Search Results (72)

Acute myeloid leukemia (AML) is a highly aggressive malignancy defined by significant biological diversity and variable patient outcomes. A key subset of AML is driven by abnormalities that lead to the overexpression of the oncogenic transcription factors HOXA9 and MEIS1. These abnormalities include KMT2A (formerly MLL) rearrangements and NPM1 mutations, as well as other rare lesions such as NUP98 rearrangements. This review focuses on the biology of the KMT2A, NPM1, and HOX/MEIS1 pathways, dissecting their molecular mechanisms of leukemogenesis. A central theme is the role of the scaffolding protein menin in the epigenetic regulation of this pathway, which ultimately drives malignant transformation. Currently, the clinical landscape is being transformed by the emergence of menin inhibitors as promising therapeutic agents for AML harboring these specific genetic anomalies. We evaluate the latest data on various menin inhibitors—both as monotherapy and in combinations—emphasizing their efficacy and safety profiles. As new evidence continues to accumulate with recent drug approvals and ongoing randomized, phase 3 studies, menin inhibitors are rapidly becoming a component of the AML treatment paradigm for relapsed/refractory and likely newly diagnosed disease. Full article

Background: The KMT2A (MLL1) gene is altered in a variety of hematological malignancies and solid tumors. KMT2A-rearranged (KMT2Ar) AML represents a distinct subtype associated with poor outcomes and high relapse rate despite initial responsiveness to chemotherapy. Methods: A total of 3863 cases of AML peripheral blood samples were analyzed using the FoundationOne Heme combined comprehensive hybrid capture-based DNA and RNA sequencing assay. Results: Of the 3863 AML cases, 521 (13.4%) featured genomic alterations (GAs) in the KMT2A gene, 99.1% of which were large rearrangements (KMT2Ar). A total of 56.9% were males with a median age of 62 years. Of the KMT2Ar cases, there were 43.1% KMT2A duplications, 52.7% fusions, and 4.2% not otherwise specified rearrangements. A total of 0.9% of the KMT2A-altered AML cases were short variant mutations. There were no KMT2A (0%) amplifications or deletions. KMT2Ar cases were associated with increased GA frequencies in FLT3 (27.3% vs. 19.8%; p = 0.0002), KRAS (17.2% vs. 7.8%; p < 0.0001) (overall; 1.1% KRAS G12C), and IDH2 (16.0% vs. 10.4%; p < 0.0001), while KMT2A wild-type AML (KMT2Awt) had significantly increased GA frequencies in RUNX1 (20.7% vs. 15.8%; p = 0.0081), ASXL1 (16.6% vs. 10.5%; p = 0.0003), and TET2 (16.4% vs. 10.1%; p = 0.0002), NPM1 (17.5% vs. 0.2%; p < 0.0001), and TP53 (17.8% vs. 7.9%; p < 0.0001). Conclusions: KMT2A rearrangements are common in AML (13.4% of cases featured KMT2Ar). A total of 99.1% of alterations in KMT2A are large rearrangements, with fusions being the most commonly observed alteration (52.7% of total rearrangements). No amplifications or deletions were seen. This genomic landscape study highlights significant genomic differences between KMT2Ar and KMT2Awt AML patients, which may enrich our understanding of the molecular profile and clusters of mutations in AML. Full article

Nodal marginal zone lymphoma (NMZL) is an indolent B-cell lymphoma that may pose diagnostic challenges due to the absence of distinct markers. In rare atypical cases, an overabundance of PD1+ T follicular helper (TFH) cells in tumor tissue may mimic peripheral T-cell lymphoma (PTCL) of TFH origin, further complicating the diagnosis. A 72-year-old woman with progressive lymphadenopathy had a cervical lymph node biopsy showing a disrupted architecture with monomorphic nodules of CD20+/MNDA+ B-cells and a prominent central population of proliferating CD4+/PD1+ T-cells, initially suggestive of a PTCL-TFH. The bone marrow contained aggregates of CD20+ B-cells intermixed with CD3+/CD4+/PD1+ T-cells. Next-generation sequencing (NGS) revealed clonal immunoglobulin heavy-chain rearrangements in the lymph node and bone marrow, with T-cell receptor genes displaying a polyclonal pattern. Targeted NGS showed no PTCL-related alterations but identified NMZL-associated mutations with different distributions across lymph node and bone marrow compartments. NOTCH2 mutations (c.6418C>T; p.Gln2140*) were found in both tissues, while the (c.69+2T>A; p.?) TNFRSF14 gene mutation was only detected in the lymph node. The KMT2D gene displayed a frameshift variant in the lymph node (c.4801_4802delinsT; p.Arg1601Leufs*3) and an in-frame deletion (c.11756_11758del; p.Gln3919del) in the bone marrow. Notably, NGS and digital droplet PCR confirmed a TP53 frameshift mutation (c.902del; p.Pro301Glnfs*44) with a fractional abundance of 0.31% in the lymph node and a (c.742C>T; p.Arg248Trp) mutation (0.309%) in the bone marrow. Results underscore the importance of NGS-based clonality to diagnose NMZL with prominent PD1+ T-cell hyperplasia, and prompt further investigation into tissue-specific mutational signatures in these unusual cases. Full article

KMT2A-rearranged (KMT2A-r) acute lymphoblastic leukemia (ALL), particularly in infants, represents one of the most aggressive pediatric hematological malignancies with a historically dismal prognosis. While KMT2A-AFF1 (t(4;11)) is the most prevalent fusion, a diverse array of partner genes exists, each conferring distinct biological and clinical features. This review focuses on the rare but clinically significant KMT2A-AFF3 subtype, which arises from the t(2;11)(q11.2;q23) chromosomal translocation. This review summarizes the molecular pathogenesis driven by the KMT2A-AFF3 fusion oncoprotein, which functions as an aberrant transcriptional complex. This complex hijacks essential epigenetic machinery, including the recruitment of DOT1L and interaction with Menin, leading to pathogenic histone modifications (e.g., H3K79 hypermethylation) and the subsequent upregulation of critical target genes, notably the HOXA cluster and MEIS1, thereby enforcing a B-lymphoid differentiation arrest at the pro-B/pre-B stage. Clinically, KMT2A-AFF3 ALL is characterized by high-risk features, including infant onset, hyperleukocytosis, central nervous system (CNS) involvement, and a distinct CD10-negative immunophenotype. This review highlights the evidence defining its poor prognosis, which is primarily driven by profound chemoresistance to conventional therapies, including glucocorticoids. Finally, we discuss the rapidly evolving therapeutic landscape, detailing the limitations of standard intensive chemotherapy and the immense promise of novel targeted strategies, such as Menin inhibitors (e.g., Revumenib), DOT1L inhibitors, and immunotherapies (e.g., CAR-T cells, Blinatumomab), which hold the potential to revolutionize outcomes for this high-risk leukemia subtype. Full article

Background: Pediatric acute myeloid leukemia (pAML) is the second most common type of childhood leukemia, behind acute lymphoblastic leukemia. High-throughput technologies have enabled the identification of increasing molecular alterations linked to AML prognosis, revealing genomic heterogeneity among individual patients and providing clinically valuable diagnostic and prognostic information. This study systematically analyzed the correlation between high-frequency mutated genes and prognosis in pAML by performing whole-transcriptome sequencing (WTS) of bone marrow samples from newly diagnosed AML children in Southwest China and mapping their genetic profiles. Methods: pAML patients treated at the Department of Hematology and Oncology, Children’s Hospital of Chongqing Medical University, from January 2015 to October 2024, were enrolled, and WTS was performed. The study described the frequency, pathogenicity classification, and risk stratification of mutation genes and fusion genes, and constructed a genetic landscape. For high-frequency pAML mutations, the impact on early induction remission rate (CR) and long-term event-free survival (EFS) was evaluated. Results: A total of 134 pediatric AML patients from Southwest China were included, with a male-to-female ratio of 74:60 and a median diagnosis age of 5.96 years. Based on pathogenicity classification using WTS, fusion genes were categorized into level 1, level 2, and level 3 genes, as well as mutation genes. The study identified five fusion genes of level 1, the most frequent being RUNX1::RUNX1T1 (32/134, 23.88%), KMT2A rearrangements (29/134, 21.64%), and CBFB::MYH11 (13/134, 9.7%). Sixteen mutation genes of level 1 were detected, seven of which recurred in over 5% of patients, including NRAS (31/134, 23.13%), FLT3 (25/134, 18.66%), KIT (24/134, 17.91%), CEBPA (14/134, 10.45%), WT1 (13/134, 9.7%), KRAS (11/134, 8.2%), and PTPN11 (7/134, 5.22%). Sex-based analysis revealed that PTPN11 mutations were significantly more frequent in males (9.45% vs. 0%, p = 0.023), as were KIT mutations (24.32% vs. 10.00%, p = 0.044). Risk-stratified analysis showed that WT1 mutations (14.13% vs. 0%, p = 0.031) and FLT3-ITD mutations (13.19% vs. 0%, p = 0.042) were enriched in intermediate- and high-risk groups, whereas CEBPA (25.64% vs. 5.43%, p = 0.012), KIT (35.90% vs. 10.87%, p = 0.003), and KIT-E8 (20.51% vs. 1.10%, p < 0.001) mutations were more prevalent in low-risk groups. Prognostic analysis indicated that PTPN11 and KIT mutations did not affect CR or EFS across sexes, nor did WT1, CEBPA, or KIT mutations influence outcomes by risk stratification. However, FLT3-ITD-positive patients had significantly lower CRs (χ² value = 11.965, p = 0.007), although EFS differences were nonsignificant. In contrast, WT1 mutations were associated with inferior EFS compared to wild-type (p = 0.036). Furthermore, the univariate and multivariate Cox regression revealed consistent results with the above findings, indicating that WT1 mutation was an independent adverse prognostic factor for EFS (HR = 2.400, 95% CI: 1.101–5.233, p = 0.028). The results of univariate and multivariate logistic regression analyses also confirmed that FLT3-ITD mutation was an independent predictor of initial treatment response in our cohort (OR = 10.699, 95% CI: 2.108–54.302, p = 0.004). Conclusions: This study delineated the genetic landscape of pAML in Southwest China and explored the prognostic value of gene fusions and mutations in early and long-term outcomes. These findings provide a foundation for understanding the genetic heterogeneity of pAML and offer evidence for the development of precision medicine approaches. Full article

Background: Acute lymphoblastic leukemia (ALL) is a genetically heterogeneous malignancy driven by structural variants (SVs) that impact diagnosis, prognosis, and treatment. Traditional methods such as karyotyping, FISH, and PCR often fail to detect cryptic or complex rearrangements, which are critical for accurate risk stratification. Methods: Optical Genome Mapping (OGM) is a technology that directly analyzes ultra-high-molecular-weight DNA, enabling the identification of balanced and unbalanced SVs, copy number variations (CNVs), and gene fusions with high resolution. This review compares the advantages and limitations of OGM versus standard techniques in ALL. Results: OGM improves ALL diagnosis by detecting clinically relevant alterations such as IKZF1 deletions, cryptic KMT2A rearrangements, and kinase fusions, especially in cases with normal or uninformative karyotypes. It reduces artifacts by eliminating cell culture and shortens reporting times. OGM resolves complex events like intrachromosomal amplifications and chromothripsis, enhancing classification and therapy decisions. Limitations include reduced sensitivity in repetitive regions, challenges in detecting Robertsonian translocations, difficulties with complex ploidies, and lower sensitivity for low-frequency subclones. Conclusions: Integrating OGM with next-generation sequencing (NGS) allows comprehensive genomic profiling, improving diagnosis, prognosis, and personalized treatment in ALL. Future advancements promise to further enhance the clinical utility of OGM. Full article

Background: Angioimmunoblastic T-cell lymphoma (AITL) and peripheral T-cell lymphomas (PTCL), not otherwise specified (NOS), share overlapping histology and T-follicular helper (TFH) biology but often show divergent outcomes and treatment needs. The clinical significance of KMT2A rearrangement (KMT2A-r) in nodal PTCL remains undefined. We aimed to investigate the clinicogenomic features and prognostic impact of KMT2A-r in AITL and PTCL-NOS. Methods: We retrospectively analyzed consecutive patients diagnosed with AITL or PTCL-NOS between 2021 and 2024 at two centers. All patients underwent 523-gene DNA/RNA next-generation sequencing. Gene co-variation and diagnostic splits were summarized using network and decision-tree analyses. Results: Overall, 37 patients were included (AITL: 14; PTCL-NOS: 23), with similar baseline clinical characteristics. In AITL, TFH markers were more frequently expressed, and RHOA mutations were enriched. KMT2A-r occurred in 24% of cases without histology-specific enrichment. AITL showed better 2-year overall survival (OS) than PTCL-NOS (70.7% vs. 38.8%; p = 0.040) but similar progression-free survival (PFS). Univariate analysis revealed that KMT2A-r, lactate dehydrogenase elevation, and bone-marrow involvement predicted inferior PFS (Hazard ratio for KMT2A-r: 2.56). Median PFS was 5.9 versus 12.5 months in the KMT2A-r and non-KMT2A-r groups, respectively (p = 0.039). Brentuximab vedotin (BV) plus cyclophosphamide, doxorubicin, and prednisone did not significantly improve OS or PFS overall; however, exploratory analysis indicated improved PFS in the KMT2A-r subset. Conclusions: KMT2A-r delineates an adverse-risk biology in nodal PTCL, aligns with non-TFH genomic hubs and markers of tumor burden, and may serve as a stratifier and hypothesis-generating target for BV-based strategies. Full article

Background/Objectives: Relapsed acute myeloid leukemia (AML) is often characterized by clonal evolution and acquired genomic abnormalities, which can inform prognosis and direct therapeutic decisions. The emergence of high-risk chromosomal rearrangements during relapse is of particular significance, yet the impact of rare and complex events remains poorly understood. This report details a case of relapsed AML that demonstrated rare MYC and MECOM rearrangements and additional features that were not observed at initial diagnosis, emphasizing the clinical relevance of serial cytogenetic assessments. Case Description: A 70-year-old man was initially diagnosed with AML, exhibiting monocytic differentiation, an 11q23 deletion involving KMT2A loss, and a U2AF1 mutation. After achieving remission with azacitidine and venetoclax, the patient relapsed within ten months, necessitating reevaluation and modification of therapy. Repeat cytogenetic analysis at relapse revealed a distinct t(3;8)(q26.2;q24.3) exhibiting MYC and MECOM rearrangements, features that were absent at initial diagnosis. Conclusions: This case underscores the importance of serial cytogenetic and molecular profiling in relapsed AML. The emergence of new abnormalities upon relapse suggested underlying genomic instability and clonal evolution. MYC rearrangements are notably rare in AML, especially with concurrent MECOM rearrangements, highlighting a unique feature of this case. The identification of novel abnormalities at relapse may carry prognostic and therapeutic significance and may be used to refine risk stratification. Thus, ongoing cytogenetic monitoring is essential to adapt management approaches in evolving disease contexts. Full article

Background/Objectives: Fluorescence in situ hybridization (FISH) is a standard diagnostic tool for detecting gene fusions and rearrangements in lymphomas but is limited by incomplete genomic coverage, dependence on predefined probes, and difficulty identifying atypical or noncanonical fusion partners. These constraints often result in inconclusive diagnoses in complex lymphoma cases. This study evaluates a novel Hi-C-based sequencing assay from formalin-fixed paraffin-embedded (FFPE) samples to detect clinically significant gene fusions and rearrangements in cases where conventional FISH was inconclusive or expected biomarkers were not detected. Methods: Five diffuse large B-cell lymphoma cases with previously atypical gene fusions or rearrangements by FISH were analyzed using both standard FISH and a Hi-C-based lymphoma assay. Standard FISH was performed using break-apart probes targeting MYC, BCL2, and BCL6, and dual-fusion probes targeting IGH::MYC and IGH::BCL2. The Hi-C assay utilized high-resolution sequencing of FFPE tissue to map chromatin interactions and identify structural variations across the genome and assessment of their clinical relevance. Results: In this series of five lymphoma cases, Hi-C detected additional structural variants beyond those identified by FISH. It identified typical and atypical translocation partners of key oncogenes (MYC, BCL2, BCL6), cryptic breakpoints, and novel genomic events, including TP53 loss, KMT2A amplification, and complex rearrangements, which were undetectable by FISH. The Hi-C assay’s whole-genome coverage enabled comprehensive profiling. Conclusions: The Hi-C-based lymphoma assay offers a transformative diagnostic tool, overcoming FISH limitations by providing unbiased, high-resolution detection of structural variations. This approach enhances diagnostic accuracy and supports personalized therapeutic strategies in lymphoma management, warranting further validation for clinical adoption. Full article

The development of molecular profiling approaches for AML patients such as whole genome sequencing, whole exome sequencing and transcriptomic sequencing have greatly contributed to better understanding of leukemia development, progression and treatment responsiveness/resistance. These studies have generated a new knowledge about driver events operating in AML that can be translated into clinics, thus favoring the mutations; using this approach, more than 50% of older AML patients display molecular alterations, such as IDH1, IDH2, FLT3 (FLT3-TKD and FLT3-ITD), NPM1 and KMT2A rearrangements that can be targeted by specific drugs. Preclinical and clinical studies have supported the use of drugs targeting these molecular alterations as first-line therapy in association with induction chemotherapy in chemotherapy-fit patients or with a hypomethylating agent in association with a Bcl-2 inhibitor (Venetoclax) in chemotherapy-unfit patients. These studies have shown promising results that need to be confirmed through randomized clinical studies specifically involving the enrollment of older AML patients. Full article

Menin inhibitors are a class of targeted agents that exemplify how a deeper understanding of leukemia pathogenesis can unify seemingly distinct genetic acute leukemia subgroups under a common therapeutic strategy. In particular, acute leukemia with NPM1 mutations (NPM1m) and KMT2A rearrangements (KMT2Ar) represent the primary targets of this emerging drug class. Acute myeloid leukemia (AML) with NPM1m—which accounts for approximately 30% of AML cases and AML or acute lymphoblastic leukemia (ALL) with KMT2Ar—and is present in 5–10% of cases, shares a common pathogenetic mechanism: the aberrant activation of the MEIS1–HOXA axis. These leukemic subsets are associated with poor prognosis, particularly in the relapsed/refractory (R/R) setting. For KMT2Ar AML, the prognosis is especially dismal, with a median overall survival (OS) of 2.4 months and a complete remission (CR) rate of only 5%. In NPM1m AML, intensive chemotherapy achieves remission in approximately 80% of cases, but relapse remains a major challenge, occurring in nearly 50% of patients. Relapsed NPM1m AML is linked to a poor prognosis, with a median OS of 6.1 months (12-month OS: 30%) and a median relapse-free survival (RFS) of 5.5 months (12-month RFS: 34%). Menin inhibitors directly target the leukemogenic transcriptional program driven by HOX and MEIS1, disrupting oncogenic signaling and offering a promising therapeutic approach for these high-risk patients. This class of agents has rapidly progressed through clinical development, showing promising antileukemic activity in both treatment-naïve and R/R AML. Currently, six menin inhibitors are in clinical evaluation as monotherapy or in combination regimens: revumenib, ziftomenib, bleximenib (previously JNJ-75276617), enzomenib (previously DSP-5336), DS-1594, and BMF-219. In this review, we critically analyze the clinical development and therapeutic potential of the four most extensively studied menin inhibitors—revumenib, ziftomenib, bleximenib, and enzomenib. We discuss their efficacy, safety profiles, and potential roles within the current treatment algorithm. The continued clinical evaluation of menin inhibitors may redefine treatment paradigms for NPM1m and KMT2Ar AML and other acute leukemia with the aberrant MEIS1-HOXA axis, offering new hope for patients with limited therapeutic options. Full article

Background/Objectives: Magrolimab (Magro) is a humanized naked anti-CD47 monoclonal antibody that blocks the SIRPα CD47 interaction, allowing macrophages to target and destroy cancer cells. To evaluate its preclinical efficacy in vivo, Magro was tested as a single agent and in combination with conventional chemotherapy drugs, Cytarabine (Ara-C) or Azacitidine (Aza), in three pediatric AML (pAML) patient-derived xenograft (PDX) models—AML006 (KMT2A::MLLT1), AML010 (+10, WT1), and AML013 (KMT2A::MLLT4). Methods: After PDX model establishment, mice were assigned to treatment groups hulgG4 (VC, vehicle control for Magro), Magro, Ara-C + VC, Aza + VC, Ara-C + Magro, and Aza + Magro, and then followed for survival. Mice that met humane euthanasia endpoints and at the culmination of experimental timelines had tissues harvested to measure disease burden. Results: Magro alone significantly improved survival in AML006 (p < 0.0001) and AML013 (p = 0.003) and decreased bone marrow (BM) disease burden in AML006 (p = 0.009) and AML013 (p = 0.002). Ara-C + Magro therapy led to significantly improved survival in all three models and significantly decreased BM disease burden in AML006 (p < 0.0001) and AML013 (p = 0.048). Aza + Magro therapy led to significantly improved survival in AML013 (p = 0.047) and AML010 (p = 0.017) and significantly lower BM disease burden in AML010 (p = 0.001). Conclusions: Interestingly, the two models that demonstrated improvement in survival with Magro harbored KMT2A rearrangements, suggesting a subset of patients that may be more responsive to the effects of CD47 blockade. As this drug is being evaluated for use in other malignancies, future studies may focus on investigating the importance of biomarker-based patient selection. Full article

Despite advances in outcome, one third of children with acute myeloid leukemia (AML) relapse, and less than half will achieve long-term survival. Relapse in AML has been shown to be driven in part by leukemic stem cells (LSCs), highlighting the unmet medical need to better characterize and target this therapy-resistant cell population. Micro-array profiling of pediatric AML subpopulations (LSCs and leukemic myeloblasts) and their healthy counterparts revealed nidogen-1 (NID1) as expressed in both leukemic subpopulations while absent in the hematopoietic stem cell. Using the TARGET dataset including pediatric AML patients (n = 1025), NID1 expression showed a correlation with worse event-free survival and KMT2A rearrangements. Drug response profiling of a NID1 knockdown model demonstrated differential sensitivity to HSP90 inhibition. RNA sequencing and gene set enrichment analysis between NID1^high and NID1^low phenotypes showed involvement of NID1 in mitochondrial metabolic pathways known to be enriched in LSCs. Altogether, this study highlights NID1 as a novel oncogene associated with worse EFS and metabolic LSC phenotype in AML. NID1 could serve as a biomarker and aid in further mapping LSCs to establish therapeutic strategies tackling the high relapse rates in pediatric AML. Full article

Background: KMT2A rearrangements occur in ~10% of acute myeloid leukemia (AML) cases and are critical for classification, risk stratification, and use of targeted therapy. However, insertions involving the KMT2A gene can evade detection using chromosomal analysis and/or fluorescence in situ hybridization (FISH). Methods: We present a case of a 22-year-old woman with acute monoblastic leukemia harboring a cryptic KMT2A::AFDN fusion identified by RNA sequencing. Initial FISH showed a 3′ KMT2A deletion, while conventional karyotyping and the automated bioinformatic pipeline for optical genome mapping (OGM) did not identify the canonical translocation. Results: To resolve these discrepancies, metaphase KMT2A FISH (break-apart fusion probe) was performed to assess whether KMT2A was translocated to another chromosome. However, the results did not support this possibility. As the fusion signal remained on the normal chromosome 11, with the 5′ KMT2A signal localized to the derivative chromosome 11. A subsequent manual review of the OGM data revealed a cryptic ~300 kb insertion of AFDN into the 3′ region of KMT2A, reconciling the discrepancies between chromosomal analysis, FISH, and RNA fusion results. Conclusions: This case highlights the importance of integrating multiple testing modalities with expert review when there is a discrepancy. Our findings emphasize the need for a comprehensive approach to genomic assessment to enhance diagnostic accuracy and guide therapeutic decision-making. Full article

Background/Objectives: Infants with KMT2A-rearranged B-cell acute lymphoblastic leukemia (ALL) have high rates of relapse and poor survival compared with children. Few new therapies have been identified over the past twenty years. The aim of this study was to identify existing anti-cancer agents that have the potential to be repurposed for the treatment of infant ALL. Methods: Eight extensively characterized infant ALL cell lines were treated with 62 anti-neoplastic drugs in vitro to identify agents that exhibit significant cytotoxicity. From this screen, we selected the most effective and clinically translatable agent for further in vitro and in vivo assessment to determine the potential for use in the clinical setting. Results: Our anti-cancer drug screen revealed significant activity of dactinomycin across all infant ALL cell lines. Further in vitro testing identified low half-maximal inhibitory concentrations (IC₅₀) across our infant ALL cell lines in the nanomolar range. Combination testing with the conventional chemotherapeutic agents currently used to treat infants with ALL demonstrated additivity with cytarabine. In vivo assessment of dactinomycin identified 36 μg/kg as the maximum tolerated dose, with unacceptable toxicities at higher dose treatment. Treatment using doses of 18 μg/kg administered either once or twice a week derived a small but significant survival benefit in patient-derived xenografts. Conclusions: Dactinomycin is extensively used for the treatment of solid tumors in children and has an acceptable safety profile when used to treat infants in this context. However, despite being readily translational and exhibiting promising in vitro cytotoxicity, dactinomycin showed limited efficacy in vivo and therefore does not represent a priority candidate for integrating into therapy for infants with ALL. Full article