Relapsed Acute Myeloid Leukemia Patients Research Articles

Abstract 7123: Biomarker-targeted alkylator and DNA damage repair inhibitor combination for refractory and relapsed acute myeloid leukemia (AML)

Abstract Isocitrate dehydrogenase 1 and 2 (IDH1/2) convert isocitrate to α-ketoglutarate in the tricarboxylic acid (TCA) cycle. A missense mutation in IDH1/2 leads to accelerated conversion of α-ketoglutarate into 2-hydroxyglutarate (2-HG), an oncometabolite that competitively inhibits α-ketoglutarate-dependent dioxygenases including Ten-Eleven Translocation (TET) enzymes. TET enzymes are DNA demethylases that convert 5-methylcytosine to 5-carboxycytosine and regulate CpG island promoter methylation signatures. In IDH1/2 mutant glioma, inhibition of TET2 enzyme by 2-HG can lead to promoter hypermethylation of O6-methylguanine methyltransferase (MGMT) and reduce its expression. Approximately 10-15% of de novo or treatment-related AML harbor mutually exclusive mutations in IDH1/2 or TET2, and emerging resistance towards clinical IDH1/2 inhibitors, therefore warrants novel therapeutic options. We performed a pan-cancer TCGA analysis and observed MGMT promoter hypermethylation and reduced expression in IDH1/2 AML. Our independent study on 10 AML patients (5 IDH1/2 and 5 TET2 mutant) corroborated the TCGA data and showed a significantly reduced expression of MGMT in comparison to 7 wild-type AML samples. As MGMT resolves O6-alkylguanine lesions during DNA damage, we performed an exhaustive alkylator screen, where temozolomide (TMZ) and our novel compound KL-50 emerged as the top hits that imparted a maximum therapeutic index in multiple MGMT (MGMT+/–) isogenic AML cell line models. Both TMZ and KL-50 induced MGMT-dependent DNA strand breaks and replication stress and activated ATM and ATR DNA damage response pathways in a time-dependent manner. Inhibition of ATR activation with Ceralasertib, an ATR inhibitor (ATRi) currently in clinical trials for chronic myelomonocytic leukemia and myelodysplastic syndromes, imparted a profound MGMT-dependent synergy with TMZ and KL-50. Researchers have established in glioma that mismatch repair (MMR) loss confers resistance to TMZ, and reported studies also show evidence of MMR loss in refractory or relapsed AML patients. Thus, we developed numerous MMR-deficient isogenic AML cell lines in an MGMT+/– background and observed MMR loss-mediated resistance to TMZ and abrogation of its synergy with ATRi. Unlike TMZ, KL-50 retained a profound synergy with ATRi in an MGMT-dependent manner irrespective of MMR status. We are currently investigating our novel KL-50 and ATRi combination in MGMT/MMR isogenic cell line-based in vivo AML models and in AML patient-derived xenografts to establish it as a promising novel biomarker-targeted therapy for AML patients. Citation Format: Prateek Bhardwaj, Ranjini Sundaram, Amro Baassiri, Martin Matthews, Jennifer VanOudenhove, Susan Gueble, Stephanie Halene, Ranjit Bindra. Biomarker-targeted alkylator and DNA damage repair inhibitor combination for refractory and relapsed acute myeloid leukemia (AML) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7123.

Abstract P03: Splicing factor mutations induce stress granule upregulation in myeloid malignancies

Abstract Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are aggressive blood cancers with a 5-year relative survival rate of only 37% and 28%, respectively [Sekeres MA, Taylor J. JAMA. 2022; https://www.cancer.net/cancer-types/leukemia-acute-myeloid-aml/statistics]. This highlights the need to better characterize the crucial oncogenic mechanisms sustaining cancer stem cell fitness in order to develop more effective therapies. Somatic mutations affecting splicing factor genes represent a hallmark of myeloid blood cancers [Saez B, et al. Blood. 2017]. Splicing factor mutations alter the splicing process of thousands of RNA molecules, but how they provide clonal advantage with consequent ineffective hematopoiesis remains an unanswered question. We integrated fractionated enhanced UV-crosslinking and immunoprecipitation (freCLIP-seq), bulk RNA-seq and immunofluorescence imaging demonstrating that U2AF1 mutations in myeloid malignancies alter the biology of stress granules (SGs), whose upregulation has been linked to tumorigenesis [Redding A, Grabocka E. Trends Cancer. 2023]. U2AF1 mutations, through RNA binding and splicing alterations, increase the availability of SG components leading to enhanced stress adaptation. Crucially, U2AF1-mutant cells show improved cell fitness that can be reverted by a SG inhibitor [Biancon G, et al. Mol Cell. 2022]. These observations have been recently validated at single-cell level in MDS patients (n=10) without splicing factor mutations, with U2AF1 S34F mutation, or with SRSF2 P95H mutation that carries an equally poor prognosis as U2AF1-mutant disease. We isolated CD34+ blasts from bone marrow samples and performed 10x Genomics 5' scRNA-seq. Integrating cell type annotation (https://github.com/TebaldiLab/TheCellMarkerAccordion) with mutational analysis (VarTrix v1.1.19), we clearly distinguished an enrichment of U2AF1 mutant cells and of SRSF2 mutant cells in hematopoietic multipotent progenitor cells. The enrichment is observed also in monocytic cells that are also characterized by high SG score. Of note, it has been recently showed that leukemic stem cells with monocytic phenotype are associated to relapse in AML patients treated with BCL2-inh [Pei S, et al. Cancer Discov. 2023]. We then identified the top influential SG genes in each annotated mutant population and conducted functional enrichment analysis. In hematopoietic multipotent progenitor cells, the biological processes mainly affected by the SG upregulation are regulation of translation, of microtubule, of transcription and of cell growth. Changes in SGs may represent the collective result of splicing aberrancies that drive ineffective hematopoiesis in MDS and AML, or other potential tumorigenic phenotypes. Splicing factor mutations are in fact reported in several cancer types [Stanley RF, Abdel-Wahab O. Nat Cancer. 2022] and SGs are involved in several cancer hallmarks [Boija A, et al. Cancer Cell. 2021]. Alterations in SGs provide therefore novel therapeutic opportunities in blood cancers and potentially in other cancers. Citation Format: Giulia Biancon, Emma Busarello, Matthew Cheng, Domitilla Baccon, Jennifer VanOudenhove, Fabio Ciceri, Toma Tebaldi, Stephanie Halene. Splicing factor mutations induce stress granule upregulation in myeloid malignancies [abstract]. In: Proceedings of the Blood Cancer Discovery Symposium; 2024 Mar 4-6; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(2_Suppl):Abstract nr P03.

Increased expression of CD70 in relapsed acute myeloid leukemia after hypomethylating agents.

Acute myeloid leukemia (AML) is the most common acute leukemia in adults. While induction chemotherapy leads to remission in most patients, a significant number will experience relapse. Therefore, there is a need for novel therapies that can improve remission rates in patients with relapsed and refractory AML. CD70 is the natural ligand for CD27 (a member of the TNF superfamily) and appears to be a promising therapeutic target. Consequently, there is considerable interest in developing chimeric antigen receptor (CAR) T-cell therapy products that can specifically target CD70 in various neoplasms, including AML. In this study, we employed routine diagnostic techniques, such as immunohistochemistry and flow cytometry, to investigate the expression of CD70 in bone marrow samples from treatment-naïve and relapsed AML patients after hypomethylating agents (HMA). Also, we evaluated the impact of HMA on CD70 expression and examined CD70 expression in various leukemic cell subsets and normal hematopoietic progenitors.

CD74 + Leukemia-Associated Macrophages Supporess T Cell Immune Surveillance and Promote Leukemic Cell Growth in Acute Myeloid Leukemia

The bone marrow microenvironment plays a pivotal role in the recurrence of acute myeloid leukemia (AML). However, the exact mechanisms are not fully understood. Single-cell technologies have emerged as powerful tools for unraveling the immune microenvironment in leukemia. In this study, utilizing scRNA-seq on a cohort of 13 paired AML patients, we have unveiled a distinctive subcluster of tumor-associated macrophages (TAMs) linked to relapse leukemia. To explore the heterogeneity of the bone marrow microenvironment during the progression of AML, we conducted a scRNA-seq analysis on bone marrow cells obtained from 13 paired AML patients at the time of diagnosis (DX) and relapse (RE) (Figure 1A). Employing UMAP for dimensionality reduction, we detected multiple subclusters and observed a notable rise in the Macrophage CD74 cluster in all paired RE patients, suggesting a pivotal role of CD74+ TAMs in AML relapse (Figure 1B-C). Furthermore, CD274, FOS, TGFβ1, and CD163, recognized as markers of M2 macrophages, were significantly enriched in the CD74+ TAMs population (Figure 1D). Intriguingly, a higher proportion of CD74+ TAMs correlated with unfavorable outcomes in TCGA database (Figure 1E). Meanwhile, we found that the ligand macrophage migration inhibitory factor (MIF) of CD74 was associated with poor prognosis of AML (Figure 1F). To investigate the association of CD74+ TAMs with AML cells, Gene Set Variation Analysis (GSVA) was employed and revealed restrained pathways related to T cell function (Figure 2A). Through in vitro experiments on patient samples, we found that CD74+TAM can inhibit the proliferation of T cells and the secretion of IFN-γ. Further monoclonal antibody block experiments unveiled that this inhibitory effect might be attributed to the heightened expression of PD-L1, TGFβ1, and IL-10 by the macrophages (Figure 2B-C). In conclusion, we have substantiated the inhibitory role of CD74+ TAMs on T cells, which hampers their ability to engage in effective tumor killing. To elucidate the interplay between CD74+ TAMs and AML cells, we examined the gene expression profile of cytokines, noting a significant increase in the expression level of IL-6 within the CD74+ TAMs subclusters of the RE group (Figure 3A). Furthermore, upon co-culture with CD74+ TAMs, THP-1 cells exhibited notable activation of IL-6 related pathways (Figure 3B). The injection of CD74+ TAMs resulted in heightened AML initiation and poorer survival in patient-derived xenograft (PDX) model, which was reversed by blocking the IL-6-IL-6R axis (Figure 3C-D). These findings collectively confirm that IL-6 secreted by CD74+ TAMs fosters the malignancy and drug resistance of AML cells. Subsequently, MLL-AF9-induced AML mouse model was employed to explore the spatial interplay between CD74+ TAMs, AML cells and T cells. Immunofluorescence (IF) analysis of mouse bone marrow tissue revealed that after chemotherapy, the proximity between AML cells and CD74+ TAMs decreased (Figure 4A-B). Conversely, the presence of T cells surrounding CD74+ TAMs increased (Figure 4C-D). These findings indicate that CD74+ TAMs can inhibit T cell function and directly influence AML cells within the tumor microenvironment. In summary, our study revealed a notable rise in the proportion of TAMs expressing CD74 in relapsed AML patients. These CD74+ TAMs were found to facilitate leukemia progression while concurrently inhibiting T cell immune surveillance in the context of AML. Thus, our findings indicate that CD74+ TAMs represent a distinct type of macrophages associated with AML relapse.

ETV6-ABL1 Fusion Gene Was Associated with a Poor Prognosis in Patients with Acute Myeloid Leukemia

Background:Acute myeloid leukemia (AML) is commonly characterized by chromosomal abnormalities that result in the formation of chimeric genes involved in leukemogenesis. ETV6-ABL1-a fusion gene results from a complex rearrangement involving translocation, inversion, or insertion of ETV6 into chromosomal band 9q34 or ABL1 into 12p13. This rare but recurrent genetic aberration is found in AML patients and is associated with a poor prognosis. Methods:A retrospective review was conducted of three relapsed AML patients with ETV6-ABL1 fusion genes screened by multiplex RT-PCR who were treated at Beijing Lu Daopei Hospital and Hebei Yanda Lu Daopei Hospital between November 2019 and January 2022. Results:At diagnosis, the median age was 32 years (range 32-42 years), and two patients were male(Pt.2,3). AML subtypes included M2 (Pt.2) and M4 (Pt.1,3), and no patient had a prior history of myeloproliferative neoplasms. Clinical and laboratory characteristics at diagnosis included: hepatosplenomegaly (Pt.3), lymphadenopathy (Pt.1), leukocytosis (median 209.71×10 9 /L, range, 60.28-687.2×10 9/L),but no significant eosinophilia(≥1.5×10 9/L). Cytogenetic analyses showed a normal karyotype in all three patients. FLT3-ITD gene mutation was found in two patients(Pt.1,2). All there patients received the same IA regimen(idarubicincytarabine) as induction chemotherapy and achieved complete remission, followed by multi-agent chemotherapy as consolidation treatment.Pt.1 received additional targeted therapy with sorafenib. However, after a median duration of remission (DOR) of 4 months (range 3-8 months), all patients experienced relapse and sought for further therapy at our hospital. Upon re-evaluation by laboratory tests, ETV6-ABL1 fusion gene was detected by multiplex RT-PCR, and additional NUP98-NSD1 fusion was also found in Pt.2. FLT3-ITD gene mutation was confirmed in Pt. 1 and Pt. 2, but the characteristic t(9;12) (q34;p13) chromosomal abnormalities were not present in any of the patients. Pt. 2 presented with an abnormal karyotype of 46, XY, t(3;17)(q12;p11.2),add (10)(q22)[5] / 46,XY[15], while the rest 2 patients had a normal karyotype. Pt.1 died rapidly from serious infection after relapse. Pt. 2 and Pt. 3 received dasatinib-containing combination regimens as salvage therapy and achieved partial remission. Pt. 2 underwent haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT) with an enhanced myeloablative conditioning regimen in March 2021, and has maintained molecular remission until now. Pt. 3 is currently undergoing HSCT preparation. Conclusion: ETV6-ABL1 fusion gene is a rare but recurrent genetic aberration in AML, and its rearrangement is not uniform across eachpatient, typically involving cryptic insertions. Routine chromosome G-banding analysis may not identify this fusion gene, and the combined use of fluorescence in situ hybridization and PCR is recommended for better detection for ETV6-ABL1. Patients with this fusion gene have a high relapse rate and a poor prognosis. Tyrosine kinase inhibitors (eg. Dasatinib)are a reasonable treatment option, and allo-HSCT may be considered for potential cure.

Detection of Cryptic Gene Fusion and Chimeric RNA Variants in Relapsed/Refractory Acute Myeloid Leukemia Patients Diagnosed with KMT2A/Afdn Chromosomal Translocation

Chromosomal rearrangements, such as translocations, play a significant role in creating chimeric genes and oncofusion proteins initiating leukemogenesis in 52% of acute myeloid leukemia (AML) patients, and are associated with an adverse prognosis. Currently, there are limited targeted therapies available for AML patients with chromosome rearrangements primarily due to a lack of accurate molecular and genetic characterization of the mechanism of leukemic progression along the treatment course. In our study, we investigated the pathological landscape of treatment resistance and relapse in AML patients with KMT2A-rearranged gene fusions (previously known as mixed lineage leukemia, MLL gene, 11q23), which is one of the most common gene rearrangements in AML with a dismal prognosis. Our approach included chromosome analysis, fluorescence in situ hybridization (FISH), transcriptomic analyses (RNA-seq), polymerase chain reaction (PCR), DNA-sequencing and quantitative PCR (qPCR) were applied to monitor RNA- and genome-wide changes among newly diagnosed, refractory and relapsed AML patients. Bone marrow samples of seven AML patients with different chromosome were obtained and two samples were found to possess the chromosomal translocation t(6;11)(q27;q23) which leads to KMT2A/AFDN gene fusion. In these patients, RNA-seq identified a cryptic CCDC32 (15q15.1) /CBX3 (7p15.2) gene fusion in both newly diagnosed and relapsed samples, which is previously unreported in KMT2A/AFDN-rearranged AML patients. Quantitative gene expression measurement by qPCR demonstrated that CCDC32/CBX3 gene fusion significantly affected the expression of wild-type genes of CCDC32 (essential for embryonic development) and CBX3 (an oncogene for solid tumors) during the relapse, suggesting the potential oncogenic role for the CCDC32/CBX3 chimera in AML development. Our result is consistent with a previous study showing multiple breakpoints in AML patients with KMT2A/AFDN translocations. KMT2A rearrangements are known to have an unfavorable prognosis in AML and the specific t(6;11)(q27;23) translocation in AML patients leads to a median overall survival of only 12 months. Our novel findings also suggest that one reason for the adverse outcomes of KMT2A chromosomal rearrangements is their complex ability to generate chimeric variants and more aggressive subclones to elude the treatment. Our study implies that standard cytogenetic analyses and emerging NGS are not sufficient to fully diagnose a patient with chromosome rearrangement. Particularly, short-read RNA-seq presents problems because it cannot detect gene fusions with low expression level, like the KMT2A/AFDN gene fusion that was undetected in patient 7 by our short-read RNA-seq. Instead, long-read RNA-seq, combined with cytogenetics and molecular profiling through PCR/Sanger DNA-sequencing, should be utilized to identify complex fusion transcripts and different chimeric variants of multiple gene fusions.

Low doses of IFN-γ maintain self-renewal of leukemia stem cells in acute myeloid leukemia.

Conventional therapies for acute myeloid leukemia (AML) often fail to eliminate the disease-initiating leukemia stem cell (LSC) population, leading to disease relapse. Interferon-γ (IFN-γ) is a known inflammatory cytokine that promotes antitumor responses. Here, we found that low serum IFN-γ levels correlated with a higher percentage of LSCs and greater relapse incidence in AML patients. Furthermore, IFNGR1 was overexpressed in relapsed patients with AML and associated with a poor prognosis. We showed that high doses (5-10 μg/day) of IFN-γ exerted an anti-AML effect, while low doses (0.01-0.05 μg/day) of IFN-γ accelerated AML development and supported LSC self-renewal in patient-derived AML-LSCs and in an LSC-enriched MLL-AF9-driven mouse model. Importantly, targeting the IFN-γ receptor IFNGR1 by using lentiviral shRNAs or neutralizing antibodies induced AML differentiation and delayed leukemogenesis in vitro and in mice. Overall, we uncovered essential roles for IFN-γ and IFNGR1 in AML stemness and showed that targeting IFNGR1 is a strategy to decrease stemness and increase differentiation in relapsed AML patients.

Gemtuzumab Ozogamicin Monotherapy Is a Well-tolerated Palliative Chemotherapy Option in Pediatric Multiply Relapsed Acute Myeloid Leukemia: A Multicenter Case Series and Review of the Literature.

Gemtuzumab ozogamicin (GO) is an anti-CD33 antibody that is Food and Drug Administration approved in upfront acute myeloid leukemia (AML) for patients over 1-month old, and for relapsed or refractory AML in patients over 2 years old. GO is now integrated in upfront pediatric AML treatment, and often in CD33+ relapse treatment combined with intensive conventional chemotherapy. Although GO was initially tested as a monotherapeutic agent in relapsed or refractory AML, there are few data in pediatric patients supporting this indication. In this review, we report 4 cases of multiply relapsed pediatric AML patients who were treated with GO monotherapy with palliative intent. Three of 4 patients obtained a complete response with GO reinduction, either as monotherapy or paired with conventional chemotherapy. Three patients remained in remission respectively for 5, 17, and 9 months with GO continuation monotherapy. The literature was reviewed regarding the use of GO in pediatric AML relapse settings.

Clinical-grade natural killer cells expanded from donor peripheral blood and anti-leukemia effect against myeloid leukemia.

e19018 Background: Natural killer (NK) cells play a crucial role in immune surveillance and tumor clearance. It has been reported that allogeneic NK cell therapy has good safety and curative effect in patients with refractory and relapsed acute myeloid leukemia (AML). However, the clinical application of adoptive NK infusion is limited due to the lower number of human NK cells. We established a feeder-free NK cell expansion system from peripheral blood (PB) and explore the anti-leukemia potential in preclinical and clinical studies. Methods: The killing capacity of ex vivo-expanded NK cells were detected by Flow cytometry. The in vivo expansion, survival and anti-leukemia activity of the expanded NK cells were detected in K562-bearing NSG mice. Six AML patients with hematological/extra medullary relapsed (n = 3) or persistent positive minimal residual disease (n = 3) after consolidation and maintenance therapy were enrolled in Peking University Institute of Hematology from 2021 to 2022. The patients were treated with high-dose cyclophosphamide and fludarabine, then combined with adoptive infusion of donor-derived expanded NK cells. The chimerism, the number and function of NK cells were analyzed, and the safety and clinical efficacy were evaluated. Results: The ex vivo-expanded NK cells exhibit highly anti-leukemia activity. NK cells proliferate in mice and the CD56+ cells to reach the peak time in each organ is 3-7 days and drop to the level before infusion after 14 days. NK cell infusion significantly improve the survival of leukemia mice, and the anti-leukemia effect is NK cell dose-dependent. In the clinical trial, six patients received a total of 7 cases of NK cell infusion, including 3 cases in low-dose group and 4 cases in middle-dose group, among which 1 patient received 2 dose (1 low-dose and 1 middle-dose). In the low-dose group, 1 patient got response (1/3), with the minimal residual disease turned negative. In the middle-dose group, 3 patients responded (3/4), of which 1 patient had the fusion gene CBFB /ABL decreased from 0.99% to 0.13%, 1 case of extramedullary recurrence of AML turned negative, and NK cells could be detected in cerebrospinal fluid, 1 case of hematological recurrence got hematological remission after treatment. The survival time of NK cells in vivo was 7d-30d, with longer time in middle dose group than those in low dose group. The proportion and number of NK cells in responding cases were significantly higher than those in non-responsive group. Conclusions: Clinical grade expanded NK cells has strong anti-leukemia activity in patients with relapse or minimal residual positive AML patients. NK cells can survive for 2 weeks and can enter the central nervous system without obvious adverse reactions. The response rate in middle-dose group is higher than that in low-dose group. However, the efficacy of NK cells still needs to be further confirmed in a large sample size. Clinical trial information: NCT04221971 .

Immune-related genetic prognostic index to predict prognosis and immune checkpoint inhibitor therapy efficiency in acute myeloid leukemia.

Immune-related genetic prognostic index to predict prognosis and immune checkpoint inhibitor therapy efficiency in acute myeloid leukemia.

Abstract 1594: SMARCA2 (BRM) degraders promotes differentiation and inhibit proliferation in AML models

Abstract Dysregulated cellular differentiation is a major pathological feature of myeloid malignancies such as acute myeloid leukemia (AML). Targeting cellular differentiation programs has emerged as a novel therapeutic approach to treat patients with AML. Advantages of such differentiation therapy may include fewer systemic side-effects as well as opportunities to target leukemic stem cells (LSCs) and a broader range of clonal populations, likely resulting in lower frequencies of resistance and relapse in AML patients. The success of ATRA and decitabine in subsets of AML patients has proven that inducing differentiation can play a critical role in long-term durable responses. More agents targeting epigenetic regulators have been increasingly studied as differentiation inducers, including LSD1, DNMT1, Menin, and BET inhibitors. Recently, targeting SWI/SNF chromatin remodeling complexes has also been shown to regulate key leukemic gene expression signatures and induce AML differentiation. Small molecule inhibitors as well as gene knockdown for ATP-dependent SWI/SNF subunits SMARCA2 (BRM) and SMARCA4 (BRG1) are associated with re-direction of oncogenic transcriptional regulation to drive cellular differentiation and apoptosis in AML models. We have previously described the activity of highly potent, bispecific SMARCA2 degraders that efficiently promote SMARCA2 protein degradation in preclinical models. In the present study, we investigated the effects of our SMARCA2 selective degraders in AML models. Treatment with SMARCA2 degraders significantly inhibits AML cell line proliferation in vitro with IC50 ranging from 10 to 50 nM. In the SMARCA2 degrader treated cells, expression of PU.1 (SPI1), a key transcription factor in myeloid leukemias, was downregulated. In an in vivo OCI-AML3 xenograft model, treatment with a SMARCA2 selective degrader showed moderate tumor growth inhibition accompanied by robust increases in monocytic maturation markers CD11b and CD14. Further analyses of SMARCA2 degrader effects on global transcriptome and AML immunophenotypes as well as combination effects with other therapies are currently in progress. These findings highlight the potential of SMARCA2 degraders to target AML differentiation blocks and to improve the effectiveness of other therapeutic agents such as decitabine and venetoclax in AML patients. Citation Format: Anjana Agarwal, Olusola Peace Osinubi, Komali Vykuntam, Norman Fultang, Neha Bhagwat, Diane Heiser, Kris Vaddi, Koichi Ito, Peggy Scherle. SMARCA2 (BRM) degraders promotes differentiation and inhibit proliferation in AML models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1594.

Abstract 6314: Novel granzyme B-based fusion constructs targeting FRα on liquid and solid tumors

Abstract Folate receptor α (FRα) has been an attractive therapeutic target for many decades because it is highly overexpressed on several solid tumors and demonstrates low or restricted distribution on healthy tissues. Additionally, high expression of FRα has been associated with tumor progression and thus poor prognosis of cancer patients. Therefore, utilizing FRα to effectively locate tumor cells for targeted therapy using antibody drug conjugates, small molecule drug conjugates, radioimmunoconjugates or chimeric antigen receptor T cells, has been extensively investigated. Although some of the mentioned targeted therapies have shown promising preclinical results, their clinical utility has been limited due to associated toxicities in healthy tissues. We generated two new fusion constructs targeting FRα and containing active human granzyme B (GrB) as the cytotoxic payload. We used as binding domains two different scFvs targeting the FRα from antibodies previously used in clinical trials. These human scFvs (mov003 and mov018) were fused to the human serine protease GrB through an engineered human IgG heavy-chain fragment (designated as Fc) which contains a dimerization domain for longer half-life. The cytotoxicity of the constructs against a panel of cell lines expressing various levels of FRα showed a specific cytotoxic effect with an IC50 in the low nanomolar range (5-100 nM), particularly exhibiting very low IC50 values against breast and ovarian cell lines. FRα negative cells demonstrated IC50 levels in the micromolar range. Immunofluorescence studies demonstrated that the fusion constructs targeting FRα are efficiently internalized and effectively delivered the active serine protease to the cytosol. In vitro stability assays over 96 hours showed that both constructs are highly stable in mouse serum. Additionally, recent publications suggested that FRα is significantly associated with acute myeloid leukemia (AML) and might serve as a therapeutic target. We assessed the cytotoxic efficacy of GrB-based constructs on a panel of FRα+ AML cell lines and have found that these cell lines were very sensitive (IC50 in the low nanomolar range). Furthermore, evaluation of GrB fusion efficacy in two AML cell lines resistant to Bcl-2 inhibitor Venetoclax showed IC50s to be similar or lower than their parental cell lines. These results, therefore, demonstrate no cross-resistance to GrB. The safe and effective profile of these drugs together with their unique mechanism of action makes them ideal candidates for advancing pre-clinical development and may offer a potential new strategy for treatment of solid tumors and particularly Venetoclax relapsed AML patients, ineligible for intensive chemotherapy. In vivo efficacy studies to compare the two constructs are warranted and will help to identify the optimal therapeutic for further clinical consideration. Research conducted, in part, by the Clayton Foundation for Research. Citation Format: Ana Alvarez-Cienfuegos, Lawrence H. Cheung, Khalid A. Mohamedali, Natalia Baran, Marina Konopleva, Michael G. Rosenblum. Novel granzyme B-based fusion constructs targeting FRα on liquid and solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6314.

An NGS based MRD evaluation from acute myeloid leukemia patients.

Measurable residual disease (MRD) is a prognostic factor for acute myeloid leukemia (AML). A next-generation sequencing (NGS) based MRD panel was developed and the results were validated. The NGS sequencing data was collected from 1003 Chinese AML patients. The sequencing data from 586 newly diagnosed AML patients showed that NRAS mutation was most common (20.8%), followed by NPM1 (19.4%), FLT3-ITD (18.5%), and DNMT3A (15.4%). NPM1 and FLT3-ITD mutations were less in Chinese than in Caucasian AML patients, and the result of KRAS mutation was opposite. A new panel named "AML NGS-MRD hot-spot panel" was designed, containing 178 hot-spot exons from 52 mutated genes and only 62.8 Kb in size. With this hot-spot panel, 92.5% newly diagnosed AML patients were found to carry ≥1 mutations. To verify the performance of this panel, additional 205 newly diagnosed AML patients and 212 post-treatment AML patients were evaluated, and the hot-spot panel achieved a similar detection rate (91.2% for newly diagnosed AML patients and 89.2% for post-treatment AML patients). Finally, this study found that the mutation frequencies of signaling pathway genes (e.g., KRAS, NRAS, FLT3-ITD, KIT) were significantly reduced in post-treatment AML. The "AML NGS-MRD hot-spot panel" detected the mutations from relapsed AML patients with minimal panel size, and was a reliable and cost-effective panel for AML patients.

Combination of Menin and IDH Mutant Inhibition in Acute Myeloid Leukemia

The interaction between menin and mixed lineage leukemia 1 (MLL1) protein contributes to abnormal proliferation in the MLL1-(KMT2A) rearranged and nucleophosmin 1 (NPM1)-mutated acute myeloid leukemia (AML). Indeed, small molecule inhibition of the menin/MLL1 interaction was shown to inhibit leukemia in both AML subtypes. Approximately 25% of NPM1 mutated AML also carry an IDH 1 or 2 mutation. Carrying both NPM1- and IDH mutations is associated with worse overall survival and relapse free survival, compared to having only the NPM1 mutation. MI-3454, a small molecule inhibitor of MLL1/menin interaction, has been shown to be effective in AML with KMT2A rearrangements and NPM1 mutations. A close analogue of this compound, KO-539 (Ziftomenib) is now being tested in clinical trials in refractory and relapsed AML patients (NCT 04067336). The aim of this study is to determine the efficacy of the combination of MI-3454 and IDH mutant inhibitors in AML carrying concurrent NPM1 and IDH1/2 mutations. Blood or bone marrow aspirate samples from patients with AML harboring both NPM1 and IDH1 and/or IDH2 mutations were obtained and used to assess the effect of combinatorial treatment of menin and IDH mutant inhibitors. Colony formation assays with these AML patient samples were performed in methylcellulose media with cells treated with a concentration range of MI-3454, ivosidenib (IDH1 inhibitor) or enasidenib (IDH2 inhibitor) as single agents and in combinations. At the end point of the experiments, colonies were counted. Cells were collected for 1) cytohistology to assess cell morphology 2) flow cytometry to evaluate markers of differentiation and apoptosis and 3) gene expression studies to assess the effect of the combinations on the expression level of genes implicated in leukemogenesis and differentiation. In the samples with concurrent NPM1 and IDH1 mutations, the combination of MI-3454 and ivosidenib caused synergistic reduction in colony number compared to the single agents, with combination indices (CI) ranging from 0.44 to 0.94. Furthermore, cells treated with this combination demonstrated more differentiating phenotypes than single agent treated cells. In the samples with concurrent NPM1 and IDH2 mutations, the combination of MI-3454 and enasidenib caused synergistic reduction in colony formation versus either single agent MI-3454 or enasidenib, with CI values 0.12-0.64. The combination of these agents also yielded stronger differentiation than single agents alone based on both morphologic assessment and enhanced expression of CD11B differentiation marker. Mechanistically, the combination of MI-3454 and IDH1/2 mutant inhibitors also more significantly decreased the expression of HOXA9, MEIS1, and HOXB2, which are oncogenes implicated in leukemogenesis, over single agents. The expression of MNDA was also significantly enhanced by these combinations, supporting differentiation. Overall, our study demonstrates that combination of MI-3454 and IDH mutant inhibitors outperforms the effect of single agents with respect to their anti-leukemic effects in clinically relevant pre-clinical models. These results support that combination of menin and IDH mutant inhibitors could be utilized in clinical trials to improve the ability of patients with AML to achieve remission.

Revised Prognostic Index for Patients with Acute Myeloid Leukemia and Other High-Grade Myeloid Neoplasms in First Relapse

Introduction: Though many patients with acute myeloid leukemia (AML) will achieve a first complete remission (CR1), most patients will relapse. A previous analysis from HOVON on 667 consecutive AML patients in first relapse identified four key predictors for achieving a second CR (CR2), which improved overall survival (OS): age at relapse, CR1 duration, cytogenetic risk, and prior receipt of hematopoietic cell transplant (HCT), thereby developing a scoring system to aid in therapeutic decision making (Breems, JCO 2005). Since this original publication, other predictors of relapse have emerged, most notably measurable residual disease (MRD), and cytogenetic/molecular risk stratification has been refined in the form of ELN2017 (Dohner, Blood 2017). We hypothesize that incorporation of MRD and ELN2017 categorization into a risk stratification model will improve our ability to predict CR2 likelihood and OS after relapse. Methods: Eligible patients included those ≥18 years (yrs) old who received treatment (tx) at our center for AML or other high-grade myeloid neoplasms (≥10% marrow/peripheral blasts at diagnosis) between January 2008 and July 2019, who later relapsed. Using our IRB-approved institutional AML database, we obtained the following demographic and outcome parameters: age; gender; new diagnosis (ND) type (AML vs. other; de novo vs. secondary); ECOG performance status; TRM score; ELN2017 risk; CR1 date; CR1 details [CR vs. CR with incomplete hematologic recovery (CRi) and MRD status]; initial tx intensity [low being hypomethylating agents (HMA); intermediate being 7+3 or similar; high being FLAG-ida/CLAG-M or similar]; cycles to CR1; prior HMA before relapse; prior HCT before relapse; relapse date; relapse salvage tx type and intensity; response to salvage (CR vs. CRi + MRD status); CR2 date; subsequent HCT; and death date or date of last contact. We fit multivariable (MV) models for OS after first relapse (Cox) and CR2 after first relapse (logistic). A score for each respective outcome was developed by rounding the coefficients from the models. C-statistics (Cox) and area under the receiver operating characteristic curve (AUC; logistic) were also calculated. Results: We identified 315 eligible patients who achieved CR1 and relapsed. Among these, 266 received subsequent tx and were included in our analysis: the median age at relapse was 63 yrs (range 20-85); 40% (n=106) were female; 56% (n=148) received high-intensity tx for ND; 47% (n=125) had secondary AML at ND; 28% (n=75) had received prior HCT before relapse; 36% (n=95) had received prior HMA before relapse. For initial tx of first relapse, 52% (n=138) received high-intensity tx; 5% (n=13) received HCT; 12% (n=31) received intermediate-intensity tx; and 32% (n=84) received low-intensity tx. Overall, 60% (n=160) achieved a subsequent CR2. Significant covariates in the CR2 MV model were CRi following ND tx (odds ratio [OR] 0.85; 95% confidence interval [CI] 0.73-0.99), ≥2 cycles to CR1 (OR 0.86; CI 0.75-0.99), CR1 7-18 m (OR 1.22; CI 1.07-1.38), CR1>18 m (OR 1.31; CI 1.12-1.53), post-relapse HCT (OR 1.43; CI 1.1-1.86), and low-intensity tx post-relapse (OR 0.77; CI 0.68-0.87). Significant covariates leading to improved OS in the MV model were CR1 duration of 7-18 m (hazard ratio [HR] 0.5; 95% CI 0.36-0.69), CR1 duration >18 m (HR 0.36; CI 0.24-0.55); and post-relapse HCT (HR 0.49; CI 0.26-0.91). We derived scoring systems from these MV models (Table 1). A positive score indicates a favorable prognosis (median OS of 13.6 m); a score of 0 (median OS 6.5 m) or below (median OS 5.6 m) indicates a poor prognosis (Figure 1). When the Breems scoring system for OS was applied to our dataset, the C-statistic was 0.55; our score improved to a C-statistic of 0.61. The AUC for the CR2 score from our model was 0.69. Conclusions: The Breems system was not well-calibrated to our dataset, underscoring the need to develop an updated scoring model for OS and CR2 in relapsed AML patients. Surprisingly, factors such as CR1 MRD status and ELN2017 risk did not appear to be significant in MV analyses. Efforts are underway to update this dataset to include additional contemporary patients; we hope to enhance the prognostic scoring algorithm by capturing the effect of specific mutational profiling (e.g. TP53, FLT3, and others). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Gilteritinib Maintenance Therapy Post-Allogenic Stem-Cell Transplantation Improves the Prognosis of Patients with FLT3-Mutated AML

Introduction FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD) and -tyrosine kinase domain (TKD) mutation were common mutations in acute myeloid leukemia (AML). FLT3-ITD mutation adversely affected the outcome of hematopoietic stem-cell transplantation (SCT). While sorafenib and midostaurin as maintenance therapy after SCT prolonged relapse-free and overall survival (OS), there are very few reports of post-transplant gilteritinib maintenance therapy outside of clinical trials. Hence, to explore the efficacy of the gilteritinib maintenance therapy post-SCT, we here report the prognostic impact of post-SCT gilteritinib maintenance in a clinical setting. Methods We retrospectively analyzed 25 FLT3-mutated relapsed or refractory AML patients who received allogeneic SCT at our center from January 1, 2011 to April 30, 2022. FLT3 mutation was analyzed by a commonly used polymerase chain reaction (PCR)-based assay. Measurable residual disease (MRD) was assessed by Wilms tumor 1 (WT1) mRNA expression in peripheral blood, and MRD positivity was defined as WT-1 >50 copies/μg in this study. Relapse was defined as an increase of 5% blasts or more. Non-relapse mortality (NRM) was defined as death without relapse. Leukemia-free survival (LFS) was defined as the time from transplantation to leukemia relapse or death from any cause, which comes first. OS was defined as the time from transplantation to death from any cause. Results The median age was 52 years. Twenty-two patients had ITD mutation and 5 had TKD mutation (2 had both ITD and TKD mutation). At the time of the transplant, 20 patients were in remission (6 were MRD-negative and 14 were MRD-positive) and five were in non-remission. All patients achieved hematologic complete remission (CR) after SCT and no patients relapsed within 30 days post-SCT. After hematological engraftment, 14 patients started to receive gilteritinib as maintenance therapy and 11 patients did not. Between the two groups, the patients' characteristics including disease status at transplant, SCT procedures, and donor sources were well balanced except for the administration of FLT3-inhibitor prior to SCT (100% in patients with gilteritinib maintenance and 45.5% in those without gilteritinib maintenance, p = 0.003). Eleven patients (78.6%) in the gilteritinib group and eight (72.7%) patients in the non-gilteritinib group had residual MRD in hematological CR or were non-CR prior to SCT. The median time from SCT to the initiation of gilteritinib was 36 days. The median dose at gilteritinib initiation was 40mg (range 20-120 mg). One patient developed grade 2 skin acute graft-versus-host disease (GVHD) after gilteritinib administration and 4/14 patients (28.6%) developed moderate-severe chronic GVHD (cGVHD, two developed pulmonary cGVHD, one eye and mouse, and one skin) with a median onset of 10.5 months (range 3.1-30.5 months), while only one patient temporary discontinued gilteritinib until the improvement of cGVHD. Late engraftment failure during gilteritinib maintenance was not observed. In terms of survival benefit, patients with gilteritinib maintenance showed significantly longer LFS and OS than those without gilteritinib (1-y LFS; 100% vs. 36.4%, 95% CI; 100-100% vs. 11.2-62.7%, p = 0.0028, Figure A, and 1-y OS; 100% vs. 45.5%, 95% CI; 100-100% vs. 16.7-70.7%, p = 0.0075, Figure B). The cumulative incidence of AML relapse at one-year in patients with gilteritinib maintenance group was significantly lower than those without (0% vs. 51.5%, 95% CI; 0-0% vs. 24.9-86.0%, p = 0.005). Especially, among patients with MRD positive or non-CR prior to SCT (n=19), patients who received gilteritinib maintenance showed a lower cumulative incidence of AML relapse at one-year than those without gilteritinib maintenance (0% vs. 68.8%, 95% CI; 0-0% vs. 35.9-95.2%, p = 0.0028, Figure C). Patients without MRD prior to SCT did not relapse with or without gilteritinib maintenance. These results suggest that gilteritinib maintenance therapy contributes to preventing post-transplant relapse in patients who remain MRD positive at the time of SCT. Conclusion Gilteritinib maintenance therapy post-SCT showed survival benefit in a clinical setting. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

METTL3 mediates chemoresistance by enhancing AML homing and engraftment via ITGA4

Chemoresistant leukemia relapse is one of the most common causes of death for acute myeloid leukemia (AML) patients and the homing/engraftment in bone marrow (BM) are crucial steps for AML cells to acquire chemoresistance by interacting with stromal cell components. No crosstalk between m6A modification and homing/engraftment has been reported. Here, we performed comprehensive high-throughput analyses, including RNA sequencing of CR (complete remission) and relapsed AML patients, and reverse-phase protein arrays of chemoresistant cells to identify METTL3 as a key player regulating AML chemoresistance. Then, METTL3-mediated m6A modification was proved to induce the chemoresistance in vitro and in vivo. Furthermore, AML homing/engraftment was discovered being enhanced by upregulated-METTL3 in chemoresistant cells. And the homing/engraftment and drug-resistance associated phenotypes of chemoresistant cells could be reversed by a METTL3 inhibitor. Mechanistically, METTL3 extended the half-life of ITGA4 mRNA by m6A methylation, and then, increased expression of ITGA4 protein to enhance homing/engraftment of AML cells. The results provide insights into the function of m6A modification on the interaction between AML cells and BM niches and clarify the relationship between METTL3 and AML homing/engraftment, suggesting a therapeutic strategy for the treatment of refractory/relapsed AML with METTL3 inhibitors.

Recent Advances in the Development of Anti-FLT3 CAR T-Cell Therapies for Treatment of AML.

Following the success of the anti-CD19 chimeric antigen receptor (CAR) T-cell therapies against B-cell malignancies, the CAR T-cell approach is being developed towards other malignancies like acute myeloid leukemia (AML). Treatment options for relapsed AML patients are limited, and the upregulation of the FMS-like tyrosine kinase 3 (FLT3) in malignant T-cells is currently not only being investigated as a prognostic factor, but also as a target for new treatment options. In this review, we provide an overview and discuss different approaches of current anti-FLT3 CAR T-cells under development. In general, these therapies are effective both in vitro and in vivo, however the safety profile still needs to be further investigated. The first clinical trials have been initiated, and the community now awaits clinical evaluation of the approach of targeting FLT3 with CAR T-cells.

Immunotherapy targeting mesothelin in acute myeloid leukemia.

Mesothelin (MSLN) is an emerging target that exists in soluble and membrane-associated forms. It is usually used for the diagnosis and treatment of MSLN-positive solid tumors. Interestingly, recent studies have shown that MSLN is highly expressed in 36% of acute myeloid leukemia (AML) patients and barely expressed in normal hematopoietic cells, which makes MSLN a promising target for the treatment of AML. It has been shown that MSLN is detectable as a diagnostic marker in its soluble form. Although the mechanism of action is unclear, MSLN remains a promising target for immunotherapy. Most MSLN research has been conducted in solid tumors, and less research has been conducted in hematopoietic tumors. Increasing research on MSLN is underway in AML, a hematopoietic neoplasm. For example, MSLN is related to extramedullary disease, minimal residual disease, and relapse in AML patients. Decreasing the expression of MSLN reduces the severity of the disease course. This information suggests that MSLN may be an ideal target for the treatment of many AML-related diseases to improve the prognosis and survival rate. At present, there are a few immunotherapies targeting MSLN in AML in preclinical and clinical trials, such as antibody-drug conjugates, bispecific T-cell engagers, and chimeric antigen receptor-T cells, which opens new room for the treatment of MSLN-related AML.

Acute myeloid leukemia fusion genes can be found in CD33-negative cells.

Targeted therapies and immunotherapies are emerging strategies for the treatment of leukemia. CD33 is a common and important therapeutic target for cellular immunotherapy or antibody immunotherapy. Drugs on targeting CD33 are also emerging. However, acute myeloid leukemia (AML) relapse still occurs after treatment with targeted CD33, for which the mechanism is unknown. We used fluorescence in situ hybridization and real-time polymerase chain reaction to detect the expression of fusion genes in different populations of cells from AML patients. Fusion gene can be express in CD33 negative cell proportions in newly diagnosed and relapsed AML patients. There are fusion genes in CD33-negative cells that are might not be cleared by CD33 targeting therapy. And this might be the source of relapse.