Which are the most promising targets for minimal residual disease-directed therapy in acute myeloid leukemia prior to allogeneic stem cell transplant?

Molecular, clinical, and prognostic implications of RAS pathway alterations in adult acute myeloid leukemia

Alterations in the RAS pathway underscore the pathogenic complexity of acute myeloid leukemia (AML), yet the full spectrum, including CBL, NF1, PTPN11, KRAS, and NRAS, remains to be fully elucidated. In this retrospective study of 735 adult AML patients, the incidence of RAS pathway alterations was 32.4%, each with distinct clinical characteristics. Venetoclax combined with hypomethylating agents (VEN + HMA) did not significantly improve response rates compared to intensive chemotherapy (IC) group. In the IC group, PTPN11 mutations in the N-SH2 domain showed a trend toward poorer prognosis, though not statistically significant in multivariate analysis, while NRAS mutations correlated with improved outcomes. In the VEN + HMA group, PTPN11 mutations in the N-SH2 domain emerged as an independent adverse prognostic marker. NRAS or KRAS mutations showed no survival advantage compared to wild-type, aligning with their intermediate-risk classification in the 2024 ELN guidelines. These findings emphasize the need for treatment-specific risk stratification for RAS pathway mutations in AML.

Test Then Erase? Current Status and Future Opportunities for Measurable Residual Disease Testing in Acute Myeloid Leukemia

BACKGROUND

Measurable residual disease (MRD) test positivity during and after treatment in patients with acute myeloid leukemia (AML) has been associated with higher rates of relapse and worse overall survival. Current approaches for MRD testing are not standardized leading to inconsistent results and poor prognostication of disease. Pertinent studies evaluating AML MRD testing at specific times points, with various therapeutics and testing methods are presented.

SUMMARY

AML is a set of diseases with different molecular and cytogenetic characteristics and is often polyclonal with evolution over time. This genetic diversity poses a great challenge for a single AML MRD testing approach. The current ELN 2021 MRD guidelines recommend MRD testing by quantitative polymerase chain reaction in those with a validated molecular target or multiparameter flow cytometry (MFC) in all other cases. The benefit of MFC is the ability to use this method across disease subsets, at the relative expense of suboptimal sensitivity and specificity. AML MRD detection may be improved with molecular methods. Genetic characterization at AML diagnosis and relapse is now standard of care for appropriate therapeutic assignment, and future initiatives will provide the evidence to support testing in remission to direct clinical interventions.

KEY MESSAGES

The treatment options for patients with AML have expanded for specific molecular subsets such as FLT3 and IDH1/2 mutated AML, with development of novel agents for NPM1 mutated or KMT2A rearranged AML ongoing, but also due to effective venetoclax-combinations. Evidence regarding highly sensitive molecular MRD detection methods for specific molecular subgroups, in the context of these new treatment approaches, will likely shape the future of AML care.

Targeting acute myeloid cell surface using a recombinant antibody isolated from whole-cell biopanning of a phage display human scFv antibody library

To discover new therapeutic antibodies for treatment of acute myeloid leukemia (AML) without the requirement of a known antigen, a human single-chain variable fragment (scFv) library was used to isolate novel antibody fragments recognizing HL-60 AML cells. After three rounds of biopanning, scFv-expressing phages were selected to test for binding to the target cell by flow cytometry. The clone with highest binding specificity to HL-60 cells (designated y1HL63D6) was further investigated. Fluorescent staining indicated that y1HL63D6 scFv bound to a target located on the cell surface. Whole immunoglobulin, IgG-y1HL63D6 was then generated and tested for the binding against bone marrow mononuclear cells (BMMCs) from AML patients. Significantly higher fluorescent signals were observed for some patient samples when compared to normal BMMCs or non-AML patients' BMMCs. Next, the IgG-y1HL63D6 format was tested for antibody-dependent cell cytotoxicity (ADCC). The results demonstrated that IgG-y1HL63D6 but not the control antibody, trastuzumab, could mediate specific killing of HL-60 target cells. In conclusion, our results indicate that specific antibodies can be isolated by biopanning whole cells with a non-immunized human scFv antibody phage display library and that the isolated antibody against HL-60 cells showed therapeutic potential.

The pyroptosis-related gene signature predicts prognosis and reveals characterization of the tumor immune microenvironment in acute myeloid leukemia

Background: Pyroptosis is a novel inflammatory form of programmed cell death and a prospective target for cancer therapy. Nevertheless, little is known about the association between pyroptosis-related genes (PRGs) and acute myeloid leukemia (AML) prognosis. Herein, we systematically investigated the specific functions and clinical prognostic value of multiple PRGs in AML.

Methods: Univariate and LASSO Cox regression analyses based on TCGA and GTEx databases were used to generate the PRG signature, whose predictive efficacy of survival was evaluated using survival analysis, ROC, univariate and multivariate Cox analyses as well as subgroup analysis. The BeatAML cohort was used for data validation. The association between risk score and immune cell infiltration, HLA, immune checkpoints, cancer stem cell (CSC), tumor mutation burden (TMB), and therapeutic drug sensitivity were also analyzed.

Results: Six -PRG signatures, namely, CASP3, ELANE, GSDMA, NOD1, PYCARD, and VDR were generated. The high-risk score represented a poorer prognosis and the PRG risk score was also validated as an independent predictor of prognosis. A nomogram including the cytogenetic risk, age, and risk score was constructed for accurate prediction of 1-, 3-, and 5-year survival probabilities. Meanwhile, this risk score was significantly associated with the tumor immune microenvironment (TIME). A high-risk score is characterized by high immune cell infiltration, HLA, and immune checkpoints, as well as low CSC and TMB. In addition, patients with low-risk scores presented significantly lower IC50 values for ATRA, cytarabine, midostaurin, doxorubicin, and etoposide.

Conclusion: Our findings might contribute to further understanding of PRGs in the prognosis and development of AML and provide novel and reliable biomarkers for its precise prevention and treatment.

Clinical Impact of Measurable Residual Disease in Acute Myeloid Leukemia

Simple Summary

Advances in immunophenotyping and molecular techniques have allowed for the development of more sensitive diagnostic tests in acute leukemia. These techniques can identify low levels of leukemic cells (quantified as 10⁻⁴ to 10⁻⁶ ratio to white blood cells) in patient samples. The presence of such low levels of leukemic cells, termed “measurable/minimal residual disease” (MRD), has been shown to be a marker of disease burden and patient outcomes. In acute lymphoblastic leukemia, new agents are highly effective at eliminating MRD for patients whose leukemia progressed despite first line therapies. By comparison, the role of MRD in acute myeloid leukemia is less clear. This commentary reviews select data and remaining questions about the clinical application of MRD to the treatment of patients with acute myeloid leukemia.

Abstract

Measurable residual disease (MRD) has emerged as a primary marker of risk severity and prognosis in acute myeloid leukemia (AML). There is, however, ongoing debate about MRD-based surveillance and treatment. A literature review was performed using the PubMed database with the keywords MRD or residual disease in recently published journals. Identified articles describe the prognostic value of pre-transplant MRD and suggest optimal timing and techniques to quantify MRD. Several studies address the implications of MRD on treatment selection and hematopoietic stem cell transplant, including patient candidacy, conditioning regimen, and transplant type. More prospective, randomized studies are needed to guide the application of MRD in the treatment of AML, particularly in transplant.

Clinical implications of combination therapy with quizartinib and craniospinal irradiation for refractory acute myeloid leukemia positive for FMS-like tyrosine kinase 3-internal tandem duplication with central nervous system involvement

FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) mutation-positive acute myeloid leukemia (AML) has a poor prognosis. We report the first case of successful bridge therapy of novel FLT3 inhibitor, quizartinib, to umbilical cord blood stem cell transplantation for FLT3-ITD-positive AML-primary induction failure patients with central nervous system involvement.

Revealing the Mysteries of Acute Myeloid Leukemia: From Quantitative PCR through Next-Generation Sequencing and Systemic Metabolomic Profiling

The efforts made in the last decade regarding the molecular landscape of acute myeloid leukemia (AML) have created the possibility of obtaining patients’ personalized treatment. Indeed, the improvement of accurate diagnosis and precise assessment of minimal residual disease (MRD) increased the number of new markers suitable for novel and targeted therapies. This progress was obtained thanks to the development of molecular techniques starting with real-time quantitative PCR (Rt-qPCR) passing through digital droplet PCR (ddPCR) and next-generation sequencing (NGS) up to the new attractive metabolomic approach. The objective of this surge in technological advances is a better delineation of AML clonal heterogeneity, monitoring patients without disease-specific mutation and designing customized post-remission strategies based on MRD assessment. In this context, metabolomics, which pertains to overall small molecules profiling, emerged as relevant access for risk stratification and targeted therapies improvement. In this review, we performed a detailed overview of the most popular modern methods used in hematological laboratories, pointing out their vital importance for MRD monitoring in order to improve overall survival, early detection of possible relapses and treatment efficacy.

Advances in acute myeloid leukemia

Acute myeloid leukemia (AML) is an uncommon but potentially catastrophic diagnosis with historically high mortality rates. The standard of care treatment remained unchanged for decades; however, recent discoveries of molecular drivers of leukemogenesis and disease progression have led to novel therapies for AML. Ongoing research and clinical trials are actively seeking to personalize therapy by identifying molecular targets, discovering patient specific and disease specific risk factors, and identifying effective combinations of modalities and drugs. This review focuses on important updates in diagnostic and disease classifications that reflect new understanding of the biology of AML, its mutational heterogeneity, some important genetic and environmental risk factors, and new treatment options including cytotoxic chemotherapy, novel targeted agents, and cellular therapies.

Venetoclax-based combinations for the treatment of newly diagnosed acute myeloid leukemia

Elderly and/or unfit patients with acute myeloid leukemia have historically been challenging to manage as they were ineligible for what was considered standard of care treatment with induction chemotherapy. The emergence of venetoclax with hypomethylating agents or low-dose cytarabine has substantially improved outcomes in the frontline setting with manageable toxicity. However, this regimen can be challenging to deliver given its differences from standard intensive chemotherapy. In this review, we summarize the landmark trials that established venetoclax-based combinations as a new standard of care for patients with acute myeloid leukemia not suitable for intense chemotherapy, provide practical clinical pearls for managing patients on these therapies, and offer a brief overview of modifications to these regimens under development to improve their efficacy and/or applicability.

Current and Emerging Therapies for Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is predominantly a disease of older adults and the majority of affected patients succumb to the disease. After decades of slow progress, the last 5 years have witnessed remarkable progress in AML therapy with the approval of multiple highly active and well-tolerated novel therapies. Notable among these are agents targeting driver mutations including FLT3, IDH1/2 as well as the Bcl-2 inhibitor venetoclax. The combination of hypomethylating agents with venetoclax is highly active in AML and has become the standard of care for older patients as well as those with comorbidities. As a result of these advances, a larger proportion of AML patients now achieve complete remissions enabling them to undergo allogeneic hematopoietic cell transplantation with curative intent. Progress is also being made in the field of monoclonal antibodies targeting leukemia antigens and other immunotherapies and many such agents are currently under active investigation.

Natural killer cell-based immunotherapy for acute myeloid leukemia

Despite considerable progress has been achieved in the treatment of acute myeloid leukemia over the past decades, relapse remains a major problem. Novel therapeutic options aimed at attaining minimal residual disease-negative complete remission are expected to reduce the incidence of relapse and prolong survival. Natural killer cell-based immunotherapy is put forward as an option to tackle the unmet clinical needs. There have been an increasing number of therapeutic dimensions ranging from adoptive NK cell transfer, chimeric antigen receptor-modified NK cells, antibodies, cytokines to immunomodulatory drugs. In this review, we will summarize different forms of NK cell-based immunotherapy for AML based on preclinical investigations and clinical trials.

Current strategies for detection and approach to measurable residual disease in acute myeloid leukemia

Baseline cytogenetic/genetic features have been widely recognized to play a critical prognostic role in acute myeloid leukemia (AML) and have proven useful in designing risk-adapted treatment strategies. Nevertheless, to improve further the outcome of AML patients we are still in need of accurate methods to explore the quality of response and to adequately discriminate patients who are likely to relapse over time from those who are in deep and stable remission. In this view, is it well established that measurement of leukemic cells surviving chemotherapy (called measurable residual disease, MRD) during the course of treatment may be a reliable biomarker in predicting relapse. Detection of MRD relies on highly sensitive techniques, such as quantitative polymerase chain reaction and multiparametric flow cytometry, which, due to their levels of specificity and sensitivity, are increasingly included in the decision-making process of AML treatment. In the present manuscript, we will review the current techniques of MRD investigation and their clinical contribution to AML management.

Biomarkers of Gemtuzumab Ozogamicin Response for Acute Myeloid Leukemia Treatment

Gemtuzumab ozogamicin (GO, Mylotarg®) consists of a humanized CD33-targeted antibody-drug conjugated to a calicheamicin derivative. Growing evidence of GO efficacy in acute myeloid leukemia (AML), demonstrated by improved outcomes in CD33-positive AML patients across phase I to III clinical trials, led to the Food and Drug Administration (FDA) approval on 1 September 2017 in CD33-positive AML patients aged 2 years and older. Discrepancies in GO recipients outcome have raised significant efforts to characterize biomarkers predictive of GO response and have refined the subset of patients that may strongly benefit from GO. Among them, CD33 expression levels, favorable cytogenetics (t(8;21), inv(16)/t(16;16), t(15;17)) and molecular alterations, such as NPM1, FLT3-internal tandem duplications and other signaling mutations, represent well-known candidates. Additionally, in depth analyses including minimal residual disease monitoring, stemness expression (LSC17 score), mutations or single nucleotide polymorphisms in GO pathway genes (CD33, ABCB1) and molecular-derived scores, such as the recently set up CD33_PGx6_Score, represent promising markers to enhance GO response prediction and improve patient management.

The Progression of Acute Myeloid Leukemia from First Diagnosis to Chemoresistant Relapse: A Comparison of Proteomic and Phosphoproteomic Profiles

Acute myeloid leukemia (AML) is an aggressive hematological malignancy. Nearly 50% of the patients who receive the most intensive treatment develop chemoresistant leukemia relapse. Although the leukemogenic events leading to relapse seem to differ between patients (i.e., regrowth from a clone detected at first diagnosis, progression from the original leukemic or preleukemic stem cells), a common characteristic of relapsed AML is increased chemoresistance. The aim of the present study was to investigate at the proteomic level whether leukemic cells from relapsed patients present overlapping molecular mechanisms that contribute to this chemoresistance. We used liquid chromatography–tandem mass spectrometry (LC–MS/MS) to compare the proteomic and phosphoproteomic profiles of AML cells derived from seven patients at the time of first diagnosis and at first relapse. At the time of first relapse, AML cells were characterized by increased levels of proteins important for various mitochondrial functions, such as mitochondrial ribosomal subunit proteins (MRPL21, MRPS37) and proteins for RNA processing (DHX37, RNA helicase; RPP40, ribonuclease P component), DNA repair (ERCC3, DNA repair factor IIH helicase; GTF2F1, general transcription factor), and cyclin-dependent kinase (CDK) activity. The levels of several cytoskeletal proteins (MYH14/MYL6/MYL12A, myosin chains; VCL, vinculin) as well as of proteins involved in vesicular trafficking/secretion and cell adhesion (ITGAX, integrin alpha-X; CD36, platelet glycoprotein 4; SLC2A3, solute carrier family 2) were decreased in relapsed cells. Our study introduces new targetable proteins that might direct therapeutic strategies to decrease chemoresistance in relapsed AML.

Synergistic Anti Leukemia Effect of a Novel Hsp90 and a Pan Cyclin Dependent Kinase Inhibitors

Acute myeloid leukemia (AML) is among the top four malignancies in Saudi nationals, and it is the top leukemia subtype worldwide. Resistance to available AML drugs requires the identification of new targets and agents. Hsp90 is one of the emerging important targets in AML, which has a central role in the regulation of apoptosis and cell proliferation through client proteins including the growth factor receptors and cyclin dependent kinases. The objective of the first part of this study is to investigate the putative Hsp90 inhibition activity of three novel previously synthesized quinazolines, which showed HL60 cytotoxicity and VEGFR2 and EGFR kinases inhibition activities. Using surface plasmon resonance, compound 1 (HAA₂₀₂₀) showed better Hsp90 inhibition compared to 17-AAG, and a docking study revealed that it fits nicely into the ATPase site. The objective of the second part is to maximize the anti-leukemic activity of HAA₂₀₂₀, which was combined with each of the eleven standard inhibitors. The best resulting synergistic effect in HL60 cells was with the pan cyclin-dependent kinases (CDK) inhibitor dinaciclib, using an MTT assay. Furthermore, the inhibiting effect of the Hsp90α gene by the combination of HAA₂₀₂₀ and dinaciclib was associated with increased caspase-7 and TNF-α, leading to apoptosis in HL60 cells. In addition, the combination upregulated p27 simultaneously with the inhibition of cyclinD3 and CDK2, leading to abolished HL60 proliferation and survival. The actions of HAA₂₀₂₀ propagated the apoptotic and cell cycle control properties of dinaciclib, showing the importance of co-targeting Hsp90 and CDK, which could lead to the better management of leukemia.

CD123 as a Therapeutic Target in the Treatment of Hematological Malignancies

The interleukin-3 receptor alpha chain (IL-3Rα), more commonly referred to as CD123, is widely overexpressed in various hematological malignancies, including acute myeloid leukemia (AML), B-cell acute lymphoblastic leukemia, hairy cell leukemia, Hodgkin lymphoma and particularly, blastic plasmacytoid dendritic neoplasm (BPDCN). Importantly, CD123 is expressed at both the level of leukemic stem cells (LSCs) and more differentiated leukemic blasts, which makes CD123 an attractive therapeutic target. Various agents have been developed as drugs able to target CD123 on malignant leukemic cells and on the normal counterpart. Tagraxofusp (SL401, Stemline Therapeutics), a recombinant protein composed of a truncated diphtheria toxin payload fused to IL-3, was approved for use in patients with BPDCN in December of 2018 and showed some clinical activity in AML. Different monoclonal antibodies directed against CD123 are under evaluation as antileukemic drugs, showing promising results either for the treatment of AML minimal residual disease or of relapsing/refractory AML or BPDCN. Finally, recent studies are exploring T cell expressing CD123 chimeric antigen receptor-modified T-cells (CAR T) as a new immunotherapy for the treatment of refractory/relapsing AML and BPDCN. In December of 2018, MB-102 CD123 CAR T developed by Mustang Bio Inc. received the Orphan Drug Designation for the treatment of BPDCN. In conclusion, these recent studies strongly support CD123 as an important therapeutic target for the treatment of BPDCN, while a possible in the treatment of AML and other hematological malignancies will have to be evaluated by in the ongoing clinical studies.