bims-tremyl Biomed News
on Therapy resistance biology in myeloid leukemia
Issue of 2021‒02‒21
thirty-one papers selected by
Paolo Gallipoli
Barts Cancer Institute, Queen Mary University of London

  1. Haematologica. 2021 Jan 28.
      Acute myeloid leukemia patients with FLT3-ITD mutations have a high risk of relapse and death. FLT3 tyrosine kinase inhibitors improve overall survival, but their efficacy is limited and most patients who relapse will ultimately die of the disease. Even with potent FLT3 inhibition, the disease persists within the bone marrow microenvironment, mainly due to bone marrow stroma activating parallel signaling pathways that maintain pro-survival factors. BET inhibitors suppress pro-survival factors such as MYC and BCL2, but these drugs thus far have shown only limited single-agent clinical potential. We demonstrate here, using pre-clinical and clinical correlative studies, that the novel 4-azaindole derivative, PLX51107, has BET-inhibitory activity in vitro and in vivo. The combination of BET and FLT3 inhibition induces a synergistic antileukemic effect in a murine xenograft model of FLT3-ITD AML, and against primary FLT3-ITD AML cells co-cultured with bone marrow stroma. Using suppression of MYC as a surrogate for BET inhibition, we demonstrate BET inhibition in human patients. The short plasma half-life of PLX51107 results in intermittent target inhibition to enable tolerability while overcoming the protective effect of the microenvironment. Mechanistically, the synergistic cytotoxicity is associated with suppression of key survival genes such as MYC. These data provide the scientific rationale for a clinical trial of a BET plus FLT3 inhibitor for the treatment of relapsed/refractory FLT3-ITD AML. A clinical trial of PLX51107 as monotherapy in patients with different malignancies is underway and will be reported separately.
  2. Sci Adv. 2021 Feb;pii: eabe4038. [Epub ahead of print]7(8):
      The extensive drug resistance requires rational approaches to design personalized combinatorial treatments that exploit patient-specific therapeutic vulnerabilities to selectively target disease-driving cell subpopulations. To solve the combinatorial explosion challenge, we implemented an effective machine learning approach that prioritizes patient-customized drug combinations with a desired synergy-efficacy-toxicity balance by combining single-cell RNA sequencing with ex vivo single-agent testing in scarce patient-derived primary cells. When applied to two diagnostic and two refractory acute myeloid leukemia (AML) patient cases, each with a different genetic background, we accurately predicted patient-specific combinations that not only resulted in synergistic cancer cell co-inhibition but also were capable of targeting specific AML cell subpopulations that emerge in differing stages of disease pathogenesis or treatment regimens. Our functional precision oncology approach provides an unbiased means for systematic identification of personalized combinatorial regimens that selectively co-inhibit leukemic cells while avoiding inhibition of nonmalignant cells, thereby increasing their likelihood for clinical translation.
  3. Front Pharmacol. 2020 ;11 632809
      Chemotherapeutic patients with leukemia often relapse and produce drug resistance due to the existence of leukemia stem cells (LSCs). Fibroblast growth factor receptor 3 (FGFR3) signaling mediates the drug resistance of LSCs in chronic myeloid leukemia (CML). However, the function of FGFR3 in acute myeloid leukemia (AML) is less understood. Here, we identified that the loss of FGFR3 reprograms MLL-AF9 (MA)-driven murine AML cells into weakly pathogenic CD117-positive leukemia stem-like cells by activating the FGFR1-ERG signaling pathway. FGFR3 deletion significantly inhibits AML cells engraftment in vivo and extends the survival time of leukemic mice. FGFR3 deletion sharply decreased the expression of chemokines and the prolonged survival time in mice receiving FGFR3-deficient MA cells could be neutralized by overexpression of CCL3. Here we firstly found that FGFR3 had a novel regulatory mechanism for the stemness of LSCs in AML, and provided a promising anti-leukemia approach by interrupting FGFR3.
    Keywords:  CCL3 chemokine; FGFR1; erg; fibroblast growth factor receptor 3; leukemia (acute myeloid); stem-like cancer cells
  4. Leukemia. 2021 Feb 15.
      There is increasing interest in targeting CD33 in malignant and non-malignant disorders. In acute myeloid leukemia, longer survival with the CD33 antibody-drug conjugate gemtuzumab ozogamicin (GO) validates this strategy. Still, GO benefits only some patients, prompting efforts to develop more potent CD33-directed therapeutics. As one limitation, CD33 antibodies typically recognize the membrane-distal V-set domain. Using various artificial CD33 proteins, in which this domain was differentially positioned within the extracellular portion of the molecule, we tested whether targeting membrane-proximal epitopes enhances the effector functions of CD33 antibody-based therapeutics. Consistent with this idea, a CD33V-set/CD3 bispecific antibody (BsAb) and CD33V-set-directed chimeric antigen receptor (CAR)-modified T cells elicited substantially greater cytotoxicity against cells expressing a CD33 variant lacking the entire C2-set domain than cells expressing full-length CD33, whereas cytotoxic effects induced by GO were independent of the position of the V-set domain. We therefore raised murine and human antibodies against the C2-set domain of human CD33 and identified antibodies that bound CD33 regardless of the presence/absence of the V-set domain ("CD33PAN antibodies"). These antibodies internalized when bound to CD33 and, as CD33PAN/CD3 BsAb, had potent cytolytic effects against CD33+ cells. Together, our data provide the rationale for further development of CD33PAN antibody-based therapeutics.
  5. Cell Rep. 2021 Feb 16. pii: S2211-1247(21)00064-4. [Epub ahead of print]34(7): 108751
      The myeloid tumor suppressor KMT2C is recurrently deleted in myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), particularly therapy-related MDS/AML (t-MDS/t-AML), as part of larger chromosome 7 deletions. Here, we show that KMT2C deletions convey a selective advantage to hematopoietic stem cells (HSCs) after chemotherapy treatment that may precipitate t-MDS/t-AML. Kmt2c deletions markedly enhance murine HSC self-renewal capacity without altering proliferation rates. Haploid Kmt2c deletions convey a selective advantage only when HSCs are driven into cycle by a strong proliferative stimulus, such as chemotherapy. Cycling Kmt2c-deficient HSCs fail to differentiate appropriately, particularly in response to interleukin-1. Kmt2c deletions mitigate histone methylation/acetylation changes that accrue as HSCs cycle after chemotherapy, and they impair enhancer recruitment during HSC differentiation. These findings help explain why Kmt2c deletions are more common in t-MDS/t-AML than in de novo AML or clonal hematopoiesis: they selectively protect cycling HSCs from differentiation without inducing HSC proliferation themselves.
    Keywords:  HSC exhaustion; Kmt2c; MLL3; hematopoietic stem cell; interleukin-1; self-renewal; therapy-related leukemia
  6. Aging (Albany NY). 2021 Feb 11. 13
      Acute myeloid leukemia (AML) is a malignancy of hematopoietic stem cells. Although many candidate genes such as CEBPA, FLT3, IDH1, and IDH2 have been associated with AML initiation and prognosis, the molecular mechanisms underlying this disease remain unclear. In this study, we used a systemic co-expression analysis method, namely weighted gene co-expression network analysis (WGCNA), to identify new candidate genes associated with adult AML progression and prognosis. We identified around 5,138 differentially expressed genes (DEGs) between AML samples (from The Cancer Genome Atlas database) and normal control samples (from the Genotype-Tissue Expression database). WGCNA identified nine co-expression modules with significant differences based on the DEGs. Among modules, the turquoise and blue ones were the most relevant to AML (P-value: turquoise 0, blue 4.64E-77). GO term and KEGG pathway analyses revealed that pathways that are commonly dysregulated in AML were all enriched in the blue and turquoise modules. A total of 15 hub genes were identified to be crucial for AML progression. PIVOT analysis revealed non-coding RNAs, transcriptional factors, and drugs associated with the hub genes. Finally, survival analysis revealed that one of the hub genes, CEACAM5, was significantly associated with AML prognosis and could serve as a potential target for AML treatment.
    Keywords:  AML; WGCNA; hub genes
  7. Blood. 2021 Feb 17. pii: blood.2020007626. [Epub ahead of print]
      In the international randomized phase III RATIFY trial, the multi-kinase inhibitor midostaurin significantly improved overall and event-free survival in patients 18-59 years of age with FLT3-mutated acute myeloid leukemia (AML). However, only 59% of patients on the midostaurin arm achieved protocol-specified complete remission (CR) and almost half of patients achieving CR relapsed. To explore underlying mechanisms of resistance, we studied patterns of clonal evolution in patients with FLT3-internal tandem duplications (ITD) positive AML who were entered on the RATIFY or the AMLSG 16-10 trial and received treatment with midostaurin. To this end, paired samples from 54 patients obtained at time of diagnosis and at time of either relapsed or refractory disease were analyzed using conventional Genescan-based testing for FLT3-ITD as well as whole exome sequencing. At the time of disease resistance or progression, almost half of the patients (46%) became FLT3-ITD negative, but acquired mutations in signaling pathways (e.g. MAPK), thereby providing a new proliferative advantage. In cases with FLT3-ITD persistence, the selection of resistant ITD-clones was found in 11% as potential drivers of disease. In 32% of cases, no FLT3-ITD mutational change was observed suggesting either resistance mechanisms bypassing FLT3-inhibition or loss of midostaurin inhibitory activity due to inadequate drug levels. In summary, our study provides novel insights into the clonal evolution and resistance mechanisms of FLT3-ITD mutated AML under treatment with midostaurin in combination with intensive chemotherapy.
  8. Front Oncol. 2020 ;10 588641
      The treatment of chronic myeloid leukemia (CML) with BCR-ABL tyrosine kinase inhibitors (TKIs), such as imatinib, has yielded clinical success. However, the direct targeting of BCR-ABL does not eradicate CML cells expressing mutant BCR-ABL, especially the T315I mutation in BCR-ABL. Moreover, increasing mutations were identified in BCR-ABL domain, resulting in TKIs resistance recently. It is necessary to find BCR-ABL-independent target for treating CML patients with various mutations, including T315I mutation in BCR-ABL. The dichotomous behavior of CREB binding protein (CBP) and E1A protein (p300), recruited by β-catenin associated with self-renewal and differentiation, have been identified in hematopoietic stem cells, respectively. In this study, CBP was aberrantly expressed in CML cells on the basis of Oncomine dataset. The β-catenin bound with much more CBP than p300 in CML cells. Down-regulation of CBP inhibited cell proliferation capacity and increased the binding of β-catenin to p300, thus promoting cell differentiation and p53-dependent cell senescence in CML cells with either wild type or T315I mutant BCR-ABL in vitro and in vivo models. These demonstrate CBP blockage can be developed for the treatment of CML independent of BCR-ABL mutation status including T315I.
    Keywords:  CREB binding protein; cell differentiation; cell senescence; chronic myeloid leukemia; tyrosine kinase inhibitors resistance
  9. PLoS One. 2021 ;16(2): e0247093
      BACKGROUND: FLT3 mutation is present in 25-30% of all acute myeloid leukemias (AML), and it is associated with adverse outcome. FLT3 inhibitors have shown improved survival results in AML both as upfront treatment and in relapsed/refractory disease. Curiously, a variable proportion of wild-type FLT3 patients also responded to these drugs.METHODS: We analyzed 6 different transcriptomic datasets of AML cases. Differential expression between mutated and wild-type FLT3 AMLs was performed with the Wilcoxon-rank sum test. Hierarchical clustering was used to identify FLT3-mutation like AMLs. Finally, enrichment in recurrent mutations was performed with the Fisher's test.
    RESULTS: A FLT3 mutation-like gene expression pattern was identified among wild-type FLT3 AMLs. This pattern was highly enriched in NPM1 and DNMT3A mutants, and particularly in combined NPM1/DNMT3A mutants.
    CONCLUSIONS: We identified a FLT3 mutation-like gene expression pattern in AML which was highly enriched in NPM1 and DNMT3A mutations. Future analysis about the predictive role of this biomarker among wild-type FLT3 patients treated with FLT3 inhibitors is envisaged.
  10. Nat Commun. 2021 02 16. 12(1): 1045
      Recurring chromosomal translocation t(10;17)(p15;q21) present in a subset of human acute myeloid leukemia (AML) patients creates an aberrant fusion gene termed ZMYND11-MBTD1 (ZM); however, its function remains undetermined. Here, we show that ZM confers primary murine hematopoietic stem/progenitor cells indefinite self-renewal capability ex vivo and causes AML in vivo. Genomics profilings reveal that ZM directly binds to and maintains high expression of pro-leukemic genes including Hoxa, Meis1, Myb, Myc and Sox4. Mechanistically, ZM recruits the NuA4/Tip60 histone acetyltransferase complex to cis-regulatory elements, sustaining an active chromatin state enriched in histone acetylation and devoid of repressive histone marks. Systematic mutagenesis of ZM demonstrates essential requirements of Tip60 interaction and an H3K36me3-binding PWWP (Pro-Trp-Trp-Pro) domain for oncogenesis. Inhibitor of histone acetylation-'reading' bromodomain proteins, which act downstream of ZM, is efficacious in treating ZM-induced AML. Collectively, this study demonstrates AML-causing effects of ZM, examines its gene-regulatory roles, and reports an attractive mechanism-guided therapeutic strategy.
  11. Cell Rep. 2021 Jan 26. pii: S2211-1247(20)31659-4. [Epub ahead of print]34(4): 108670
      Inflammation-dependent base deaminases promote therapeutic resistance in many malignancies. However, their roles in human pre-leukemia stem cell (pre-LSC) evolution to acute myeloid leukemia stem cells (LSCs) had not been elucidated. Comparative whole-genome and whole-transcriptome sequencing analyses of FACS-purified pre-LSCs from myeloproliferative neoplasm (MPN) patients reveal APOBEC3C upregulation, an increased C-to-T mutational burden, and hematopoietic stem and progenitor cell (HSPC) proliferation during progression, which can be recapitulated by lentiviral APOBEC3C overexpression. In pre-LSCs, inflammatory splice isoform overexpression coincides with APOBEC3C upregulation and ADAR1p150-induced A-to-I RNA hyper-editing. Pre-LSC evolution to LSCs is marked by STAT3 editing, STAT3β isoform switching, elevated phospho-STAT3, and increased ADAR1p150 expression, which can be prevented by JAK2/STAT3 inhibition with ruxolitinib or fedratinib or lentiviral ADAR1 shRNA knockdown. Conversely, lentiviral ADAR1p150 expression enhances pre-LSC replating and STAT3 splice isoform switching. Thus, pre-LSC evolution to LSCs is fueled by primate-specific APOBEC3C-induced pre-LSC proliferation and ADAR1-mediated splicing deregulation.
    Keywords:  Enter keywords here
  12. Leukemia. 2021 Feb 15.
      Precision medicine is gaining importance in the treatment of acute myeloid leukemia (AML). Objectively reviewing past and current knowledge aids guiding future research. Therefore, we provide a complete overview of all phase II and phase III trials investigating targeted therapies in AML and their primary endpoints over the past two decades in perspective of their clinical benefit. We assessed whether drugs were primarily designed to treat AML or were repurposed and how successful they were based on progression of distinct drugs from phase II to phase III to FDA-approval. Between January 2000 and September 2020, 167 agents with 96 targets were investigated in 397 phase II trials. Twenty-eight agents were steered towards phase III, after three phase II trials on average. Repurposed drugs less often advanced in clinical development than drugs primarily developed for AML. Composite responses were the most prevalent primary endpoints in phase II. Of the eight FDA-approved drugs, none investigated quality of life at time of approval, and three out of eight have yet to show benefit in overall survival. Returns on targeted therapy research remain lean for AML patients. Future trials should not overlook non-targeted agents and foremost study endpoints proven to predict patient well-being.
  13. Nat Commun. 2021 02 16. 12(1): 1054
      In acute myeloid leukemia (AML), molecular heterogeneity across patients constitutes a major challenge for prognosis and therapy. AML with NPM1 mutation is a distinct genetic entity in the revised World Health Organization classification. However, differing patterns of co-mutation and response to therapy within this group necessitate further stratification. Here we report two distinct subtypes within NPM1 mutated AML patients, which we label as primitive and committed based on the respective presence or absence of a stem cell signature. Using gene expression (RNA-seq), epigenomic (ATAC-seq) and immunophenotyping (CyToF) analysis, we associate each subtype with specific molecular characteristics, disease differentiation state and patient survival. Using ex vivo drug sensitivity profiling, we show a differential drug response of the subtypes to specific kinase inhibitors, irrespective of the FLT3-ITD status. Differential drug responses of the primitive and committed subtype are validated in an independent AML cohort. Our results highlight heterogeneity among NPM1 mutated AML patient samples based on stemness and suggest that the addition of kinase inhibitors to the treatment of cases with the primitive signature, lacking FLT3-ITD, could have therapeutic benefit.
  14. Blood Adv. 2021 Feb 23. 5(4): 1017-1028
      Hypomethylating agents (HMAs) are widely used in the treatment of myelodysplastic syndromes (MDSs), yet identifying those patients unlikely to benefit remains challenging. We assessed response and overall survival (OS) in 247 patients molecularly profiled by next-generation sequencing (NGS) before first-line HMA therapy, and a subset of 108 patients were sequenced serially during treatment. The most common mutations included TP53 (33.1%), ASXL1 (19%), TET2 (16.5%), DNMT3A (14.1%), and SRSF2 (12.1%). The overall response rate was 42.1%, with the composite TET2-mutant/ASXL1 wild-type genotype representing the strongest predictor of response (overall response rate, 62.1%; complete remission rate, 34.5%). The median OS for the cohort was 15 months, and the number of mutations detected by NGS (hazard ratio [HR], 1.22; P = .02), as well as mutations in TP53 (HR, 2.33; P = .001) and EZH2 (HR, 2.41; P = .04) were identified as independent covariates associated with inferior OS in multivariable analysis. Serial molecular profiling revealed that clearance of TP53 mutations during HMA therapy was associated with superior OS (HR, 0.28; P = .001) and improved outcome in patients proceeding to allogeneic hematopoietic cell transplantation. These data support baseline molecular profiling by NGS in MDS patients treated with HMAs and provide novel observations of sequential profiling during therapy that provide particular value in TP53-mutated disease.
  15. Front Oncol. 2020 ;10 619085
      Recent advances in therapeutics coupled with steady improvements in supportive care for patients with acute myeloid leukemia (AML) have led to improved outcomes. Despite these advances, even in patients that achieve a complete remission with initial therapy high rates of relapse remain a clinical dilemma. For decades, investigators have attempted strategies of maintenance therapy to prolong both remission duration and overall survival in patients with AML. These approaches have included cytotoxic chemotherapy, immunotherapy, hypomethylating agents, and targeted small molecule therapy. Overall, the evidence in favor of maintenance therapy is limited. Recent strategies, especially with hypomethylating agents have begun to show promise as maintenance therapy in improving clinical outcomes. Ongoing and future studies will continue to elucidate the true role for maintenance therapy options in patients with AML. In this review we summarize prior and ongoing maintenance therapy approaches in AML and highlight some of the most promising strategies.
    Keywords:  acute myeloid leukemia; cancer; chemotherapy; immunotherapy; maintenance therapy; targeted therapy
  16. J Clin Oncol. 2021 Feb 18. JCO2002342
      PURPOSE: TP53-mutated (TP53m) myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) have very poor outcome irrespective of the treatment received, including 40% responses (20% complete remission [CR]) with azacitidine (AZA) alone, short response duration, and a median overall survival (OS) of approximately 6 months. Eprenetapopt (APR-246), a novel first-in-class drug, leads to p53 protein reconformation and reactivates its proapoptotic and cell-cycle arrest functions.PATIENTS AND METHODS: This phase II study assessed the safety and efficacy of eprenetapopt in combination with AZA in untreated high or very high International Prognostic Scoring System-R TP53m MDS and AML patients.
    RESULTS: Fifty-two TP53m patients (34 MDS, 18 AML [including seven with more than 30% blasts]) were enrolled. In MDS, we observed an overall response rate (ORR) of 62%, including 47% CR, with a median duration of response at 10.4 months. In AML, the ORR was 33% including 17% CR (27% and 0% CR in AML with less than and more than 30% marrow blasts, respectively). Seventy-three percent of responders achieved TP53 next-generation sequencing negativity (ie, variant allele frequency < 5%). The main treatment-related adverse events were febrile neutropenia (36%) and neurologic adverse events (40%), the latter correlating with a lower glomerular filtration rate at treatment onset (P < .01) and higher age (P = .05), and resolving with temporary drug interruption without recurrence after adequate eprenetapopt dose reduction. With a median follow-up of 9.7 months, median OS was 12.1 months in MDS, and 13.9 and 3.0 months in AML with less than and more than 30% marrow blasts, respectively.
    CONCLUSION: In this very high-risk population of TP53m MDS and AML patients, eprenetapopt combined with AZA was safe and showed potentially higher ORR and CR rate, and longer OS than reported with AZA alone.
  17. Leukemia. 2021 Feb 18.
      Early results of the randomized placebo-controlled SORAML trial showed that, in patients with newly diagnosed acute myeloid leukaemia (AML), sorafenib led to a significant improvement in event-free (EFS) and relapse-free survival (RFS). In order to describe second-line treatments and their implications on overall survival (OS), we performed a study after a median follow-up time of 78 months. Newly diagnosed fit AML patients aged ≤60 years received sorafenib (n = 134) or placebo (n = 133) in addition to standard chemotherapy and as maintenance treatment. The 5-year EFS was 41 versus 27% (HR 0.68; p = 0.011) and 5-year RFS was 53 versus 36% (HR 0.64; p = 0.035). Allogeneic stem cell transplantation (allo SCT) was performed in 88% of the relapsed patients. Four years after salvage allo SCT, the cumulative incidence of relapse was 54 versus 35%, and OS was 32 versus 50%. The 5-year OS from randomization in all study patients was 61 versus 53% (HR 0.82; p = 0.282). In conclusion, the addition of sorafenib to chemotherapy led to a significant prolongation of EFS and RFS. Although the OS benefit did not reach statistical significance, these results confirm the antileukaemic activity of sorafenib.
  18. Cell Rep. 2021 Jan 26. pii: S2211-1247(20)31652-1. [Epub ahead of print]34(4): 108663
      Self-renewal is a key characteristic of leukemia stem cells (LSCs) responsible for the development and maintenance of leukemia. In this study, we identify CD93 as an important regulator of self-renewal and proliferation of murine and human LSCs, but not hematopoietic stem cells (HSCs). The intracellular domain of CD93 promotes gene transcription via the transcriptional regulator SCY1-like pseudokinase 1 independently of ligation of the extracellular domain. In a drug library screen, we identify the anti-emetic agent metoclopramide as an efficient blocker of CD93 signaling. Metoclopramide treatment reduces murine and human LSCs in vitro and prolongs survival of chronic myeloid leukemia (CML) mice through downregulation of pathways related to stemness and proliferation in LSCs. Overall, these results identify CD93 signaling as an LSC-specific regulator of self-renewal and proliferation and a targetable pathway to eliminate LSCs in CML.
    Keywords:  CD93; chronic myeloid leukemia; leukemia stem cells; metoclopramide; self-renewal
  19. Expert Rev Anticancer Ther. 2021 Feb 16.
      INTRODUCTION: Acute myeloid leukemia (AML) is an aggressive blood cancer that proves fatal for the majority of affected individuals. Older patients are particularly vulnerable due to more unfavorable disease biology and diminished ability to tolerate intensive induction chemotherapy (ICT). Safer, more efficacious therapies are desperately needed.AREAS COVERED: We briefly summarize the challenges facing AML treatment and introduce the rapidly-expanding therapeutic landscape. Our focus is on the Hedgehog (Hh) pathway and how preclinical evidence has spurred the clinical development of selective inhibitors for oncology indications. Glasdegib is the first Hh pathway inhibitor approved for the treatment of a hematologic malignancy, and we review its pharmacology, safety, efficacy, and potential clinical impact in AML patients.
    EXPERT OPINION: Advances in the mechanistic understanding of AML have started to translate into improved therapeutic options for patients with contraindications to ICT. Glasdegib improved overall survival in this population when combined with low-dose cytarabine. While an encouraging development for these difficult to treat patients, alternative combination therapy approaches such as venetoclax plus azacitidine have gained greater clinical traction. Further investigation of glasdegib combination strategies and predictive biomarkers, particularly in regard to overcoming chemoresistance and preventing relapse, is needed to better define its clinical utility.
    Keywords:  AML; combination drug therapy; hedgehog proteins; molecular targeted therapy; myelogenous leukemia
  20. Leukemia. 2021 Feb 15.
      We report here on a novel pro-leukemogenic role of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) that interferes with microRNAs (miRNAs) biogenesis in acute myeloid leukemia (AML) blasts. We showed that FLT3-ITD interferes with the canonical biogenesis of intron-hosted miRNAs such as miR-126, by phosphorylating SPRED1 protein and inhibiting the "gatekeeper" Exportin 5 (XPO5)/RAN-GTP complex that regulates the nucleus-to-cytoplasm transport of pre-miRNAs for completion of maturation into mature miRNAs. Of note, despite the blockage of "canonical" miRNA biogenesis, miR-155 remains upregulated in FLT3-ITD+ AML blasts, suggesting activation of alternative mechanisms of miRNA biogenesis that circumvent the XPO5/RAN-GTP blockage. MiR-155, a BIC-155 long noncoding (lnc) RNA-hosted oncogenic miRNA, has previously been implicated in FLT3-ITD+ AML blast hyperproliferation. We showed that FLT3-ITD upregulates miR-155 by inhibiting DDX3X, a protein implicated in the splicing of lncRNAs, via p-AKT. Inhibition of DDX3X increases unspliced BIC-155 that is then shuttled by NXF1 from the nucleus to the cytoplasm, where it is processed into mature miR-155 by cytoplasmic DROSHA, thereby bypassing the XPO5/RAN-GTP blockage via "non-canonical" mechanisms of miRNA biogenesis.
  21. Leuk Lymphoma. 2021 Feb 13. 1-13
      Bromodomain and extra-terminal (BET) proteins can drive carcinogenesis and therapy resistance. RO6870810 (RO) is a novel, small-molecule BET inhibitor. We conducted a study in 32 patients with relapsed/refractory acute myeloid leukemia and hypomethylating agent-refractory myelodysplastic syndrome (NCT02308761). Pharmacodynamic assessments showed decreases in CD11b in peripheral blood mononuclear cells at RO concentrations above 120 ng/mL. Treatment emergent adverse events were generally mild and the most frequent were fatigue, injection site reactions, diarrhea, decreased appetite and nausea. There were no treatment-related deaths. Potential drug-related dose limiting toxicities included decreased appetite, congestive cardiac failure, hypertension, fatigue, increased conjugated bilirubin and increased gamma glutamyltransferase. One AML patient achieved complete remission after withdrawal from study. Eleven AML patients experienced SD. For AML, the median OS was 72.0 days. For MDS, two patients experienced SD. Further development of RO as monotherapy was discontinued due to lack of efficacy, but combinations with other agents are under consideration.
    Keywords:  AML; BET inhibitor; MDS; phase 1
  22. ChemMedChem. 2021 Feb 16.
      Checkpoint kinase 1 (CHK1) is a central component in DNA damage response and has emerged as a target for antitumor therapeutics. Herein, we describe the design, synthesis, and biological evaluation of a novel series of potent diaminopyrimidine CHK1 inhibitors. The compounds exhibited moderate to potent CHK1 inhibition and could suppress the proliferation of malignant hematological cell lines. The optimized compound 13 had a CHK1 IC50 value of 7.73±0.74 nM, and MV-4-11 cells were sensitive to it (IC50 =0.035±0.007 μM). Furthermore, compound 13 was metabolically stable in mouse liver microsomes in vitro and displayed moderate oral bioavailability in vivo. Moreover, treatment of MV-4-11 cells with compound 13 for 2 h led to robust inhibition of CHK1 autophosphorylation on serine 296. Based on these biochemical results, we consider compound 13 to be a promising CHK1 inhibitor and potential anticancer therapeutic agent.
    Keywords:  CHK1 inhibitor; DNA damage response; diaminopyrimidine; oral bioavailability
  23. J Med Chem. 2021 Feb 16.
      Acute myeloid leukemia (AML) is marked by significant unmet clinical need due to both poor survival and high relapse rates where long-term disease control for most patients with relapsed or refractory AML remain dismal. Inspired to bring novel therapeutic options to these patients, we envisioned protein degradation as a potential therapeutic approach for the treatment of AML. Following this course, we discovered and pioneered a novel mechanism of action which culminated in the discovery of CC-90009. CC-90009 represents a novel protein degrader and the first cereblon E3 ligase modulating drug to enter clinical development that specifically targets GSPT1 (G1 to S phase transition 1) for proteasomal degradation. This manuscript briefly summarizes the mechanism of action, scientific rationale, medicinal chemistry, pharmacokinetic properties, and efficacy data for CC-90009, which is currently in phase 1 clinical development.
  24. Blood Adv. 2021 Feb 23. 5(4): 994-1002
      The phase 3 VIALE-A trial reported that venetoclax in combination with azacitidine significantly improved response rates and overall survival compared with azacitidine alone in older, unfit patients with previously untreated acute myeloid leukemia (AML). However, the cost-effectiveness of azacitidine-venetoclax in this clinical setting is unknown. In this study, we constructed a partitioned survival model to compare the cost and effectiveness of azacitidine-venetoclax with azacitidine alone in previously untreated AML. Event-free and overall survival curves for each treatment strategy were derived from the VIALE-A trial using parametric survival modeling. We calculated the incremental cost-effectiveness ratio (ICER) of azacitidine-venetoclax from a US-payer perspective. Azacitidine-venetoclax was associated with an improvement of 0.61 quality-adjusted life-years (QALYs) compared with azacitidine alone. However, the combination led to significantly higher lifetime health care costs (incremental cost, $159 595), resulting in an ICER of $260 343 per QALY gained. The price of venetoclax would need to decrease by 60% for azacitidine-venetoclax to be cost-effective at a willingness-to-pay threshold of $150 000 per QALY. These data suggest that use of azacitidine-venetoclax for previously untreated AML patients who are ineligible for intensive chemotherapy is unlikely to be cost-effective under current pricing. Significant price reduction of venetoclax would be required to reduce the ICER to a more widely acceptable value.
  25. Cancer Discov. 2021 Jan 27. pii: candisc.1227.2020. [Epub ahead of print]
      Mitochondria are involved in many biological processes including cellular homeostasis, energy generation and apoptosis. Moreover, mitochondrial and metabolic pathways are interconnected with gene expression to regulate cellular functions such as cell growth, survival, differentiation and immune recognition. Metabolites and mitochondrial enzymes regulate chromatin modifying-enzymes, chromatin remodeling, and transcription regulators. Deregulation of mitochondrial pathways and metabolism leads to alterations in gene expression that promotes cancer development, progression and evasion of the immune system. This review highlights how mitochondrial and metabolic pathways function as a central mediator to control gene expression, specifically on stem cell functions, differentiation and immune response in leukemia.