Relapsed Acute Myeloid Leukemia Research Articles

Comprehensive insights into AML relapse: genetic mutations, clonal evolution, and clinical outcomes.

Acute myeloid leukemia (AML) is a complex hematologic malignancy characterized by uncontrolled proliferation of myeloid precursor cells within bone marrow. Despite advances in understanding of its molecular underpinnings, AML remains a therapeutic challenge due to its high relapse rate and clonal evolution. In this retrospective study, we analyzed data from 24 AML patients diagnosed at a single institution between January 2017 and August 2023. Comprehensive genetic analyses, including chromosomal karyotyping, next-generation sequencing, and gene fusion assays, were performed on bone marrow samples obtained at initial diagnosis and relapse. Clinical data, treatment regimens, and patient outcomes were also documented. Mutations in core genes of FLT3, NPM1, DNMT3A, and IDH2 were frequently discovered in diagnostic sample and remained in relapse sample. FLT3-ITD, TP53, KIT, RUNX1, and WT1 mutation were acquired at relapse in one patient each. Gene fusion assays revealed stable patterns, while chromosomal karyotype analyses indicated a greater diversity of mutations in relapsed patients. Clonal evolution patterns varied, with some cases showing linear or branching evolution and others exhibiting no substantial change in core mutations between diagnosis and relapse. Our study integrates karyotype, gene rearrangements, and gene mutation results to provide a further understanding of AML heterogeneity and evolution. We demonstrate the clinical relevance of specific mutations and clonal evolution patterns, emphasizing the need for personalized therapies and measurable residual disease monitoring in AML management. By bridging the gap between genetics and clinical outcome, we move closer to tailored AML therapies and improved patient prognoses.

Metabolic dependencies of acute myeloid leukemia stem cells.

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy primarily driven by an immature population of AML cells termed leukemia stem cells (LSCs) that are implicated in AML development, chemoresistance, and relapse. An emerging area of research in AML focuses on identifying and targeting the aberrant metabolism in LSCs. Dysregulated metabolism is involved in sustaining functional properties of LSCs, impeding myeloid differentiation, and evading programmed cell death, both in the process of leukemogenesis and in response to chemotherapy. This review discusses recent discoveries regarding the aberrant metabolic processes of AML LSCs that have begun to change the therapeutic landscape of AML.

Safety and Efficacy of High-Dose Chemotherapy with TreoMel 200 vs. TreoMel 140 in Acute Myeloid Leukemia Patients Undergoing Autologous Stem Cell Transplantation

(1) Background: Treosulfan and melphalan (TreoMel)-based high-dose chemotherapy (HDCT) has shown promising safety and efficacy as a conditioning regimen for acute myeloid leukemia (AML) patients undergoing autologous stem cell transplantation (ASCT). However, despite intensive first-line induction treatment and upfront consolidation with HDCT and ASCT, AML relapse rates are still high, and further efforts are needed to improve patient outcomes. The aim of this study was to compare two melphalan dose schedules in regard to the safety of TreoMel HDCT and patient outcomes. (2) Methods: We retrospectively analyzed the safety and efficacy of two melphalan dose schedules combined with standard-dose treosulfan in AML patients undergoing HDCT and ASCT at the University Hospital of Bern, Switzerland, between August 2019 and August 2023. Patients received treosulfan 42 g/m2 combined with either melphalan 140 mg/m2 (TreoMel 140) or melphalan 200 mg/m2 (TreoMel 200). Co-primary endpoints were progression-free survival (PFS), overall survival (OS), as well as safety profile. (3) Results: We included a total of 51 AML patients: 31 (60.8%) received TreoMel 140 and 20 (39.2%) TreoMel 200. The patients’ basal characteristics were comparable between both cohorts. No significant differences in the duration of hospitalization or the adverse event profile were identified. There were no statistically significant differences in relapse (0.45 vs. 0.30, p = 0.381) and mortality rates (0.42 vs. 0.15, p = 0.064) between the melphalan 140 mg/m2 and 200 mg/m2 cohorts, nor for PFS (HR: 0.81, 95% CI: 0.29–2.28, p = 0.70) or OS (HR: 0.70, 95% CI: 0.19–2.57, p = 0.59) for the TreoMel 140 vs. TreoMel 200 cohort. (4) Conclusions: A higher dose of melphalan (TreoMel 200) was well tolerated overall. No statistically significant differences for patient outcomes could be observed, possibly due to the relatively small patient cohort and the short follow-up. A longer follow-up and prospective randomized studies would be required to confirm the safety profile and clinical benefit.

Continuously improving outcome over time after second allogeneic stem cell transplantation in relapsed acute myeloid leukemia: an EBMT registry analysis of 1540 patients

Second allogeneic stem cell transplantation (alloSCT2) is among the most effective treatments for acute myeloid leukemia (AML) relapse after first alloSCT (alloSCT1). Long-term EBMT registry data were used to provide large scale, up-to-date outcome results and to identify factors for improved outcome. Among 1540 recipients of alloSCT2, increasing age, better disease control and performance status before alloSCT2, more use of alternative donors and higher conditioning intensity represented important trends over time. Between the first (2000–2004) and last (2015–2019) period, two-year overall and leukemia-free survival (OS/LFS) increased considerably (OS: 22.5–35%, LFS: 14.5–24.5%). Cumulative relapse incidence (RI) decreased from 64% to 50.7%, whereas graft-versus-host disease and non-relapse mortality (NRM) remained unchanged. In multivariable analysis, later period of alloSCT2 was associated with improved OS/LFS (HR = 0.47/0.53) and reduced RI (HR = 0.44). Beyond, remission duration, disease stage and patient performance score were factors for OS, LFS, RI, and NRM. Myeloablative conditioning for alloSCT2 decreased RI without increasing NRM, leading to improved OS/LFS. Haploidentical or unrelated donors and older age were associated with higher NRM and inferior OS. In summary, outcome after alloSCT2 has continuously improved over the last two decades despite increasing patient age. The identified factors provide clues for the optimized implementation of alloSCT2.

Clinicopathologic conference: Bloodstream infection in an allogeneic hamatopoietic cell transplant: Thinking beyond the usual.

This case involves a 53-year-old female with concurrent acute myeloid leukemia (AML) and multiple myeloma. She underwent cytarabine and daunorubicin (7+3) induction chemotherapy followed by cytarabine (HiDAC) consolidation, with an early AML relapse requiring azacitidine and venetoclax therapy. She achieved complete remission and incomplete count recovery. Following fludarabine, melphalan, and thymoglobulin induction chemotherapy, she underwent an allogeneic stem cell transplant with failure to engraft, requiring autologous stem cell rescue, buffy coat, and granulocyte transfusions, eventually presenting with a diffuse skin rash consistent with Steven-Johnson syndrome and toxic epidermal necrolysis, persistent neutropenic fevers and positive blood cultures.

Effects of total body irradiation on hematopoietic cell transplantation outcomes in pediatric acute myeloid leukemia with prior central nervous system involvement

BackgroundThe implications of previous central nervous system (CNS) involvement in children with acute myeloid leukemia (AML) undergoing hematopoietic cell transplantation (HCT) remain inadequately understood. Patients with CNS disease require more upfront CNS directed intrathecal therapy, but little is known about whether transplant conditioning regimens should be intensified or if previous CNS involvement impacts post HCT outcomes. While total body irradiation (TBI) remains standard for pediatric acute lymphoblastic leukemia myeloablative conditioning, it has been largely replaced with chemotherapy-only myeloablation in pediatric AML, primarily due to toxicity and late effects associated with TBI. In the setting of previous CNS involvement, it has been suggested that TBI-based myeloablation may have advantages due to superior CNS tissue penetration and thus decreased rates of AML relapse post HCT. ObjectiveWe analyzed a publicly available dataset derived from the Center of International Blood and Marrow Transplantation Research (CIBMTR) registry to characterize the impact of TBI in HCT preparative regimens in pediatric AML patients with a history of CNS involvement. MethodsThe study dataset was obtained from the CIBMTR data repository. The study cohort included patients aged ≤21 years who underwent initial allogeneic HCT with myeloablative conditioning for de novo AML in the first or second complete remission between 2008 and 2016, who provided consent for research. Patients with mismatched related donor transplant and non-calcineurin inhibitor graft-versus-host disease (GVHD) prophylaxis were excluded. The dataset was further modified by excluding patients with missing disease site data or those with non-CNS extramedullary disease. Patients were categorized as CNS-positive or -negative AML (AML-CNS(+) and AML-CNS(-), respectively) based on the disease status at diagnosis. Cox regression model and Fine Grey methods were employed to delineate the effects of TBI and CNS disease on key HCT outcomes. ResultsThe study cohort comprised 550 pediatric AML patients, of which 25% (n =136) were AML-CNS(+). CNS involvement was more prevalent in patients aged 0-3 years, patients who were in the second complete remission, and those with a mismatched unrelated donor or umbilical cord blood. AML-CNS(+) patients demonstrated a lower relapse rate (hazard ratio [HR]: 0.50, 95% confidence interval: 0.33-0.76) compared to AML-CNS(-) patients, with comparable disease-free survival (DFS) and overall survival (OS) (p =0.10 and 0.20, respectively) in the two cohorts. The entire TBI treated cohort showed an association with increased risks of Grade 2-4 acute GVHD, bloodstream infections, and endocrine dysfunction. TBI use within the AML-CNS(+) cohort was associated with a lower relapse rate but increased risks of non-relapse mortality and a trend of higher grade 3-4 acute GVHD. ConclusionIn this population-based analysis of pediatric patients with de novo AML undergoing HCT, TBI-based conditioning regimens did not confer an advantage in DFS or OS compared to non-TBI regimens, irrespective of CNS disease status. However, TBI use was associated with increased risks of short- and long-term comorbidities. These findings underscore the need for careful consideration of TBI in pediatric AML.

Clonal relapse dynamics in acute myeloid leukemia following allogeneic hematopoietic cell transplantation

AbstractPatients with acute myeloid leukemia (AML) who experience relapse following allogeneic hematopoietic cell transplantation (alloHCT) face unfavorable outcomes regardless of the chosen relapse treatment. Early detection of relapse at the molecular level by measurable residual disease (MRD) assessment enables timely intervention, which may prevent hematological recurrence of the disease. It remains unclear whether molecular MRD assessment can detect MRD before impending relapse and, if so, how long in advance. This study elucidates the molecular architecture and kinetics preceding AML relapse by using error-corrected next-generation sequencing (NGS) in 74 patients with AML relapsing after alloHCT, evaluating 140 samples from peripheral blood collected 0.6 to 14 months before relapse. At least 1 MRD marker became detectable in 10%, 38%, and 64% of patients at 6, 3, and 1 month before relapse, respectively. By translating these proportions into monitoring intervals, 38% of relapses would have been detected through MRD monitoring every 3 months, whereas 64% of relapses would have been detected with monthly intervals. The relapse kinetics after alloHCT are influenced by the functional class of mutations and their stability during molecular progression. Notably, mutations in epigenetic modifier genes exhibited a higher prevalence of MRD positivity and greater stability before relapse, whereas mutations in signaling genes demonstrated a shorter lead time to relapse. Both DTA (DNMT3A, TET2, and ASXL1) and non-DTA mutations displayed similar relapse kinetics during the follow-up period after alloHCT. Our study sets a framework for MRD monitoring after alloHCT by NGS, supporting monthly monitoring from peripheral blood using all variants that are known from diagnosis.

Integration of measurable residual disease by WT1 gene expression and flow cytometry identifies pediatric patients with high risk of relapse in acute myeloid leukemia.

Molecular testing plays a pivotal role in monitoring measurable residual disease (MRD) in acute myeloid leukemia (AML), aiding in the refinement of risk stratification and treatment guidance. Wilms tumor gene 1 (WT1) is frequently upregulated in pediatric AML and serves as a potential molecular marker for MRD. This study aimed to evaluate WT1 predictive value as an MRD marker and its impact on disease prognosis. Quantification of WT1 expression levels was analyzed using the standardized European Leukemia Network real-time quantitative polymerase chain reaction assay (qRT-PCR) among a cohort of 146 pediatric AML patients. Post-induction I and intensification I, MRD response by WT1 was assessed. Patients achieving a ≥2 log reduction in WT1MRD were categorized as good responders, while those failing to reach this threshold were classified as poor responders. At diagnosis, WT1 overexpression was observed in 112 out of 146 (76.7%) patients. Significantly high levels were found in patients with M4- FAB subtype (p=0.018) and core binding fusion transcript (CBF) (RUNX1::RUNX1T1, p=0.018, CBFB::MYH11, p=0.016). Following induction treatment, good responders exhibited a reduced risk of relapse (2-year cumulative incidence of relapse [CIR] 7.9% vs 33.2%, p=0.008). Conversely, poor responders' post-intensification I showed significantly lower overall survival (OS) (51% vs 93.2%, p<0.001), event-free survival (EFS) (33.3% vs 82.6%, p<0.001), and higher CIR (66.6% vs 10.6%, p<0.001) at 24 months compared to good responders. Even after adjusting for potential confounders, it remained an independent adverse prognostic factor for OS (p=0.04) and EFS (p=0.008). High concordance rates between WT1-based MRD response and molecular MRD were observed in CBF patients. Furthermore, failure to achieve either a 3-log reduction by RT-PCR or a 2-log reduction by WT1 indicated a high risk of relapse. Combining MFC-based and WT1-based MRD results among the intermediate-risk group identified patients with unfavorable prognosis (positive predictive value [PPV] 100%, negative predictive value [NPV] 85%, and accuracy 87.5%). WT1MRD response post-intensification I serves as an independent prognostic factor for survival in pediatric AML. Integration of WT1 and MFC-based MRD results enhances the reliability of MRD-based prognostic stratification, particularly in patients lacking specific leukemic markers, thereby influencing treatment strategies.

Convergent epigenetic evolution drives relapse in acute myeloid leukemia.

Relapse of acute myeloid leukemia (AML) is highly aggressive and often treatment refractory. We analyzed previously published AML relapse cohorts and found that 40% of relapses occur without changes in driver mutations, suggesting that non-genetic mechanisms drive relapse in a large proportion of cases. We therefore characterized epigenetic patterns of AML relapse using 26 matched diagnosis-relapse samples with ATAC-seq. This analysis identified a relapse-specific chromatin accessibility signature for mutationally stable AML, suggesting that AML undergoes epigenetic evolution at relapse independent of mutational changes. Analysis of leukemia stem cell (LSC) chromatin changes at relapse indicated that this leukemic compartment underwent significantly less epigenetic evolution than non-LSCs, while epigenetic changes in non-LSCs reflected overall evolution of the bulk leukemia. Finally, we used single-cell ATAC-seq paired with mitochondrial sequencing (mtscATAC) to map clones from diagnosis into relapse along with their epigenetic features. We found that distinct mitochondrially-defined clones exhibit more similar chromatin accessibility at relapse relative to diagnosis, demonstrating convergent epigenetic evolution in relapsed AML. These results demonstrate that epigenetic evolution is a feature of relapsed AML and that convergent epigenetic evolution can occur following treatment with induction chemotherapy.

Unveiling novel insights in acute myeloid leukemia through single-cell RNA sequencing.

Acute myeloid leukemia (AML) is a complex and heterogeneous group of aggressive hematopoietic stem cell disease. The presence of diverse and functionally distinct populations of leukemia cells within the same patient's bone marrow or blood poses a significant challenge in diagnosing and treating AML. A substantial proportion of AML patients demonstrate resistance to induction chemotherapy and a grim prognosis upon relapse. The rapid advance in next generation sequencing technologies, such as single-cell RNA-sequencing (scRNA-seq), has revolutionized our understanding of AML pathogenesis by enabling high-resolution interrogation of the cellular heterogeneity in the AML ecosystem, and their transcriptional signatures at a single-cell level. New studies have successfully characterized the inextricably intertwined interactions among AML cells, immune cells and bone marrow microenvironment and their contributions to the AML development, therapeutic resistance and relapse. These findings have deepened and broadened our understanding the complexity and heterogeneity of AML, which are difficult to detect with bulk RNA-seq. This review encapsulates the burgeoning body of knowledge generated through scRNA-seq, providing the novel insights and discoveries it has unveiled in AML biology. Furthermore, we discuss the potential implications of scRNA-seq in therapeutic opportunities, focusing on immunotherapy. Finally, we highlight the current limitations and future direction of scRNA-seq in the field.

Remission induction versus immediate allogeneic haematopoietic stem cell transplantation for patients with relapsed or poor responsive acute myeloid leukaemia (ASAP): a randomised, open-label, phase 3, non-inferiority trial

Whether high-dose cytarabine-based salvage chemotherapy, administered to induce complete remission in patients with poor responsive or relapsed acute myeloid leukaemia scheduled for allogeneic haematopoietic stem-cell transplantation (HSCT) after intensive conditioning confers a survival advantage, is unclear. To test salvage chemotherapy before allogeneic HSCT, patients aged between 18 and 75 years with non-favourable-risk acute myeloid leukaemia not in complete remission after first induction or untreated first relapse were randomly assigned 1:1 to remission induction with high-dose cytarabine (3 g/m2 intravenously, 1 g/m2 intravenously for patients >60 years or with a substantial comorbidity) twice daily on days 1-3 plus mitoxantrone (10 mg/m2 intravenously) on days 3-5 or immediate allogeneic HSCT for the disease control group. Block randomisation with variable block lengths was used and patients were stratified by age, acute myeloid leukaemia risk, and disease status. The study was open label. The primary endpoint was treatment success, defined as complete remission on day 56 after allogeneic HSCT, with the aim to show non-inferiority for disease control compared with remission induction with a non-inferiority-margin of 5% and one-sided type 1 error of 2·5%. The primary endpoint was analysed in both the intention-to-treat (ITT) population and in the per-protocol population. The trial is completed and was registered at ClinicalTrials.gov, NCT02461537. 281 patients were enrolled between Sept 17, 2015, and Jan 12, 2022. Of 140 patients randomly assigned to disease control, 135 (96%) proceeded to allogeneic HSCT, 97 (69%) after watchful waiting only. Of 141 patients randomly assigned to remission induction, 134 (95%) received salvage chemotherapy and 128 (91%) patients subsequently proceeded to allogeneic HSCT. In the ITT population, treatment success was observed in 116 (83%) of 140 patients in the disease control group versus 112 (79%) of 141 patients with remission induction (test for non-inferiority, p=0·036). Among per-protocol treated patients, treatment success was observed in 116 (84%) of 138 patients with disease control versus 109 (81%) of 134 patients in the remission induction group (test for non-inferiority, p=0·047). The difference in treatment success between disease control and remission induction was estimated as 3·4% (95% CI -5·8 to 12·6) for the ITT population and 2·7% (-6·3 to 11·8) for the per-protocol population. Fewer patients with disease control compared with remission induction had non-haematological adverse events grade 3 or worse (30 [21%] of 140 patients vs 86 [61%] of 141 patients, χ2 test p<0·0001). Between randomisation and the start of conditioning, with disease control two patients died from progressive acute myeloid leukaemia and zero from treatment-related complications, and with remission induction two patients died from progressive acute myeloid leukaemia and two from treatment-related complications. Between randomisation and allogeneic HSCT, patients with disease control spent a median of 27 days less in hospital than those with remission induction, ie, the median time in hospital was 15 days (range 7-64) versus 42 days (27-121, U test p<0·0001), respectively. Non-inferiority of disease control could not be shown at the 2·5% significance level. The rate of treatment success was also not statistically better for patients with remission induction. Watchful waiting and immediate transplantation could be an alternative for fit patients with poor response or relapsed acute myeloid leukaemia who have a stem cell donor available. More randomised controlled intention-to-transplant trials are needed to define the optimal treatment before transplantation for patients with active acute myeloid leukaemia. DKMS and the Gert and Susanna Mayer Stiftung Foundation.

Combining CRISPR-Cas9 and TCR exchange to generate a safe and efficient cord blood-derived T cell product for pediatric relapsed AML

BackgroundHematopoietic cell transplantation (HCT) is an effective treatment for pediatric patients with high-risk, refractory, or relapsed acute myeloid leukemia (AML). However, a large proportion of transplanted patients eventually die due...

Characterization of relapse-supportive monocytic cells in acute myeloid leukemia

The precise identities of bone marrow resident cells contributing to AML relapse are not fully known. Hollands etal. report early evidence to support the existence of an aberrant monocytic cell population that appears to promote LSC expansion after cytarabine treatment.

Pharmacological p38 MAPK inhibitor SB203580 enhances AML stem cell line KG1a chemosensitivity to daunorubicin by promoting late apoptosis, cell growth arrest in S-phase, and miR-328-3p upregulation

Acute myeloid leukaemia (AML) is characterized by uncontrolled proliferation of myeloid progenitor cells and impaired maturation, leading to immature cell accumulation in the bone marrow and bloodstream, resulting in hematopoietic dysfunction. Chemoresistance, hyperactivity of survival pathways, and miRNA alteration are major factors contributing to treatment failure and poor outcomes in AML patients. This study aimed to investigate the impact of the pharmacological p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 on the chemoresistance potential of AML stem cell line KG1a to the therapeutic drug daunorubicin (DNR). KG1a and chemosensitive leukemic HL60 cells were treated with increasing concentrations of DNR. Cell Titer-Glo®, flow cytometry, phosphokinase and protein arrays, Western blot technology, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were employed for assessment of cell viability, half-maximal inhibitory concentration (IC50) determination, apoptotic status detection, cell cycle analysis, apoptosis-related protein and gene expression monitoring. Confocal microscopy was used to visualize caspase and mitochondrial permeability transition pore (mPTP) activities. Exposed at various incubation times, higher DNR IC50 values were determined for KG1a cells than for HL60 cells, confirming KG1a cell chemoresistance potential. Exposed to DNR, late apoptosis induction in KG1a cells was enhanced after SB203580 pretreatment, defined as the combination treatment. This enhancement was confirmed by increased cleavage of poly(ADP-ribose) polymerase, caspase-9, caspase-3, and augmented caspase-3/-7 and mPTP activities in KG1a cells upon combination treatment, compared to DNR. Using phosphokinase and apoptosis protein arrays, the combination treatment decreased survival Akt phosphorylation and anti-apoptotic Bcl-2 expression levels in KG1a cells while increasing the expression levels of the tumor suppressor p53 and cyclin-dependent kinase inhibitor p21, compared to DNR. Cell cycle analysis revealed KG1a cell growth arrest in G2/M-phase caused by DNR, while combined treatment led to cell growth arrest in S-phase, mainly associated with cyclin B1 expression levels. Remarkably, the enhanced KG1a cell sensitivity to DNR after SB203580 pretreatment was associated with an increased upregulation of miR-328-3p and slight downregulation of miR-26b-5p, compared to DNR effect. Altogether, these findings could contribute to the development of a new therapeutic strategy by targeting the p38 MAPK pathway to improve treatment outcomes in patients with refractory or relapsed AML.

Macrophage migration inhibitory factor blockade reprograms macrophages and disrupts prosurvival signaling in acute myeloid leukemia

The malignant microenvironment plays a major role in the development of resistance to therapies and the occurrence of relapses in acute myeloid leukemia (AML). We previously showed that interactions of AML blasts with bone marrow macrophages (MΦ) shift their polarization towards a protumoral (M2-like) phenotype, promoting drug resistance; we demonstrated that inhibiting the colony-stimulating factor-1 receptor (CSF1R) repolarizes MΦ towards an antitumoral (M1-like) phenotype and that other factors may be involved. We investigated here macrophage migration inhibitory factor (MIF) as a target in AML blast survival and protumoral interactions with MΦ. We show that pharmacologically inhibiting MIF secreted by AML blasts results in their apoptosis. However, this effect is abrogated when blasts are co-cultured in close contact with M2-like MΦ. We next demonstrate that pharmacological inhibition of MIF secreted by MΦ, in the presence of granulocyte macrophage-colony stimulating factor (GM-CSF), efficiently reprograms MΦ to an M1-like phenotype that triggers apoptosis of interacting blasts. Furthermore, contact with reprogrammed MΦ relieves blast resistance to venetoclax and midostaurin acquired in contact with CD163+ protumoral MΦ. Using intravital imaging in mice, we also show that treatment with MIF inhibitor 4-IPP and GM-CSF profoundly affects the tumor microenvironment in vivo: it strikingly inhibits tumor vasculature, reduces protumoral MΦ, and slows down leukemia progression. Thus, our data demonstrate that MIF plays a crucial role in AML MΦ M2-like protumoral phenotype that can be reversed by inhibiting its activity and suggest the therapeutic targeting of MIF as an avenue towards improved AML treatment outcomes.

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 6728: Preclinical development of QL325, a novel T cell engager targeting CLEC12A-positive AML

Abstract Despite advancement in targeted therapies, treatment options for patients with acute myeloid leukemia (AML) that provide a tolerable and durable response remain elusive. We have developed a CD3 bispecific antibody, QL325, targeting CLEC12A, a c-type lectin protein that is highly expressed on AML blasts. Normally, CLEC12A expression is mostly confined to the CD34+CD38- progenitor population and largely absent on normal and regenerating bone marrow stem cells. Our bispecific antibody is configured in a 2 + 1 format, with bivalent avidity binding to CLEC12A, monovalent low affinity binding to CD3, and an effector-null Fc for extending half-life. In our preclinical studies, QL325 induced CLEC12A -dependent activation and proliferation of T cells. Redirected T cell-dependent cytotoxicity mediated by QL325 was restricted to AML cancer cells expressing CLEC12A. QL325 demonstrated dose dependent suppression of tumor growth in xenograft models of AML, significantly more potent than a clinical benchmark antibody. In non-human primates, QL325 was tolerated up to 0.03 mg/kg for IV dosing and under 0.1 mg/kg for SC dosing, well above the predicted effective therapeutic dose. A phase 1 clinical trial is currently ongoing to determine the safety and early efficacy in patients with refractory or relapsed AML. Citation Format: Shenda Gu, Hieu V. Tran, Shihao Chen, Ke Liu, Xin Zhang, Linchao Jia, Ruixue Ma, Jiayu Fu. Preclinical development of QL325, a novel T cell engager targeting CLEC12A-positive 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 6728.

Abstract 3400: Single-cell proteogenomics analysis of AML samples treated with decitabine and venetoclax reveals divergent treatment escape mechanisms

Abstract The combination therapy of hypomethylating agents and venetoclax (HMA+Ven) has emerged as a standard of care for acute myeloid leukemia (AML) patients unfit for intensive chemotherapy. Nonetheless, significant clinical challenges persist including relapse and treatment resistance, to which our understanding remains incomplete. Previous studies have revealed genetic (RAS/RTK pathway mutations and TP53 mutations) and phenotypic (monocytic differentiation) resistance mechanisms. In this context, we hypothesized that integrative assessment of both genetic and phenotypic factors could further unveil the contributors of HMA+Ven resistance. To determine the predictors of treatment response, we first analyzed the baseline characteristics of 208 newly diagnosed, secondary, and relapse/refractory AML patients treated with Decitabine and Venetoclax (Dec+Ven). While complex cytogenetics, KRAS and TP53 mutations were significantly associated with treatment resistance, phenotypic factors such as bone marrow cell compositions or French-American-British (FAB) classifications were not. To identify the factors of resistance at the cellular level, we performed a single-cell targeted DNA-antibody sequencing (DAb-seq) on a subset of 33 patients. In total, 60 multi-timepoint bone marrow samples were analyzed, which included five patients with paired baseline-relapse timepoints. From all five patients, we identified that stem-like cells were largely eradicated and replaced by more differentiated cells such as monocyte-like or erythroid-like cells. At relapse, we identified three patterns of phenotypic shifts: monocytic shift, erythroid shift, and mixed monocytic/erythroid shift. The phenotypic shifts were not always associated with the expansion of new genetic mutations, except for in two cases: one patient had monocytic shift accompanied by the expansion of KRAS mutation, and another patient had erythroid shift accompanied by the expansion of NRAS mutation. To examine the mechanisms behind the phenotypic shifts, we performed a single-cell RNA sequencing on three of the relapsed patients. As a result, we confirmed the upregulation of BCL2L1 in the patient with erythroid shift (N=1), and MCL1 in the patients with monocytic shifts (N=2), but not BCL2 in both. These findings are consistent with known dependency of these cells on non-BCL-2 anti-apoptotic proteins such as MCL-1 and BCL-xL. To summarize, we conclude both genetic and phenotypic factors play a role in Dec+Ven resistance. Most importantly, we report that divergent phenotypic transitions, from stem-like toward more differentiated phenotypes (monocytic or erythroid), were frequently observed in AML relapse following Dec+Ven therapy. Close monitoring of phenotypic alterations during HMA+Ven treatment may facilitate the precise identification of AML patients predisposed to relapse. Citation Format: Yi June Kim, Zongrui Li, Abhishek Maiti, Tomoyuki Tanaka, Hidetaka Uryu, Ken Furudate, Kala Hayes, Naval Daver, Naveen Pemmaraju, Tapan M. Kadia, Farhad Ravandi, Nicholas J. Short, Maro Ohanian, Gautam Borthakur, Nitin Jain, Ghayas C. Issa, Lucia Masarova, Steven M. Kornblau, William G. Wierda, Sanam Loghavi, Sa A. Wang, Guillermo Garcia-Manero, Hagop Kantarjian, Courtney D. DiNardo, Marina Y. Konopleva, Koichi Takahashi. Single-cell proteogenomics analysis of AML samples treated with decitabine and venetoclax reveals divergent treatment escape mechanisms [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 3400.

FLAG/FLAG-Ida Regimen in Secondary and Relapsed/Refractory Acute Myeloid Leukemia-Even in the Era of New Treatment Modalities Still a Significant Player.

(1) Background: Relapsed/refractory (r/r) and secondary acute myeloid leukemia are highlighted by chemoresistance and poor outcomes. The aim of the study was to assess the efficacy and toxicity of fludarabine, cytarabine, and granulocyte-colony stimulation factor (FLAG) with or without idarubicin (-Ida) and to discuss novel therapies in this setting. (2) Methods: Clinical and cytogenetic data on 130 consecutive patients with r/r and secondary AML treated at our center were retrospectively analyzed. (3) Results: There were 48, 56, and 26 patients with relapsed, refractory, and secondary AML, respectively. The median age was 60 years. The overall response was achieved in 70% of patients. The median overall survival (OS) time for the whole group was 9.4 months. In total, 47% of patients proceeded to allogeneic hematopoietic stem cell transplantation (aHSCT) and these patients had significantly prolonged OS compared to the others (63 months vs. 4.2 months; p < 0.001). Among the variables, including age, FLT3 mutation status, European LeukemiaNet (ELN) 2022 classification risk, FLAG vs. FLAG-Ida, and aHSCT, a multivariate analysis revealed that only aHSCT significantly influenced overall survival. (4) Conclusions: FLAG(-Ida) chemotherapy remains an effective salvage chemotherapy for patients with r/r and secondary AML with a plan of proceeding to aHSCT.

Abstract 5851: Dysregulated RNA splicing promotes AML quiescence and chemoresistance

Abstract Chemotherapy is the first-line treatment for patients with acute myeloid leukemia (AML). Although most achieve initial remission, an estimated 50% of patients will relapse with poor clinical outcome. The paucity of genetic lesions in AML patients that relapse from chemotherapy implicate non-genetic alterations that mediate chemoresistance. In this study, we conducted a longitudinal analysis of alternative splicing changes in a cohort of 19 AML patients at diagnosis and relapse post-chemotherapy treatment. We found that the long isoform of the transcription factor-encoding gene RUNX1 (also known as RUNX1C) is upregulated in AML relapse cohorts and conferred chemotherapy resistance. Mechanistically, we show that B cell translocation gene 2 (BTG2) is an RUNX1C isoform-specific transcriptional target that promote transition into a quiescent and treatment-resistant state. Direct targeting of RUNX1C mRNA augments chemotherapy response in AML patient-derived xenograft (PDX) models in vivo. These findings uncover an isoform-specific functionality that influences chemotherapy responsiveness and offers a therapeutic strategy to sensitize leukemic cells to conventional chemotherapy treatments. Citation Format: Eric Wang, Cuijuan Han, Alexander Calderon, Abimbo Lawal, Nidhi Hariramani, Edie Crosse, Robert Bradley. Dysregulated RNA splicing promotes AML quiescence and chemoresistance [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 5851.