (21% O2), p<.05; 49.6±2.5% (1% O2) vs. 58.1±2.3% (21% O2), n=8, p<.05; 0.25µM Cy: 3.7±2.5% (1% O2) vs. 14.4±1.5% (21% O2), p<.01; 1 µM Cy: 26.3±4.1% (1% O2) vs. 53.3±3.8% (21% O2), n=10-12, p<.001). In line with these findings, the apoptotic response of M14 cells to Cy treatment was significantly blunted under hypoxic conditions (Fold increase in apoptotic cells vs. untreated control, 1 µM: 5.7±0.8 fold [21% O2] vs. 2.7±0.5 fold [1% O2], n=4, p<.05). While not reaching the significance threshold, the trend was similar for the Quiz-treated cells. This effect was extended to primary, relapsed/refractory FLT3/ITD-mutated cells derived from patients (n=2) treated at our institution, where growth inhibition was consistently decreased in hypoxia at all doses of Cy and Quiz tested. Not unexpectedly, these primary cells required significantly higher doses compared to the established M14 cell line (1-10µM for Cy, and 50-200nM for Quiz). Importantly, Quiz appeared to be similarly effective in inactivating FLT3 activity under low and high oxygen tension. Therefore identifying tractable pro-survival genes induced by the low oxygen microenvironment should represent a viable strategy to increase the effectiveness of anti-leukemic agents. In order to identify such target candidates, we surveyed the effects of Quiz and Cy on a panel of 84 hypoxia-regulated genes using PCR arrays. Our preliminary studies revealed that while HIF pathway remains largely functional in the presence of Quiz or Cy, these agents severely blunt induction of several hypoxia genes (including Glucose transporter 1 [Glut1] and Carbonic Anhydrase 9 [CA9]) in both primary cells and M14 cells. Conclusions: 1.Hypoxia limits the cytotoxic effects of conventional and targeted therapeutic agents in primary and established FLT3/ITD mutated AML cells. 2. Quizartinib effectively abrogates FLT3 signaling under both normoxic and hypoxic conditions, indicating that other signaling pathways are critical for leukemic cell survival under reduced oxygen tension. 3. The induction of several potentially druggable HIF targets is disrupted by anti-AML agents, warranting the further investigation of combinational approaches between standard anti-AML agents and HIF targeted strategies. 4. Such therapeutic combinations are likely to be particularly effective undermicro-environmental stress conditions (e.g. severe hypoxia) thus addressing an unmet need in AML therapy. DisclosuresNo relevant conflicts of interest to declare.

Synthesis and Antileukemic Activities of Piperlongumine and HDAC Inhibitor Hybrids against Acute Myeloid Leukemia Cells.

Synergistic-to-additive antileukemic interactions of piperlongumine (PL) and HDAC inhibitor (HDACi) SAHA (Vorinostat) provide a compelling rationale to construct PL-HDACi hybrids, such as 1-58, which recapitulated the synergism between the parental compounds in high-risk and chemoresistant AML cells. Both PL and HDACi components, either in combination or in hybrid molecules, are essential for inducing significant DNA damage and apoptosis. Introducing C2-chloro substituent to 1-58 yielded 3-35 with increased cytotoxicity but decreased selectivity in noncancerous MCF-10A cells; eliminating C7-C8 olefin of PL obtained 3-31/3-98 scaffolds which were still more active than PL or SAHA in AML and were well-tolerated by MCF-10A cells. The HDACi function was crucial for modulating expression of DNA repair and apoptosis-related proteins. Collectively, PL and SAHA hybrids are potent, multifunctional anti-AML agents, acting in part, by interfering cellular GSH defense, suppressing expression of DNA repair and pro-survival proteins, and inducing expression of pro-apoptotic proteins.