Acute Myeloid Leukemia Models Research Articles

Models to study myelodysplastic syndrome and acute myeloid leukaemia.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are hematological malignancies characterized by complex genetic alterations, leading to poor clinical outcomes. Despite advances in treatment, there is an urgent need for novel therapeutic approaches. This review outlines recent progress in humanized models of MDS and AML and highlight their role in advancing our understanding of these diseases. Patient derived xenografts (PDXs) were among the first humanized models for studying MDS and AML, allowing researchers to analyze patient-specific cancer properties in vivo. However, they face challenges related to sample availability and consistent engraftment in mice. New methods, including specialized mouse strains and human tissue scaffolds, have been developed to address these issues. Induced pluripotent stem cells (iPSCs) offer the advantage of indefinite expansion and genetic modification, making them valuable for in vitro research, though protocols to enhance their engraftment in vivo are still being refined. Genetically engineered human primary hematopoietic stem and progenitor cells (HSPCs) provide reliable in vivo models with good engraftment in mice, and recent advancements in culture systems and gene-editing techniques are helping to overcome challenges related to ex vivo expansion and genetic modification. PDXs, iPSCs, and genetically engineered HSPCs are crucial models for the study of MDS and AML. This review discusses strengths, limitations, and recent advancements of these humanized models, which provide insights into human-specific disease biology and therapeutic development.

Dual specific STAT3/5 degraders effectively block acute myeloid leukemia and natural killer/T cell lymphoma.

The transcription factors STAT3, STAT5A, and STAT5B steer hematopoiesis and immunity, but their enhanced expression and activation promote acute myeloid leukemia (AML) or natural killer/T cell lymphoma (NKCL). Current therapeutic strategies focus on blocking upstream tyrosine kinases to inhibit STAT3/5, but these kinase blockers are not selective against STAT3/5 activation and frequent resistance causes relapse, emphasizing the need for targeted drugs. We evaluated the efficacy of JPX-0700 and JPX-0750 as dual STAT3/5 binding inhibitors promoting protein degradation. JPX-0700/-0750 decreased the mRNA and protein levels of STAT3/5 targets involved in cancer survival, metabolism, and cell cycle progression, exhibiting nanomolar to low micromolar efficacy. They induced cell death and growth arrest in both AML/NKCL cell lines and primary AML patient blasts. We found that both AML/NKCL cells hijack STAT3/5 signaling through either upstream activating mutations in kinases, activating mutations in STAT3, mutational loss of negative STAT regulators, or genetic gains in anti-apoptotic, pro-proliferative, or epigenetic-modifying STAT3/5 targets. This emphasizes a vicious cycle for proliferation and survival through STAT3/5. Both JPX-0700/-0750 treatment reduced leukemic cell growth in human AML or NKCL xenograft mouse models significantly, being well tolerated by mice. Synergistic cell death was induced upon combinatorial use with approved chemotherapeutics in AML/NKCL cells.

Autophagy inhibition induces AML cell death and enhances the efficacy of chemotherapy under hypoxia.

Outcomes of relapsed/refractory acute myeloid leukemia (AML) are poor, and strategies to improve outcomes are urgently needed. One important factor promoting relapse and chemoresistance is the ability of AML cells to thrive in vivo within an intrinsically hypoxic bone marrow microenvironment. Here we show that human AML cells exhibit enhanced autophagy, specifically mitophagy (i.e., increased accumulation of mitochondria and decreased mitochondrial membrane potential) under hypoxia. To target this pathway, we investigated the activity of the potent chloroquine-derived autophagy inhibitor, Lys05, on human AML cells, patient samples, and patient derived xenograft models. Inhibition of autophagy by Lys05 in AML cells prevented removal of damaged mitochondria and preferentially enhanced cell death under hypoxia mirroring the marrow microenvironment. Lys05 eradicated human AML cells of all genotypes including p53 mutant cells. Lys05 treatment in primary AML xenografted mice decreased CD34+CD38- human cells and prolonged overall survival. Moreover, Lys05 overcame hypoxia-induced chemoresistance and improved the efficacy of cytarabine, venetoclax, and azacytidine in vitro and in vivo in AML models. Our results demonstrate the importance of autophagy, specifically mitophagy, as a critical survival and chemoresistance mechanism of AML cells under hypoxic marrow conditions. Therapeutic targeting of this pathway in future clinical studies for AML is warranted.

Preclinical activity of resazurin in acute myeloid leukaemia.

Resazurin, a phenoxazine used in cell viability assays, acts invitro as an anti-leukaemic compound through the production of cellular reactive oxygen species (ROS) resulting in mitochondrial dysfunction and cell death. However, the invivo tolerance and efficacy of resazurin in cancer are unknown. In this study, we investigated the invitro and invivo effects of resazurin in acute myeloid leukaemia (AML). Resazurininduced cell death in a dose-dependent manner in AML cell lines and reduced proliferation and colony formation in exvivo treated patient-derived AML cells. Cells treated with a reduced dose of resazurin for 72 h acquired a more mature immunophenotype suggesting cell differentiation as a mechanism contributing to the anti-leukaemic effect. Invivo optical imaging in healthy mice demonstrated a reduction of resazurin to resorufin within 30 min and non-detectable after 2 h, supporting dosing twice daily as optimal. In subcutaneous and orthotopic models of MV4-11 AML in NOD/SCID IL2rγnull mice, anti-tumour effects and an increased survival were found at a dose level of 75 mg/kg twice daily without observed toxicity. Our results suggest that resazurin represents a novel experimental therapeutic for the treatment of AML.

IL-21/IL-21R signaling renders acute myeloid leukemia stem cells more susceptible to cytarabine treatment and CAR T cell therapy

Self-renewal programs in leukemia stem cells (LSCs) predict poor prognosis in patients with acute myeloid leukemia (AML). We identify CD4+ Tcell-derived interleukin (IL)-21 as an important negative regulator of self-renewal of LSCs. IL-21/IL-21R signaling favors asymmetric cell division and differentiation in LSCs through the activation of p38-MAPK signaling, resulting in reduced LSC numbers and significantly prolonged survival in murine AML models. In human AML, serum IL-21 at diagnosis is identified as an independent positive prognostic biomarker for outcome and correlates with improved survival and higher complete remission rates in patients that underwent high-dose chemotherapy. IL-21 treatment inhibits primary LSC function and enhances the effect of cytarabine and CD70 CAR Tcell treatment on LSCs invitro. Low-dose IL-21 treatment prolongs the survival of AML mice in syngeneic and xenograft experiments. Therefore, promoting IL-21/IL-21R signaling on LSCs may be an approach to reduce stemness and increase differentiation in AML.

Investigating the biology of microRNA links to ALDH1A1 reveals candidates for preclinical testing in acute myeloid leukemia.

Aldehyde dehydrogenase 1 family member A1 (ALDH1A1) is a member of the aldehyde dehydrogenase gene subfamily that encode enzymes with the ability to oxidize retinaldehyde. It was recently shown that high ALDH1A1 RNA abundance correlates with a poor prognosis in acute myeloid leukemia (AML). AML is a hematopoietic malignancy associated with high morbidity and mortality rates. Although there are a number of agents that inhibit ALDH activity, it would be crucial to develop methodologies for adjustable genetic interference, which would permit interventions on several oncogenic pathways in parallel. Intervention in multiple oncogenic pathways is theoretically possible with microRNAs (miRNAs or miRs), a class of small non‑coding RNAs that have emerged as key regulators of gene expression in AML. A number of miRNAs have shown the ability to interfere with ALDH1A1 gene expression directly in solid tumor cells, and these miRNAs can be evaluated in AML model systems. There are indications that a few of these miRNAs actually do have an association with AML disease course, rendering them a promising target for genetic intervention in AML cells.

Gallic acid enhances GVL effects of T cells without exacerbating GVHD after haematopoietic stem cell transplantation.

Allogeneic haematopoietic stem cell transplantation (allo-HSCT) is an effective therapy for acute myeloid leukaemia (AML), predominantly due to its potent graft-versus-leukaemia (GVL) effect. However, leukaemia relapse remains a major obstacle to the success of allo-HSCT. In this study, we demonstrated that gallic acid (GA), a natural dietary compound, can enhance T-cell-mediated GVL effects both invitro and invivo. GA-treated T cells exhibited increased activation and elevated secretion of cytotoxic cytokines, leading to the apoptosis of AML cells in co-culture systems invitro. In a non-irradiated leukaemia mouse model, we showed that GA treatment prolonged the survival of leukaemic mice and reduced leukaemia cell infiltration. Further analysis revealed that GA treatment increased T-cell activation and tumour necrosis factor-α secretion. Moreover, integrated transcriptomic and proteomic analyses indicated that GA augments T-cell-mediated GVL effects through the activation of the MAPK and NF-κB pathways. Blocking these pathways individually diminished the protective effect of GA in AML model mice. Importantly, GA administration did not accelerate graft-versus-host disease (GVHD) progression in a mouse model. In conclusion, our study revealed that GA can enhance the GVL effects of T cells without exacerbating GVHD, offering insights into its potential to improve outcomes for patients after HSCT.

A phase 1 study of the amino acid modulator pegcrisantaspase and venetoclax for relapsed or refractory acute myeloid leukemia

AbstractGlutamine dependency has been shown to be a metabolic vulnerability in acute myeloid leukemia (AML). Prior studies using several in vivo AML models showed that depletion of plasma glutamine, induced by long-acting crisantaspase (pegcrisantaspase [PegC]) was synergistic with the BCL-2 inhibitor venetoclax (Ven), resulting in significantly reduced leukemia burden and enhanced survival. Here, we report a phase 1 study of the combination of Ven and PegC (VenPegC) for treating adult patients with relapsed or refractory AML, including patients who had previously received Ven. The primary end points were the incidence of regimen-limiting toxicities (RLTs) and the maximum tolerated dose (MTD). Twenty-five patients received at least 1 PegC dose with Ven, and 18 efficacy-evaluable patients completed at least 1 VenPegC cycle; 12 (67%) had previously received Ven. Hyperbilirubinemia was the RLT and occurred in 60% of patients treated with VenPegC; 20% had grade ≥3 bilirubin elevations. MTD was determined to be Ven 400 mg daily with biweekly PegC 750 IU/m2. The most common treatment-related adverse events of any grade in 25 patients who received VenPegC included antithrombin III decrease (52%), elevated transaminases (36%-48%), fatigue (28%), and hypofibrinogenemia (24%). No thromboembolic or hemorrhagic adverse events or clinical pancreatitis were observed. The overall complete remission rate in efficacy-evaluable patients was 33%. Response correlated with alterations in proteins involved in messenger RNA translation. In patients with RUNX1 mutations, the composite complete rate was 100%. This study was registered at www.ClinicalTrials.gov as #NCT04666649.

Targeting epigenetic regulation and post-translational modification with 5-Aza-2’ deoxycytidine and SUMO E1 inhibition augments T-cell receptor therapy

BackgroundCellular immunotherapy using modified T cells offers new avenues for cancer treatment. T-cell receptor (TCR) engineering of CD8 T cells enables these cells to recognize tumor-associated antigens and tumor-specific neoantigens....

A novel bispecific T-cell engager using the ligand-target csGRP78 against acute myeloid leukemia

Current medical therapies for treating acute myeloid leukemia (AML) remain unmet, and AML patients may benefit from targeted immunotherapy approaches that focus on specific tumor antigens. GRP78, which is upregulated in various malignant tumors such as AML, is partially expressed as cell surface GRP78 (csGRP78) on the cell membrane, making it an ideal target for redirecting T cells, including T-cell engagers. However, considering the conventional approach of using two scFv segments to construct a bispecific T-cell engager (BiTE), we have undertaken the development of a novel BiTE that utilizes a cyclic peptide ligand to specifically target csGRP78, which we refer to as GRP78-CD3/BiTE. We studied the effects of GRP78-CD3/BiTE on treatments for AML in vitro and in vivo and assessed the pharmacokinetics of this engager. Our findings demonstrated that GRP78-CD3/BiTE could not only effectively mediate the cytotoxicity of T cells against csGRP78-expressing AML cells but also specifically eliminate primary AML tumor cells in vitro. Furthermore, GRP78-CD3/BiTE exhibited a longer half-life despite having a lower molecular weight than CD19-CD3/BiTE. In a xenograft mouse model of AML, treatment with GRP78-CD3/BiTE prolonged the survival time of the mice. Our findings demonstrate that GRP78-CD3/BiTE is effective and selective for eliminating csGRP78-expressing AML cells and suggest that this approach to targeted immunotherapy could lead to effective new treatments for AML.

The pro-differentiating capability of a flavonoid-rich extract of Citrus bergamia juice prompts autophagic death in THP-1 cells

Acute myeloid leukemia (AML) is a hematologic neoplasm, characterized by a blockage of differentiation and an unconstrained proliferation of immature myeloid cells. Recently, the survival of leukemia patients has increased thanks to the use of differentiating agents, though these may cause serious side effects. Hence, the search for safer differentiating compounds is necessary. Our aim was to assess the pro-differentiating effects of a flavonoid-rich extract of bergamot juice (BJe) in human monocytic leukemia THP-1 cells, an in vitro AML model. For the first time, we showed that treatment with BJe induced differentiation of THP-1 cells, changes in cell morphology and increased expression of differentiation-associated surface antigens CD68, CD11b and CD14. Moreover, BJe enhanced protein levels of autophagy-associated markers, such as Beclin-1 and LC3, as well as induced the phosphorylation of the MAPKs JNK, ERK and p38, hence suggesting a potential mechanism underlying its antiproliferative effects. Indeed, parallel experiments highlighted that BJe was able to hamper THP-1 cell growth. In conclusion, our study suggests that BJe induces the differentiation of THP-1 cells and reduces their proliferation, highlighting its potential in differentiation therapy of AML.

Stearoyl-CoA desaturase inhibition is toxic to acute myeloid leukemia displaying high levels of the de novo fatty acid biosynthesis and desaturation

Identification of specific and therapeutically actionable vulnerabilities, ideally present across multiple mutational backgrounds, is needed to improve acute myeloid leukemia (AML) patients’ outcomes. We identify stearoyl-CoA desaturase (SCD), the key enzyme in fatty acid (FA) desaturation, as prognostic of patients' outcomes and, using the clinical-grade inhibitor SSI-4, show that SCD inhibition (SCDi) is a therapeutic vulnerability across multiple AML models in vitro and in vivo. Multiomic analysis demonstrates that SCDi causes lipotoxicity, which induces AML cell death via pleiotropic effects. Sensitivity to SCDi correlates with AML dependency on FA desaturation regardless of mutational profile and is modulated by FA biosynthesis activity. Finally, we show that lipotoxicity increases chemotherapy-induced DNA damage and standard chemotherapy further sensitizes AML cells to SCDi. Our work supports developing FA desaturase inhibitors in AML while stressing the importance of identifying predictive biomarkers of response and biologically validated combination therapies to realize their full therapeutic potential.

Epigenetic regulation of noncanonical menin targets modulates menin inhibitor response in acute myeloid leukemia

AbstractMenin inhibitors that disrupt the menin-MLL interaction hold promise for treating specific acute myeloid leukemia (AML) subtypes, including those with KMT2A rearrangements (KMT2A-r), yet resistance remains a challenge. Here, through systematic chromatin-focused CRISPR screens, along with genetic, epigenetic, and pharmacologic studies in a variety of human and mouse KMT2A-r AML models, we uncovered a potential resistance mechanism independent of canonical menin-MLL targets. We show that a group of noncanonical menin targets, which are bivalently cooccupied by active menin and repressive H2AK119ub marks, are typically downregulated after menin inhibition. Loss of polycomb repressive complex 1.1 (PRC1.1) subunits, such as polycomb group ring finger 1 (PCGF1) or BCL6 corepressor (BCOR), leads to menin inhibitor resistance by epigenetic reactivation of these noncanonical targets, including MYC. Genetic and pharmacological inhibition of MYC can resensitize PRC1.1-deficient leukemia cells to menin inhibition. Moreover, we demonstrate that leukemia cells with the loss of PRC1.1 subunits exhibit reduced monocytic gene signatures and are susceptible to BCL2 inhibition, and that combinational treatment with venetoclax overcomes the resistance to menin inhibition in PRC1.1-deficient leukemia cells. These findings highlight the important roles of PRC1.1 and its regulated noncanonical menin targets in modulating the menin inhibitor response and provide potential strategies to treat leukemia with compromised PRC1.1 function.

The E3 ubiquitin ligase Herc1 modulates the response to nucleoside analogs in acute myeloid leukemia

AbstractFor several decades, induction therapy with nucleoside analogs, in particular cytarabine (Ara-C) and, to a lesser extent, fludarabine, has been the standard of care for patients diagnosed with acute myeloid leukemia (AML). However, the antitumor efficacy of nucleoside analogs is often limited by intrinsic and acquired drug resistance, thereby leading to poor therapeutic response and suboptimal clinical outcomes. In this study, we used genome-wide CRISPR-based pharmacogenomic screening to map the genetic factors that modulate the response to nucleoside analogs in AML and identified the E3 ubiquitin ligase, Herc1, as a key modulator of Ara-C response in mouse AML models driven by the KMT2A/MLLT3 fusion or by the constitutive coexpression of Hoxa9 and Meis1, both in vitro and in vivo. Loss of HERC1 enhanced nucleoside analog–induced cell death in both murine and human AML cell lines by compromising cell cycle progression. In-depth proteomic analysis and subsequent validation identified deoxycytidine kinase as a novel target of Herc1 in both mouse AML models. We observed that HERC1 is overexpressed in AML when compared with other cancer types and that higher HERC1 expression was associated with shorter overall survival in patients with AML in the The Cancer Gene Atlas program (TCGA) and BEAT-AML cohorts. Collectively, this study highlights the importance of HERC1 in the response of AML cells to nucleoside analogs, thereby establishing this E3 ubiquitin ligase as a novel predictive biomarker and potential therapeutic target for the treatment of AML.

Targeting ferritinophagy impairs quiescent cancer stem cells in acute myeloid leukemia in vitro and in vivo models.

Acute myeloid leukemia (AML) remains a challenging hematological malignancy with poor prognosis and limited treatment options. Leukemic stem cells (LSCs) contribute to therapeutic failure, relapse, and adverse outcome. This study investigates the role of quiescence and related molecular mechanisms in AML pathogenesis and LSC functions to identify potential therapeutic targets. Transcriptomic analysis revealed that the LSC-enriched quiescent cell population has a distinct gene signature with prognostic relevance in patients with AML. Mechanistically, quiescent blasts exhibit increased autophagic activity, which contributes to their sustained viability. Proteomic profiling uncovered differential requirements for iron metabolism between quiescent and cycling cells, revealing a unique dependence of quiescent cells on ferritinophagy, a selective form of autophagy mediated by nuclear receptor coactivator 4 (NCOA4), which regulates iron bioavailability. We evaluated the therapeutic potential of inhibiting NCOA4-mediated ferritinophagy using genetic knockdown and chemical inhibition approaches. In vitro assays showed that suppression of NCOA4 was toxic to leukemic blasts, particularly the CD34+CD38- LSC-enriched population, without affecting normal CD34+ hematopoietic progenitors. In vivo studies using murine patient-derived xenograft (PDX) models of AML confirmed that NCOA4 inhibition reduced tumor burden and impaired LSC viability and self-renewal, indicating a specific vulnerability of these cells to ferritinophagy disruption. Our findings underscore the role of NCOA4-mediated ferritinophagy in maintaining LSC quiescence and function and suggest that targeting this pathway may be an effective therapeutic strategy for AML. This study highlights the potential of NCOA4 inhibition to improve AML outcomes and paves the way for future research and clinical development.

Development of Epigenetic Modifiers with Therapeutic Potential in FMS-Related Tyrosine Kinase 3/Internal Tandem Duplication (FLT3/ITD) Acute Myeloid Leukemia and Other Blood Malignancies.

Blood cancers encompass a group of diseases affecting the blood, bone marrow, or lymphatic system, representing the fourth most commonly diagnosed cancer worldwide. Leukemias are characterized by the dysregulated proliferation of myeloid and lymphoid cells with different rates of progression (acute or chronic). Among the chronic forms, hairy cell leukemia (HCL) is a rare disease, and no drugs have been approved to date. However, acute myeloid leukemia (AML) is one of the most aggressive malignancies, with a low survival rate, especially in cases with FLT3-ITD mutations. Epigenetic modifications have emerged as promising strategies for the treatment of blood cancers. Epigenetic modulators, such as histone deacetylase (HDAC) inhibitors, are increasingly used for targeted cancer therapy. New hydroxamic acid derivatives, preferentially inhibiting HDAC6 (5a-q), were developed and their efficacy was investigated in different blood cancers, including multiple myeloma (MM), HCL, and AML, pointing out their pro-apoptotic effect as the mechanism of cell death. Among the inhibitors described, 5c, 5g, and 5h were able to rescue the hematopoietic phenotype in vivo using the FLT3-ITD zebrafish model of AML. 5c (leuxinostat) proved its efficacy in cells from FLT3-ITD AML patients, promoting marked acetylation of α-tubulin compared to histone H3, thereby confirming HDAC6 as a preferential target for this new class of hydroxamic acid derivatives at the tested doses.

Preclinical efficacy of the potent, selective menin-KMT2A inhibitor JNJ-75276617 (bleximenib) in KMT2A- and NPM1-altered leukemias

AbstractThe interaction between menin and histone-lysine N-methyltransferase 2A (KMT2A) is a critical dependency for KMT2A- or nucleophosmin 1 (NPM1)–altered leukemias and an emerging opportunity for therapeutic development. JNJ-75276617 (bleximenib) is a novel, orally bioavailable, potent, and selective protein-protein interaction inhibitor of the binding between menin and KMT2A. In KMT2A-rearranged (KMT2A-r) and NPM1-mutant (NPM1c) acute myeloid leukemia (AML) cells, JNJ-75276617 inhibited the association of the menin-KMT2A complex with chromatin at target gene promoters, resulting in reduced expression of several menin-KMT2A target genes, including MEIS1 and FLT3. JNJ-75276617 displayed potent antiproliferative activity across several AML and acute lymphoblastic leukemia (ALL) cell lines and patient samples harboring KMT2A or NPM1 alterations in vitro. In xenograft models of AML and ALL, JNJ-75276617 reduced leukemic burden and provided a significant dose-dependent survival benefit accompanied by expression changes of menin-KMT2A target genes. JNJ-75276617 demonstrated synergistic effects with gilteritinib in vitro in AML cells harboring KMT2A-r. JNJ-75276617 further exhibited synergistic effects with venetoclax and azacitidine in AML cells bearing KMT2A-r in vitro, and significantly increased survival in mice. Interestingly, JNJ-75276617 showed potent antiproliferative activity in cell lines engineered with recently discovered mutations (MEN1M327I or MEN1T349M) that developed in patients refractory to the menin-KMT2A inhibitor revumenib. A cocrystal structure of menin in complex with JNJ-75276617 indicates a unique binding mode distinct from other menin-KMT2A inhibitors, including revumenib. JNJ-75276617 is being clinically investigated for acute leukemias harboring KMT2A or NPM1 alterations, as a monotherapy for relapsed/refractory acute leukemia (NCT04811560), or in combination with AML-directed therapies (NCT05453903).

IL-33-dependent NF-κB activation inhibits apoptosis and drives chemoresistance in acute myeloid leukemia

BackgroundDespite recent advances in therapeutic regimens, the prognosis of acute myeloid leukemia (AML) remains poor. Following our previous finding that interleukin-33 (IL-33) promotes cell survival along with activated NF-κB in AML, we further investigated the role of NF-κB during leukemia development. MethodsFlow cytometry was performed to value the apoptosis and proliferation. qRT-PCR and western blot were performed to detect the expression of IL-6, active caspase 3, BIRC2, Bcl-2, and Bax, as well as activated NF-κB p65 and AKT. Finally, xenograft mouse models and AML patient samples were used to verify the findings observed in AML cell lines. ResultsIL-33-mediated NF-κB activation in AML cell lines contributes to a reduction in apoptosis, an increase in proliferation rate as well as a decrease in drug sensitivity, which were reversed by NF-κB inhibitor, Bay-117085. Moreover, IL-33 decreased the expression of active caspase-3 while increasing the levels of BIRC2, Bcl-2, and Bax, and these effects were blocked by Bay-117085. Additionally, NF-κB activation induced by IL-33 increases the production of IL-6 and autocrine activation of AKT. Co-culture of bone marrow stroma with AML cells resulted in increased IL-33 expression by leukemia cells, along with decreased apoptosis level and reduced drug sensitivity. Finally, we confirmed the in vivo pro-tumor effect mediated by IL-33/ NF-κB axis using a xenograft model of AML. ConclusionOur data indicate that IL-33/IL1RL1-dependent signaling contributes to AML cell activation of NF-κB, which in turn causes autocrine IL-6-induced activation of pAKT, supporting IL-33/NF-κB/pAKT as a potential target for AML therapy.

Synergistic effects of RPT1G, a first-in-class small molecule NAMPT inhibitor, with venetoclax and olaparib in hematological malignancies.

e18512 Background: MultipleBCL-2 and PARP inhibitors are currently in clinical trials, or have been approved for use, in hematological malignancies and solid tumors. Venetoclax, an inhibitor of the apoptosis regulator B-cell lymphoma-2 (BCL-2), has activity in patients with chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). PARP inhibitors, such as Olaparib, exploit synthetic lethality in homologous recombination-deficient tumors, notably in breast and ovarian cancers. However, patients treated with BCL-2 or PARP inhibitors often face relapse and refractory disease, requiring alternative strategies to counter adaptive responses. Nicotinamide Phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the nicotinamide adenine dinucleotide (NAD+) salvage pathway, is upregulated in malignancies and plays a key role in cancer metabolism (e.g., Warburg effect). NAMPT makes nicotinamide mononucleotide which is then converted to NAD+, while PARP enzymes consume NAD+, placing NAMPT directly upstream of PARP. NAMPT overexpression is associated with Venetoclax resistance in leukemia patients, highlighting the link between NAD+, mitochondrial metabolism, and BCL-2 inhibition. Consequently, NAMPT inhibition may synergize with BCL-2 or PARP inhibitors, potentially enhancing 1st-line of treatment outcomes and re-sensitizing refractory cancer cells to BCL-2 or PARP inhibition. Methods: In this study, we investigated the combination effects of Venetoclax and Olaparib with RPT1G, a novel hyperbolic NAMPT inhibitor that simultaneously inhibits and stabilizes NAMPT in a catalytically active state. RPT1G disrupts NAMPT activity without ever turning it off completely avoiding the severe on-target toxicities seen with complete NAMPT inhibitors. Several cell lines, including OCI-AML3 and MV4;11 (AML), RS4;11 (ALL), and RL (diffuse large B-cell lymphoma) were treated with RPT1G and either Venetoclax or Olaparib to determine the degree of drug interactions. In a follow up in vivo study, we treated mice in a human xenograft model using semi-resistant MV4;11 cells with RPT1G alone or in combination with Venetoclax to measure the ability of RPT1G to enhance the effects of Venetoclax. Results: RPT1G achieves significant single-agent efficacy in leukemia and lymphoma mouse xenograft models. When RTP1G is used in combination with either Venetoclax or Olaparib significant synergy is seen across a broad range of concentrations in vitro. Consistent with in vitro synergy results, in a xenograft model of human AML, mice treated with a combination of RPT1G and Venetoclax show enhanced efficacy as compared to Venetoclax alone. Conclusions: Combination of RPT1G with either Venetoclax or Olaparib synergistically enhances killing of leukemic cells and presents as an effective strategy to improve treatment outcomes for patients with diverse malignancies.

A first-in-human phase 1, multicenter, open-label study of CB-012, a next-generation CRISPR-edited allogeneic anti-CLL-1 CAR-T cell therapy for adults with relapsed/refractory acute myeloid leukemia (AMpLify).

TPS6586 Background: CAR-T cell therapies have shown significant clinical benefit in treating adults with many hematologic malignancies. In acute myeloid leukemia (AML), a challenge in the development of CAR-T cell therapies has been the limitation of suitable target antigens since many are also expressed on hematopoietic stem cells (HSCs). The target antigen C-type lectin-like molecule-1 (CLL-1) has emerged as an attractive therapeutic target due to its expression on AML mature blasts and leukemic stem cells and its absence on HSCs. CB-012 is an allogeneic CAR-T cell therapy that targets CLL-1. CB-012 is derived from healthy donor T cells by using Cas12a CRISPR hybrid RNA-DNA (chRDNA) technology to introduce 5 genome edits: (1) TRAC gene knockout (KO), which eliminates T cell receptor expression to reduce the risk of graft-versus-host disease, (2) site-directed insertion of a fully human anti-CLL-1 CAR into the TRAC locus, (3) KO of PD-1 to enhance antitumor activity by reducing T cell exhaustion, (4) β2-microgobulin ( B 2M) gene KO, which eliminates HLA class I presentation to mitigate host T cell-mediated rejection, and (5) site-directed insertion of a B2M–HLA-E-peptide fusion into the B 2M locus to reduce NK cell-mediated rejection. In murine xenograft models of AML, CB-012 significantly reduced the tumor burden and increased the survival of mice bearing CLL-1+PD-L1+ tumors. Methods: CB-012 is being evaluated in a multicenter, Phase 1 clinical trial in patients with relapsed/refractory (r/r) AML. A 3+3 dose escalation design is being utilized with the primary objectives to determine the safety and tolerability of CB-012 and the recommended Phase 2 dose (RP2D). An expansion phase will follow dose escalation at the recommended dose(s) for expansion. Additional objectives include preliminary antitumor activity and pharmacokinetics. Key inclusion criteria include nonproliferative disease defined as ≤25% blasts in the bone marrow and peripheral blood, ECOG performance status ≤1, and adequate organ function. After receiving lymphodepletion therapy with cyclophosphamide (750 mg/m2/d) and fludarabine (30 mg/m2/d) administered concurrently for 3 days followed by a 2-day break, patients receive a single-dose infusion of CB-012 and are followed for safety and efficacy. The dose escalation portion of the study is actively enrolling patients. The AMpLify trial is registered at clinicaltrials.gov (NCT06128044). Clinical trial information: NCT06128044 .