Relapsed Acute Lymphoblastic Leukemia Research Articles

PRC2 Inhibitors Overcome Glucocorticoid Resistance Driven by NSD2 Mutation in Pediatric Acute Lymphoblastic Leukemia.

Mutations in epigenetic regulators are common in relapsed pediatric acute lymphoblastic leukemia (ALL). Here, we uncovered the mechanism underlying the relapse of ALL driven by an activating mutation of the NSD2 histone methyltransferase (p.E1099K). Using high-throughput drug screening, we found that NSD2-mutant cells were specifically resistant to glucocorticoids. Correction of this mutation restored glucocorticoid sensitivity. The transcriptional response to glucocorticoids was blocked in NSD2-mutant cells due to depressed glucocorticoid receptor (GR) levels and the failure of glucocorticoids to autoactivate GR expression. Although H3K27me3 was globally decreased by NSD2 p.E1099K, H3K27me3 accumulated at the NR3C1 (GR) promoter. Pretreatment of NSD2 p.E1099K cell lines and patient-derived xenograft samples with PRC2 inhibitors reversed glucocorticoid resistance in vitro and in vivo. PRC2 inhibitors restored NR3C1 autoactivation by glucocorticoids, increasing GR levels and allowing GR binding and activation of proapoptotic genes. These findings suggest a new therapeutic approach to relapsed ALL associated with NSD2 mutation. SIGNIFICANCE: NSD2 histone methyltransferase mutations observed in relapsed pediatric ALL drove glucocorticoid resistance by repression of the GR and abrogation of GR gene autoactivation due to accumulation of K3K27me3 at its promoter. Pretreatment with PRC2 inhibitors reversed resistance, suggesting a new therapeutic approach to these patients with ALL.This article is highlighted in the In This Issue feature, p. 1.

Combination of invasive aspergillosis and mucormycosis in children: a case report and the results of a multicenter study

Objective. To study risk factors, etiology, clinical signs and treatment outcomes of invasive aspergillosis (IA) and mucormycosis combination (IAM) in children. Materials and Methods. A retrospective review of Saint-Petersburg register (1998–2021) of patients with IA was done and children with IAM were included. EORTC/MSGERG 2019 criteria were used for diagnosing and treatment results evaluation of invasive mycosis. We presented a clinical case of IAM in a child with acute lymphoblastic leukemia relapse. Results. A total of 12 children with IAM were included. They accounted 8% of all pediatric patients with invasive aspergillosis (n = 152). IAM was diagnosed in children with hematological malignancies and solid tumors from 4 to 16 years (median age – 11.5 years), mostly in girls (83%). Main risk factors of IAM were prolonged lymphopenia (75%, median 22 days) and neutropenia (67%, median 30 days) due to chemotherapy, systemic corticosteroids and/or immunosuppressive therapy, as well as HSCT. The predominant etiological agents of IA were Aspergillus niger (33%), A. nidulans (33%) and A. fumigatus (17%), of mucormycosis – Lichtheimia corymbifera (50%) and Rhizomucor spp. (50%). Based on EORTC/MSGERG 2019 criteria, «proven» mucormycosis was diagnosed in 83% of patients, «probable» – in 17%. «Probable» IA was found in 100% of patients. The most common clinical sites of IAM were the lungs (75%) and paranasal sinuses (43%), multifocal involvement was revealed in 33% of patients. Mucormycosis developed during antifungal therapy of IA in 83% of patients. Antifungal therapy of mucormycosis received 75% of patients (amphotericin B lipid complex – 89%, posaconazole – 78%, caspofungin – 33%), combined antifungal therapy – 33%, surgery – 50%; combination of surgical and antifungal treatment was used in 42% of patients. The overall 12-week survival was 77.8%. The use of combined surgical and antifungal treatment significantly improved the survival of children with IAM (p = 0.023). Conclusions. Mucormycosis was diagnosed in 8% of children with IA. IAM developed mostly in patients with hematological malignancies (83%), prolonged lymphopenia (75%) and neutropenia (67%) against the background of chemotherapy, systemic corticosteroids and/or immunosuppressive therapy, as well as HSCT. In 83% of patients mucormycosis was diagnosed during antifungal therapy for IA. The development of IAM increased overall 12-week mortality (50%). The combination of antifungal therapy with surgical treatment significantly improved prognosis of IAM (p = 0.023).

Protocol ALL-IC BFM 2002: Outcomes of Pediatric Acute Lymphoblastic Leukemia Treatment under Multi-Center Clinical Trial

Background. Programs of pediatric acute lymphoblastic leukemia (ALL) treatment, developed by the BFM (Berlin-Frankfurt -Munster) Group in 2002, remain one the most effective in the world. Long-term (10-15 years) overall survival in ALL children is above 90 %. Great progress in ALL treatment provided ground for including the ALL-IC BFM 2002 protocol into the Clinical Guidelines in 2020 (ID: 529). Aim. To present the outcomes of ALL treatment in children according to ALL-IC BFM 2002 under the multi-center clinical trial. Materials & Methods. From 01.11.2003 to 12.10.2021 the multi-center retrospective-prospective trial included 433 patients with newly diagnosed ALL, aged between 3 months and 21 years. The patients were aged from 0 to 12 (n = 344), from 12 to 18 (n = 70), and older than 18 years (n = 19). All of them were treated with ALL-IC BFM 2002. Overall (OS), disease-free (DFS), and event-free (EFS) survivals were estimated as of 01.12.2021. Results. In the vast majority of patients (97.9 %, n = 424) complete clinical hematological remission was reached by Day 33 of the ALL-IC BFM 2002 treatment. The 10-year OS was 91.8 ± 1.5 %, DFS was 87.4 ± 1.8 %, and EFS was 84.1 ± 1.9 %. The 10-year OS in the groups of standard- and intermediate-risk patients was 92.8 ± 1.7 % and 94.6 ± 2.6 %, respectively, whereas in high-risk ALL relapse patients it was 71.1 ± 11.1 %. Conclusion. The ALL-IC BFM 2002 protocol for treating pediatric ALL is reproducible in federal and regional clinics. The outcomes of the ALL-IC BFM 2002 treatment appeared to be impressive. They are comparable to those achieved in leading European and American clinics. To improve survival of high-risk patients, additional stratifying criteria are required, one of which should be the assessment of minimal residual disease (MRD). MRD detection became a basis for prognostic risk stratification under ALL-IC BFM 2009, the results of which will be presented in 2022-2023.

Newly Developed Treatments for Acute Lymphoblastic and Acute Myeloid Leukemia

Chemotherapy has been dominating the field of cancer treatment for a long time, however, its limitations have been revealed over time. Therefore, several antigen proteins and chimeric antigen receptorT cells (CAR-T) involved in the immunotherapy of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) have been introduced. This paper provides details on the mechanisms, implemented investigations, and drawbacks of the immunotherapy for ALL and AML. Current studies have shown that CAR-T cell therapy can eliminate pediatric ALL relapse along with treating B cell ALL. With the appearance of CAR-T cell therapy, especially CD19-, CD20-, and CD22-directed CAR-T cells, aggressive acute lymphomas involving ALL become treatable. Studies have also shown that AML can be treated with FLT3 inhibitors and immunotherapy including monoclonal antibodies (mbA) and CD33-, CD123-directed CAR-T cells. Anti-CD33 monoclonal antibodies can combine with calicheamicin, a cytotoxic agent in DNA strand cleavage, and monotherapy of gemtuzumab ozogamicin (GO), an antibody-drug conjugate, and this combination has been proved to extend the overall survival of both newly treated patients and R/R AML patients who are unable to tolerate standard chemotherapy.

Genetic Profiling in Children With Acute Lymphoblastic Leukemia Referred for Allogeneic Hematopoietic Stem Cell Transplantation.

IntroductionHematopoietic stem cell transplantation (HSCT) is the essential and often the only curative therapeutic option in high risk and relapsed pediatric acute lymphoblastic leukemia (ALL).MethodsThe objective of the study was to investigate whole-genome expression in children with high risk or relapsed ALL referred for HSCT. Gene expression was assessed in 18 children with ALL referred for HSCT (10 high risk, 8 relapsed; median age of 9.4 years) and in a control group of 38 obese children (median age of 14.1 years). Whole-genome expression was assessed in leukocytes using GeneChip® HumanGene 1.0 ST microarray.ResultsThe analysis of genomic profiles revealed a significantly lower expression of 21 genes with a defined function, involved in immunoglobulin production, lymphocyte function, or regulation of DNA processing in ALL patients referred for HSCT compared with the control group.ConclusionGenome expression of patients with ALL in remission referred to HSCT revealed deep immunosuppression of both B-cell and T-cell lineages, which may increase the probability of donor cell engraftment.

In This Issue

See article, p. 16.B-precursor acute lymphoblastic leukemia (B-ALL) relapse often involves the central nervous system (CNS). In this article, Vanner, Dobson, et al. characterize B-ALL subclones with differential CNS involvement in patient-derived xenografts. By comparing transcriptional profiles, the authors identify complement component C3 and stem cell, metabolic, and mRNA translation pathways enriched in subclones with preferential CNS residence regardless of mutational composition. These findings are validated by proteomics and by genetic or pharmacologic targeting of the candidate pathways. The protein translation inhibitor omacetaxine mepesuccinate strongly reduces CNS infiltration.See article, p. 32.In this study, Petti et al. evaluated mechanisms that contribute to the relapse of patients with acute myeloid leukemia (AML) after therapy. Bone marrow samples from presentation and relapse from six patients with normal karyotype AML were subjected to enhanced whole-genome sequencing to identify all somatic mutations and their evolution. Single-cell RNA sequencing defined transcriptional and cellular changes at relapse. Each case had a unique set of genetic and transcriptional adaptations associated with relapse, but most acquired a conserved relapse-enriched leukemia cell (RELC) signature that had features of stemness, quiescence, and adhesion.See article, p. 50.Diffuse large B-cell lymphomas (DLBCL) are dependent on anaplerotic glutaminolysis driven by SIRT3. Li et al. show that the metabolic collapse induced by SIRT3 depletion leads to marked repression of ATF4 target genes that are highly expressed in DLBCL. ATF4 is required for DLBCL cell proliferation and is translationally activated when sensing depletion of nonessential amino acids (NEAA). Reciprocally, loss of SIRT3 induces accumulation of NEAAs due to induction of autophagy, which in turn suppresses ATF4 translation, further aggravates nutrient starvation, and ultimately leads to cell death, which is further enhanced by exposure to GCN2 inhibitors.See article, p. 66.Although 80% to 90% of patients treated with CD19 CAR T-cell therapy for ALL achieve remission, half will relapse. Biomarkers predicting relapse have so far been unknown. In this study, Pulsipher et al. hypothesize that the presence of minimal residual disease detected by next-generation sequencing (NGS-MRD) after tisagenlecleucel therapy would predict relapse of both CD19+ and CD19− blasts. They demonstrate that any level of NGS-MRD positivity was highly associated with relapse risk. A combination of early loss of B-cell aplasia with NGS-MRD >0 predicted relapse with sufficient time to intervene with various approaches aimed at preventing relapse.

Novel Insights into Pediatric Acute Lymphoblastic Leukemia Ophthalmic Relapses from a Nationwide Cohort Study.

Ten to fifteen percent of children with acute lymphoblastic leukemia (ALL) relapse following treatment. Of these, less than 2% display ophthalmic relapses, which owing to their scarcity, are largely undocumented, leaving clinicians with few diagnostic and therapeutic recommendations, despite serious functional sequelae. We conducted a French multicenter retrospective study to collect all clinical, radiological, biological, and therapeutic data, and outcomes for children with ALL ophthalmic relapses. From 2000 to 2020, 20 ophthalmic relapses occurring after first-line therapy performed before January 1st, 2017 were included in our study: 14 B-ALL and 6 T-ALL. Fifteen patients (75%) had concomitant involvement of the central nervous system, and 11 (55%) a combined bone marrow relapse. Only 1 had an isolated ophthalmic relapse. Eight children (40%) died, 7 from a refractory disease and 1 from toxic death, and 4 patients relapsed. With a median follow-up of 63.1 months, 8 patients are currently alive in continuous complete remission with only 2 displaying severe ophthalmic sequelae. Although rare, ophthalmic relapse could have a significant impact on the functional prognosis of survivors. Their management must be multidisciplinary, with a central role given to ophthalmologists.

Acute tetraparesis revealing acute lymphoblastic leukemia relapse: A case report and literature review

Acute lymphoblastic leukemia (ALL) is the most common cancer of childhood. While some 5 to 8% of ALL cases will have neurological involvement at initial presentation, up to 30% of relapses have neurological manifestations. We present the case of a pediatric ALL with meningo-radiculoneuropathy revealing a relapse while on maintenance therapy. Our patient presented the Philadelphia mutation, that is the t(9;22), and thus was at high risk of neurological involvement. The diagnosis of relapse was based on neuroimaging and CSF study. Treatment entailed modified Hyper CVAD chemotherapy with repeated intrathecal treatment until CSF clearance. Outcome was favorable with gradual regression of neurological symptoms.

PON2 blockade overcomes dexamethasone resistance in acute lymphoblastic leukemia

ABSTRACT Objectives The high frequency of chemotherapy resistance is ultimately responsible for clinical relapse in acute lymphoblastic leukemia (ALL). Nevertheless, the molecular mechanism relevant to glucocorticoid (GC) resistance remains ambiguous. Methods Quantitative real-time polymerase chain reaction and Western blot were performed to detect the expressions of paraoxonase 2 (PON2), Bcl-2 and Bax. shRNA was used to knockdown PON2 expression in SUP-B15 and REH cell. CCK-8 and flow cytometry assay were conducted to monitor the changes of proliferation and apoptosis in ALL cells. The growth of ALL REH cells in vivo was determined using transplanted tumor model. Results This study was designed to identify GC resistance-associated genes by means of the transcriptome chip from the public Gene Expression Omnibus database, and preliminarily investigation of dexamethasone (DEX)-resistance mechanism in ALL. We disclosed that PON2 expression was elevated in ALL patients and especially higher in DEX-resistance ALL patients. Then, cell apoptosis assay suggested that silencing of PON2 dramatically promoted in DEX-resistant ALL cells apoptosis and the activity of Caspase 3 induced by DEX administration. In xenograft tumor model, PON2 knockdown significantly reduced DEX-resistant ALL cells growth in immunodeficient mice. Conclusions Collectively, inhibition of PON2 may represent a novel method to restore the sensitivity of treatment-resistant ALL to GC-induced cell death.

Fungal diagnostic testing and therapy: navigating the neutropenic period in children with high-risk leukemia

AbstractChildren, adolescents, and young adults receiving intensive chemotherapy for acute myeloid leukemia or high-risk or relapsed acute lymphoblastic leukemia sustain prolonged periods of neutropenia that predispose them to invasive fungal disease (IFD). For many decades the standard of care for these patients was to initiate empirical antifungal therapy after a period of prolonged fever and neutropenia. Recent publications have yielded important evidence on the utility of different diagnostic and therapeutic approaches aimed at reducing the impact of IFD among these patients during these vulnerable periods. This case-based review highlights and interprets the published data to provide context for the IFD diagnostic and therapeutic recommendations proposed in multiple published guidelines. Personalized approaches are offered at points where evidence is lacking. Time points where specific knowledge gaps exist are identified along the clinical trajectory of the prolonged neutropenic period to illustrate areas for future investigation.

Therapeutic approach and outcome of children with Philadelphia chromosome-positive acute lymphoblastic leukemia at first relapse in the era of tyrosine kinase inhibitors: An SFCE retrospective study.

Since the introduction of tyrosine kinase inhibitors (TKIs), the profile of pediatric relapse of Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) has changed. However, the management of pediatric Ph+ ALL relapses is not currently standardized. We retrospectively analyzed the therapeutic strategies and outcomes of pediatric Ph+ ALL patients in first relapse who were initially treated with a TKI-containing regimen in one of the French pediatric hematology centers from 2004 to 2019. Twenty-seven children experienced a Ph+ ALL relapse: 24 (89%) had an overt relapse and three a molecular relapse. Eight involved the central nervous system. A second complete remission (CR2) was obtained for 26 patients (96%). Induction consisted of nonintensive chemotherapy for 13 patients (48%) and intensive chemotherapy for 14 (52%). Thirteen patients (48%) received consolidation. Allogenic hematopoietic stem cell transplantation (alloHSCT) was performed for 21 patients (78%). The TKI was changed for 23 patients (88%), mainly with dasatinib (n=15). T315I was the most common mutation at relapse (4/7). The 4-year event-free survival and survival rates were 60.9% and 76.1%, respectively. Survival was positively associated with alloHSCT in CR2. We show that pediatric first-relapse Ph+ ALL reinduces well with a second course of TKI exposure, despite the use of different therapeutic approaches. The main prognostic factor for survival was alloHSCT in CR2. Because of the small size of the cohort, we could not draw any conclusions about the respective impact of TKIs, but the predominance of the T315I mutation should encourage careful consideration of the TKI choice.

Genetic and Epigenetic Targeting Therapy for Pediatric Acute Lymphoblastic Leukemia.

Acute lymphoblastic leukemia is the most common malignancy in children and is characterized by numerous genetic and epigenetic abnormalities. Epigenetic mechanisms, including DNA methylations and histone modifications, result in the heritable silencing of genes without a change in their coding sequence. Emerging studies are increasing our understanding of the epigenetic role of leukemogenesis and have demonstrated the potential of DNA methylations and histone modifications as a biomarker for lineage and subtypes classification, predicting relapse, and disease progression in acute lymphoblastic leukemia. Epigenetic abnormalities are relatively reversible when treated with some small molecule-based agents compared to genetic alterations. In this review, we conclude the genetic and epigenetic characteristics in ALL and discuss the future role of DNA methylation and histone modifications in predicting relapse, finally focus on the individual and precision therapy targeting epigenetic alterations.

Alteration of the immune environment in bone marrow from children with recurrent B cell precursor acute lymphoblastic leukemia.

Due to the considerable success of cancer immunotherapy for leukemia, the tumor immune environment has become a focus of intense research; however, there are few reports on the dynamics of the tumor immune environment in leukemia. Here, we analyzed the tumor immune environment in pediatric B cell precursor acute lymphoblastic leukemia by analyzing serial bone marrow samples from nine patients with primary and recurrent disease by mass cytometry using 39 immunophenotype markers, and transcriptome analysis. High‐dimensional single‐cell mass cytometry analysis elucidated a dynamic shift of T cells from naïve to effector subsets, and clarified that, during relapse, the tumor immune environment comprised a T helper 1‐polarized immune profile, together with an increased number of effector regulatory T cells. These results were confirmed in a validation cohort using conventional flow cytometry. Furthermore, RNA transcriptome analysis identified the upregulation of immune‐related pathways in B cell precursor acute lymphoblastic leukemia cells during relapse, suggesting interaction with the surrounding environment. In conclusion, a tumor immune environment characterized by a T helper 1‐polarized immune profile, with an increased number of effector regulatory T cells, could contribute to the pathophysiology of recurrent B cell precursor acute lymphoblastic leukemia. This information could contribute to the development of effective immunotherapeutic approaches against B cell precursor acute lymphoblastic leukemia relapse.

Effects of second transplantation with T-cell-replete haploidentical graft using low-dose anti-thymocyte globulin on long-term overall survival in pediatric patients with relapse of leukemia after first allogeneic transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the preferred treatment for children with high-risk hematologic malignancies, but post-allo-HSCT relapse has a poor prognosis and limited treatment options. We evaluated the feasibility, outcome, and risk factors influencing survival after T-cell-replete haploidentical HSCT with low-dose anti-thymocyte globulin (ATG) in 30 patients with post-allo-HSCT relapse of acute lymphoblastic leukemia and acute myeloid leukemia. Overall, 50% of the patients had complete remission (CR) before the second transplant and the overall survival (OS) rate was 52%. In surviving patients (median follow-up 614days), Kaplan-Meier analysis revealed estimated 2-year leukemia-free survival and OS rates of 48.1% and 61.1%, respectively. Cumulative incidences of 2-year non-relapse mortality and relapse were 24.7% and 36.3%, respectively. Achieving CR before the second allo-HSCT was a predominant independent prognostic factor identified in the multivariate analysis, with a significantly improved 2-year OS rate of 86.7%. T-cell-replete haplo-HSCT with low-dose ATG for second allo-HSCT may benefit a selected patient population.

Cardiac Relapse of Acute Lymphoblastic Leukemia Following Hematopoietic Stem Cell Transplantation: A Case Report and Review of Literature.

Simple SummaryWe present a case of a pediatric patient with symptomatic leukemia involving the heart without bone marrow involvement. The case is followed by a literature review of advances in leukemia treatment including immunotherapy, CAR T-cell therapy, improvement in the treatment of graft-versus-host disease, and the applicability of these treatments to leukemia involving areas outside of the bone marrow. We also explore the feasibility of treatments such as CAR T-cell therapy and blinatumomab and the associated risks for treating patients with leukemia infiltrating the heart.Isolated extramedullary relapse of acute lymphoblastic leukemia (ALL) occurs in soft tissues and various organs outside the testis and central nervous system. Treatments such as hematopoietic stem cell transplantation and more novel modalities such as immunotherapy have eradicated ALL at extramedullary sites. In some instances, survival times for relapsed ALL at these sites are longer than those for relapsed disease involving only the bone marrow. Isolated relapse of ALL in the myocardium is rare, especially in children, making diagnosis and treatment of it difficult. More recent treatment options such as chimeric antigen receptor T-cell therapy carry a high risk of cytokine release syndrome and associated risk of worsening cardiac function. Herein we present the case of an 11-year-old boy who presented with relapsed symptomatic B-cell ALL in the myocardium following allogeneic hematopoietic stem cell transplantation. This is an unusual presentation of relapsed ALL and this case demonstrates the associated challenges in its diagnosis and treatment. The case report is followed by a literature review of the advances in treatment of pediatric leukemia and their application to extramedullary relapse of this disease in particular.

Other (Non-CNS/Testicular) Extramedullary Localizations of Childhood Relapsed Acute Lymphoblastic Leukemia and Lymphoblastic Lymphoma-A Report from the ALL-REZ Study Group.

Children with other extramedullary relapse of acute lymphoblastic leukemia are currently poorly characterized. We aim to assess the prevalence and the clinical, therapeutic and prognostic features of extramedullary localizations other than central nervous system or testis in children with relapse of acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma (LBL) treated on a relapsed ALL protocol. Patients and Methods: Patients with relapse of ALL and LBL, treated according to the multicentric ALL-REZ BFM trials between 1983 and 2015, were analyzed for other extramedullary relapse (OEMR) of the disease regarding clinical features, treatment and outcome. Local treatment/irradiation has been recommended on an individual basis and performed only in a minority of patients. Results: A total of 132 out of 2323 (5.6%) patients with ALL relapse presented with an OEMR (combined bone marrow relapse n = 78; isolated extramedullary relapse n = 54). Compared to the non-OEMR group, patients with OEMR had a higher rate of T-immunophenotype (p < 0.001), a higher rate of LBL (p < 0.001) and a significantly different distribution of time to relapse, i.e., more very early and late relapses compared to the non-OEMR group (p = 0.01). Ten-year probabilities of event-free survival (pEFS) and overall survival (pOS) in non-OEMR vs. OEMR were 0.38 ± 0.01 and 0.32 ± 0.04 (p = 0.0204) vs. 0.45 ± 0.01 and 0.37 ± 0.04 (p = 0.0112), respectively. OEMRs have been classified into five subgroups according to the main affected compartment: lymphatic organs (n = 32, 10y-pEFS 0.50 ± 0.09), mediastinum (n = 35, 10y-pEFS 0.11 ± 0.05), bone (n = 12, 0.17 ± 0.11), skin and glands (n = 21, 0.32 ± 0.11) and other localizations (n = 32, 0.41 ± 0.09). Patients with OEMR and T-lineage ALL/LBL showed a significantly worse 10y-pEFS (0.15 ± 0.04) than those with B-Precursor-ALL (0.49 ± 0.06, p < 0.001). Stratified into standard risk (SR) and high risk (HR) groups, pEFS and pOS of OEMR subgroups were in the expected range whereas the mediastinal subgroup had a significantly worse outcome. Subsequent relapses involved more frequently the bone marrow (58.4%) than isolated extramedullary compartments (41.7%). In multivariate Cox regression, OEMR confers an independent prognostic factor for inferior pEFS and pOS. Conclusion: OEMR is adversely related to prognosis. However, the established risk classification can be applied for all subgroups except mediastinal relapses requiring treatment intensification. Generally, isolated OEMR of T-cell-origin needs an intensified treatment including allogeneic stem cell transplantation (HSCT) as a curative approach independent from time to relapse. Local therapy such as surgery and irradiation may be of benefit in selected cases. The indication needs to be clarified in further investigations.

Dysregulation of Epigenetic Landscape Uncovered the Mechanisms Underlying the Relapse of Pediatric Acute Lymphoblastic Leukemia with NSD2 Mutation

Background: Relapse from acute lymphoblastic leukemia (ALL) is one of the most common causes of pediatric cancer-related death. Early relapse of ALL is associated with recurrent mutations of histone methyltransferase NSD2 (nuclear receptor binding SET domain protein 2), which is specific for H3K36me2, suggesting a link to therapy resistance or other mechanisms underlying relapse such as central neural system (CNS) infiltration. NSD2 p.E1099K affects gene expression through disturbing the balance of H3K36me2/H3K27me3. Using CRISPR/Cas9-edited isogenic ALL cell lines and PDX cells, we found that NSD2 p.E1099K drives oncogenic programming, CNS infiltration and glucocorticoid (GC) resistance. However, the molecular mechanisms underlying the relapse of this subtype of ALL are still under investigation.Aim: To elucidate the epigenetic landscape underlying the mechanism of the relapse of pediatric ALL with NSD2 mutation.Methods: We performed in vivo experiments to observe tumor burden, leukemia cell infiltration and survival of the NOD/SCID mice injected with a NSD2 p.E1099K mutation knock-out SEM cell line and knock-in CEM cell line. We determined transcriptome (RNA-Seq), chromatin accessibility (ATAC-Seq) in isogenic RCH-ACV, SEM, RPMI-8402 and CEM cell lines, transcription factor binding and histone modification (ChIP-Seq) and 3D organization (Hi-C) in RCH-ACV cells. Finally, we integrated analysis of RNA-Seq, ATAC-Seq, ChIP-Seq and Hi-C to comprehensively disclose the epigenetic landscape in ALL with NSD2 mutation.Results: NOD/SCID mice xenografted with NSD2 mutant cells developed high tumor burden and infiltration to spleen, liver and brain while the mice injected with WT cells accumulated significant less tumor cells and had extended survival. RNA-Seq analysis showed that reversion of NSD2 mutation to WT caused more genes downregulated while insertion of NSD2 mutation to WT cells led to more genes upregulated (Mutant vs WT: RCH-ACV 838 vs 494, SEM 1567 vs 1158, RPMI-8402 1922 vs 1745, CEM 1809 vs 1031). 50 upregulated genes and 3 downregulated genes were in common in B-ALL and T-ALL with NSD2 mutation. Most of the upregulated genes correlated with neural development and adhesion which might contribute to CNS infiltration (e.g., NCAM1 and NEO1). A few genes were associated with GC resistance such as decreased NR3C1 and increased NR3C2. Accordingly, ATAC-Seq showed that NSD2 mutant cells had more open chromatin peaks than those of WT (RCH-ACV 4853 vs 3212, SEM 10052 vs 7595, RPMI-8402 20392 vs 12133, CEM 10155 vs 6437). ChIP-Seq revealed general large gains of H3K36me2 in intergenic regions in NSD2 mutant cells. Importantly, genes upregulated with NSD2 mutation (e.g., NCAM1 and NEO1) lost H3K27me3 at promoters but gained H3K36me2 at promoters and whole gene bodies, accompanied with increased H3K27ac at enhancers. Conversely, a small subset of genes gained H3K27me3 and lost H3K36me2 in their promoters. Concentrated H3K36me2 in gene bodies diffused and broadened was less prominent and H3K27me3 accumulation became dominant. This for example was associated with repression of NR3C1 to drive GC resistance of NSD2 mutant cells. Genes upregulated in NSD2 mutant cells were enriched for binding sites for lymphoid transcriptional activators such as EBF1 and IRF2. The promoters of the downregulated genes had motifs for transcription factors poorly expressed in lymphoid cells and were enriched for binding sites for the BCL6 transcriptional repressor. Hi-C analysis revealed 430 topologically associated domains (TADs) with increased loop interactions while 136 TADs with decreased interactions were in NSD2 mutant cells compared to WT cells. Overall, 491 regions switched from compartment A to B and 444 regions switched from B to A in NSD2 mutant cells compared to WT cells. Compartment switching from inactive B to active A correlated with upregulated gene expression levels while the reverse was true for switching from A to B. Increased intra-TAD interactions were linked to upregulated genes while decreased intra-TAD interactions were linked to downregulated genes.Conclusions: The NSD2 mutation led to increased tumor burden, CNS infiltration and glucocorticoid resistance due to dysregulation of epigenetic patterns and 3D chromatin architecture, indicating mechanisms underlying the relapse of pediatric ALL and potential therapeutic targets in ALL with NSD2 mutation. DisclosuresLicht: Epizyme: Research Funding.

Tisagenlecleucel Therapy Is Safe and Effective for Children with Down Syndrome with ALL in First Relapse

Introduction: Children with Down Syndrome (DS) have a 20-fold increased incidence of acute lymphoblastic leukemia (ALL) and a 70% higher risk of relapse than children with ALL and no DS. Treatment for DS children with relapsed ALL is challenging due to the high treatment-related mortality associated with both intensive chemotherapy and hematopoietic stem cell transplantation (HSCT) as well as high rates of second relapse. Outcomes for relapsed ALL in DS are dismal, with recent studies citing an event-free survival (EFS) as low as 17%. Alternative treatment approaches are needed for this patient population. Treatment with anti-CD19 chimeric antigen receptor T-cells (CARTs) have shown high remission rates in patients with multiple relapsed/refractory ALL with an acceptable safety profile. CARTs are generally not indicated for first relapse of ALL; DS-specific indications for CARTs do not exist. In Ontario, due to the specific susceptibility of children with DS-ALL, CARTs were made available to this population upon first relapse. We describe the population-based Canadian experience using CARTs for first relapse of DS-ALL.Methods: Efficacy and safety data on all children referred for CARTs at the Hospital for Sick Children, in Toronto, Canada were retrospectively collected in a central database and validated by treating clinicians. Here we report all patients with DS suffering a first relapse of ALL at age <18 years referred for commercially available CARTs (tisagenlecleucel) between 2019 and 2021.Results: Five patients with DS received tisagenlecleucel for first relapse of ALL during the study period. Median age at original diagnosis was 6.3 years (range 3.4-11.5). Four patients presenting with National Cancer Institute (NCI) standard risk and one with NCI high-risk disease were initially treated on Children's Oncology Group based protocols. Four patients presented with relapse >36 months from diagnosis and one patient with early relapse. Mononuclear cells were successfully collected for all patients on the first attempt. Patients were bridged from collection to infusion with low intensity chemotherapy regimens. Tisagenlecleucel was successfully manufactured for all patients and infused at a median of 69 days (range 56-101) from collection of T cells. Four patients developed CRS: two patients grade 1, one patient grade 2, and one patient grade 4 requiring ICU care and treatment with tocilizumab and steroid. All patients achieved minimal residual disease (MRD) negative remission one month after infusion, with B-cell aplasia. Two patients showed early (< 6months post infusion) B-cell recovery consistent with CAR T-cell loss; both received off-label reinfusions of tisagenlecleucel and again achieved B-cell aplasia. One patient had a seizure with the first Fludarabine dose of lymphodepleting (LD) chemotherapy for re-infusion and was found to have elevated intracranial pressure. After treatment with Topiramate and anti-seizure prophylaxis the patient tolerated LD chemotherapy without further neurological events. No patient received further ALL therapy; none went on to HSCT. One patient suffered a CD19-negative relapse 7 months post infusion and was transitioned to palliative-intent treatment. Two patients developed prolonged neutropenia with one patient showing recovery (ANC>1x10E9/l) at 5 months post infusion and the patient who had relapsed disease remained neutropenic until relapse. Infectious complications in the first 6 months post infusion were rare. One patient, who was not neutropenic, required two hospital admissions for line related sepsis. With a median follow-up time of 519 days (range 197-785), the 1-year estimated EFS and overall survival were both 80% (95 th confidence interval 52-100%; Figure 1).Conclusions: Tisagenlecleucel was safe and effective in a small cohort of children with DS and first relapse of CD19+ ALL, with achievement of long-term remissions without further therapy, and an EFS superior to that seen in historical cohorts. Rate of acute complications were not increased compared with reported outcomes in patients without DS. Further evaluation of tisagenlecleucel in this setting is warranted. [Display omitted] DisclosuresKrueger: KITE/Gilead: Consultancy; Novartis: Consultancy; SOBI: Consultancy. Whitlock: Sobi Pharmaceuticals: Consultancy; Novartis: Research Funding; Amgen; Jazz Pharmaceuticals: Honoraria. Gupta: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure:tisagenlecleucel for early B-cell recovery

Frequency and Outcome of Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia with BCR-ABL1 Clonal Hematopoiesis after Blast Clearance: Results from the Graaph-2014 Trial

BackgroundIG/TR-based minimal residual disease (MRD) is a faithful marker of response to therapy and the strongest predictor of relapse in acute lymphoblastic leukemia (ALL). In adults with Philadelphia chromosome-positive (Ph+) ALL, MRD is commonly monitored by BCR-ABL1 transcript quantification, although its prognostic significance has not been compared to IG/TR MRD to date. Recently, it has been shown that BCR-ABL1 rearrangement may be found and persist in non-lymphoblastic cells in some patients. In the prospective GRAAPH-2014 trial, using a dual IG/TR and BCR-ABL1 MRD monitoring, we aimed to study the biological and clinical significance of persistent BCR-ABL1 clonal hematopoiesis (CH) in adults with de novo Ph+ ALL.Patients and MethodsThe study comprised 156 adults with de novo Ph+ ALL randomized in the GRAAPH-2014 trial. Bone marrow (BM) and peripheral blood (PB) follow-up (FU) samples were collected after each treatment cycle and before hematopoietic stem cell transplantation (HSCT). MRD monitoring was performed by quantification of both BCR-ABL1 transcripts and IG/TCR clonal rearrangements on all available samples and MRD quantification of genomic BCR-ABL1 breakpoint fusion was also performed for 37 patients. MRD results were considered discordant if more than one log10 difference or positivity/negativity discordance on the same FU sample was evidenced. Cell fractions from 14 peripheral blood mononuclear cells (PBMC) samples (T-cells, B-cells and monocytes) were FACS-sorted and evaluated for BCR-ABL1 expression. Achievement of major molecular response (MMR) defined as <0.1% BCR-ABL1/ABL1 ratio after the 4 treatment cycles (MRD4) was the primary endpoint of the clinical trial.ResultsQuantification of BCR-ABL1 transcripts and IG/TR MRD levels on 876 samples from 156 patients (456 BM and 542 PB) identified 54 out of 142 (38%) evaluable patients with consistently discordant MRD results in at least 3 different timepoints, suggesting the persistence of non-lymphoblastic BCR-ABL1-positive cells in these patients and BCR-ABL1 CH. Possible bias related to variable BCR-ABL1 expression was ruled out by genomic BCR-ABL1 quantification on 263 FU samples (r s=0.89, p<0.0001). Analysis of sorted PBMC fractions from discordant FU samples revealed the expression of BCR-ABL1 in mature B-cells, T-cells and/or monocytes in 11 patients, demonstrating the presence of BCR-ABL1 CH. Baseline characteristics of patients with BCR-ABL1 CH (CH+) showed no difference in terms of age, gender and white blood cell counts, but an enrichment in M-bcr breakpoints as compared to CH- patients (46.3% vs 17.1%, p<0.0001). As expected, the rate of MMR at MRD4 was lower (68% vs 95%, p<0.0001), with a trend for more patients who received alloSCT (38/54 (70%) vs 48/88 (55%), p=0.08).We then evaluated the clinical significance of BCR-ABL1 CH. Unexpectedly, CH+ patients had a significant lower cumulative incidence of relapse (CIR) (panel A, hazard ratio (HR) 0.37, 95% CI [0.15-0.90], p=0.03). However, this lower CIR did not translate into longer disease-free survival (DFS) (panel B, HR=0.85, 95% CI [0.44-1.63], p=0.63). Since an imbalance in alloSCT was observed between CH+ and CH- patients, we tested if the observed difference in CIR may be related to different alloSCT outcomes. When censoring patients at alloSCT, the difference in CIR was indeed no longer significant (subhazard ratio (SHR) 0.48, 95% CI [0.16-1.43], p=0.19). More interestingly, the benefit of alloSCT was restricted to CH- patients. Using alloSCT as a time-dependent variable, DFS was indeed improved by alloSCT in CH- (SHR 0.40, 95% CI [0.17-0.91], p=0.03, panel C) but not in CH+ patients (SHR 1.12, 95%CI [0.32-3.87], p=0.86, panel D) despite a non-significant interaction between CH status and alloSCT.ConclusionMore than one third of adults with de novo Ph+ ALL displays persistent measurable BCR-ABL1 signal during therapy, likely related to BCR-ABL1 CH. Strikingly, this condition is not associated with a higher risk of relapse nor with poorer overall outcomes in the GRAAPH-2014 trial. Moreover, our results suggest that patients with BCR-ABL1 CH may not be good candidates for alloSCT. By contrast, IG/TR MRD may allow to identify patients with the higher risk of relapse. These results highlight the need for implementation of IG/TR MRD in adult Ph+ ALL to guide therapeutic decisions. [Display omitted] DisclosuresRousselot: Incyte, Pfizer: Consultancy, Research Funding. Chalandon: Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Amgen: Other: Advisory Board; Incyte: Speakers Bureau; Incyte, BMS, Pfizer, Abbie, MSD, Roche, Novartis, Gilead, Amgen, Jazz, Astra Zenec: Other: Travel EXpenses, Accomodation. Straetmans: Alexion: Membership on an entity's Board of Directors or advisory committees. Huguet: Novartis: Other: Advisor; Jazz Pharmaceuticals: Other: Advisor; Celgene: Other: Advisor; BMS: Other: Advisor; Amgen: Other: Advisor; Pfizer: Other: Advisor. Dombret: Amgen: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria, Research Funding; Novartis: Research Funding; Pfizer: Honoraria, Research Funding; Servier: Research Funding; Abbvie: Honoraria; BMS-Celgene: Honoraria; Daiichi Sankyo: Honoraria. Boissel: SANOFI: Honoraria; CELGENE: Honoraria; Servier: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; PFIZER: Consultancy, Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Incyte: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; JAZZ Pharma: Honoraria, Research Funding.

Blinatumomab Is Cost-Effective Compared to Standard Chemotherapy for Children with High Risk Relapses of Acute Lymphoblastic Leukemia: A Cost-Effectiveness Analysis Using Population-Based Healthcare Data

▪Introduction: Though cure rates for childhood acute lymphoblastic leukemia (ALL) have improved significantly, outcomes for children with relapsed ALL remain poor. Novel immunotherapies have proved effective in relapsed disease. Blinatumomab, a bispecific T-cell engager targeting CD19, was recently shown to improve disease-free and overall survival among children with high-risk relapsed disease (Brown et al, 2021) prior to proceeding to stem cell transplant. Blinatumomab however also represents a significant cost burden to institutions and healthcare systems. Our objective was thus to determine the cost-effectiveness of blinatumomab vs. standard of care therapy among children with high-risk relapsed ALL.Methods: We used a childhood ALL-specific policy simulation model previously developed using real world clinical, healthcare utilization, and cost population-based data from Ontario, Canada, and restricted it to children with B-lineage ALL who relapsed with 18 months of their original diagnosis to capture a population of patients with high-risk relapse who survived their original month of re-induction chemotherapy. This model was combined with published data from the Children's Oncology Group randomized control study AALL1331 to estimate the long-term survival, healthcare costs and quality adjusted life years associated with two courses of blinatumomab vs. two courses of standard intensive chemotherapy, followed by stem cell transplant. Combining these two sources allowed for the creation of a multi-state survival model and the estimation of the impact of blinatumomab upon relapse and survival. Healthcare costs for the administration of blinatumomab or chemotherapy were sourced from administrative data, provincial formularies, and published sources. Lifetime costs and quality-adjusted life years were calculated while Monte Carlo simulation was used to propagate parameter uncertainty in the cost-effectiveness outcomes. All costs were calculated in Canadian dollars (CAD).Results: Blinatumomab was associated with on average higher life expectancy (43.4 years vs. 36.8 years) and a higher number of quality adjust life years [2.75 QALYs gained, 95 th confidence interval (95CI) -0.44 to 5.99] but higher costs (60,420 CAD, 95CI 26,794 - 94,047) compared to standard intensive chemotherapy. The incremental cost effectiveness ratio (ICER) associated with blinatumomab was 21,970 CAD/QALY gained. However, substantial uncertainty around model parameters resulted in wide confidence intervals around cost-effectiveness outcomes.Discussion: Initial evidence indicates that the use of blinatumomab in high-risk relapse of childhood ALL as compared to standard chemotherapy is associated with a cost-effectiveness ratio that is comparable to or lower than that associated with other interventions recently introduced in pediatric ALL, and represents a cost-effective intervention for this population. However, estimates are based on limited evidence; further research is necessary to better inform several model parameters and thereby decrease uncertainty in cost-effectiveness outcomes. DisclosuresGupta: Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees.