Mixed Phenotype Acute Leukemia Research Articles

Deciphering the Impact of Donor Telomere Length on Allogeneic Transplantation Outcomes: Telomere Length Matters More Than Age

Background Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for acute leukemia. The success of transplantation relies significantly on optimal donor selection, with the donor's age being a critical factor affecting recipient survival post allo-HSCT. Telomeres play a vital role in safeguarding genetic information and are considered biomarkers for biological aging. In patients with severe aplastic anemia undergoing allo-HSCT, shorter telomere length is strongly associated with adverse outcomes. However, the relationship between telomere length and transplant outcomes in patients with acute leukemia remains unexplored. Thus, this study aims to investigate the impact of donor telomere length on clinical outcomes following allo-HSCT. Methods This post hoc analysis included 863 patients with acute leukemia who underwent allo-HSCT at the First Affiliated Hospital of Zhejiang University between June 6, 2016, and March 4, 2022. The inclusion criteria were as follows: (1) patient age ≥ 10 years; (2) diagnosis of acute leukemia, including acute myeloid leukemia, acute lymphoblastic leukemia, and mixed phenotype acute leukemia; (3) availability of a pre-transplant blood sample from the donor before mobilization. Peripheral mononuclear cells were sorted and analyzed uniformly for telomere length using qPCR. Based on the quartiles of donor telomere length, patients were categorized into the shortest telomere group (Q1), intermediate length telomere group (Q2, Q3), and longest telomere group (Q4), and the transplant outcomes were compared among the different telomere length groups. Results Out of the 863 eligible patients, 137 underwent allo-HSCT with matched sibling donors, 88 with unrelated donors, and 638 with haploidentical related donors. There were 546 donors aged < 40 years and 317 donors aged ≥ 40 years. An inverse linear correlation was observed between donor age and telomere length (P < 0.001, Figure 1A). However, this age-dependent association was mainly evident in younger donors (age < 40 years, P = 0.021), while in donors aged ≥ 40 years (elderly donors), it did not reach statistical significance as observed in the younger donor group (P = 0.36). In patients receiving grafts from younger donors, there was no significant correlation between telomere length and engraftment, acute graft-versus-host disease (aGVHD), chronic graft-versus-host disease (cGVHD), non-relapse mortality (NRM), relapse, relapse-free survival (RFS), or overall survival (OS). In patients receiving grafts from elderly donors, the shortest telomere length was associated with an elevated incidence of aGVHD, while aGVHD incidence was similar between intermediate and longest telomere groups (49.4%, 38.5%, and 34.2% for shortest, intermediate, and longest, respectively, P = 0.06). Moreover, the intermediate telomere group exhibited improved OS (3-year OS for shortest, intermediate, and longest was 59.2%, 75.6%, and 59.9%, respectively, P = 0.07, Figure 1B) and prolonged RFS (3-year RFS for shortest, intermediate, and longest was 58.8%, 74.1%, and 55.1%, respectively, P = 0.06, Figure 1C). While the donor age has on impact on OS and RFS (P > 0.05). Even after adjusting for prognostic factors such as patient age, pre-transplant disease status, disease risk index stratification, and transplantation type, the multivariate analyses consistently indicated that intermediate telomere length remained an independent protective factor for OS (HR = 0.549, 95% CI, 0.328-0.920, P = 0.023, Figure 1D) and RFS (HR = 0.591, 95% CI, 0.361-0.967, P = 0.036, Figure 1E). Notably, elderly donors with the longest and shortest telomeres showed significantly inferior OS compared to younger donors ( Figure 1F). However, those elderly donors with intermediate telomere lengths demonstrated comparable OS to younger donors ( Figure 1G). Conclusion This study has significantly advanced our comprehension of telomeres, revealing that both excessively long and short telomeres are linked to adverse clinical outcomes in allo-HSCT for acute leukemia. Remarkably, elderly donors with intermediate-length telomeres demonstrate comparable outcomes to younger donors, challenging the conception that “young donors are superior to elderly donors.” These findings underscore the paramount importance of donor telomere length more than donor age, emphasizing its pivotal role in allo-HSCT success.

Inflammatory Signatures Define a New High-Risk T-Lineage ALL Subtype

T-lineage acute lymphoblastic leukemia (ALL) is an aggressive cancer comprising of diverse subtypes that are challenging to stratify using conventional immunophenotyping and have historically exhibited poor treatment outcomes in response to cytotoxic chemotherapy ( Nguyen, K et al. Leukemia 2008). Early T-cell Precursor ALL (ETP-ALL) represent a distinct subtype that displays a developmental block at the earliest stages of T-cell commitment, accompanied by the aberrant expression of myeloid and stem cell markers ( Coustan-Smith, E. et al. Lancet Oncol. 2009). The classification can be further complicated by T/Myeloid Mixed phenotype acute leukemia (T/My-MPAL), a rare and aggressive malignancy characterized by blasts with both T-cell lymphoid and myeloid markers ( George, B. S. et al. Biomedicines 2022). Accurate clinical diagnosis of T-lineage ALL is hindered by phenotypic variations among its subsets. Nevertheless, the precise diagnosis holds critical importance as drug sensitivity in preclinical models of T-lineage ALL is closely linked to the differentiation state, such as the sensitivity of ETP-ALL to the BCL-2 inhibitor venetoclax ( Chonghaile, T. N. et al. Nat Cancer 2021). This highlights the critical need to identify consistent phenotypic traits associated with unique therapeutic vulnerabilities to effectively tailor therapy to individual patients. To gain insights into subset-specific therapeutic vulnerabilities, we performed an integrative multiomic analysis of bone marrow (BM) samples (n=21) from newly diagnosed T-lineage ALL patients, including T-cell ALL (T-ALL), ETP-ALL, and T/My-MPAL. Leveraging cellular indexing of transcriptomes and epitopes in conjunction with T-cell receptor sequencing, we identified a distinct subset of patients spanning all three subtypes characterized by the high frequency of leukemic cells that most closely resemble healthy hematopoietic stem and progenitor cells (HSPC) by Symphony ( Kang, J. B. et al. Nat Commun 2021) query mapping, indicative of an earlier stage of differentiation arrest ( Figure 1A bottom). Pathway analysis revealed an inflammatory signature in patients with high frequencies of stem-like cells suggestive of an inflammatory microenvironment akin to high-risk AML ( Lasry, A. et al. Nat Cancer 2023), which we refer to as inflammatory T-lineage ALL. Next, we mined our multiomic data to generate a comprehensive geneset for inflammatory T-lineage ALL scoring in single cells and bulk samples ( Figure 1A top). Interestingly, Olink cytokine array analysis uncovered upregulation of production of cytokines IL-1β, IL-18, and/or OSM in inflammatory T-lineage ALL samples. Thus, this comprehensive multiomic analysis identified a subset of T-lineage ALL patients characterized by early differentiation arrest and inflammatory signatures. To explore the relationship between inflammatory T-lineage status and clinical response, we utilized the ssGSEA algorithm to score activity of our inflammatory signature in bulk RNA-sequencing data from the TARGET T-lineage ALL dataset (n=265, 74/265 inflammatory) ( Liu, Y. et al. Nat Genet 2017) and the Tran et al. study (n=27, 17/27 inflammatory) ( Tran, T. H. et al. Blood Adv 2022). We found a significant association between high inflammatory ssGSEA score and elevated MRD. To uncover the inflammatory T-lineage ALL mutational landscape, we performed whole exome sequencing on our study cohort, and compiled the reported mutations in the TARGET dataset. Interestingly, inflammatory T-lineage ALL patients, as predicted by inflammatory signature activity, had a significantly higher prevalence of mutations affecting cytokine signaling ( NRAS, JAK3), chromatin remodeling genes ( EZH2), and the WT1 oncogene. These analyses demonstrate a significant relationship between inflammatory status, genomic lesions, and MRD. Finally, we demonstrate that inflammatory, but not non-inflammatory, T-lineage ALL cells are significantly more sensitive to BCL-2 inhibitor venetoclax ex vivo (Figure 1B).Overall, our study has identified a new subtype of T-lineage ALL defined by an early arrest in T-cell development, inflammatory signaling, a unique mutational landscape, sensitivity to venetoclax, and an association with adverse clinical parameters.

Array CGH + SNP in ALL Enhances Detection of Complex Cytogenetic Profiles and Suggests That PRSS1 Loss May Play a Role in Leukemogenesis

Introduction Cytogenetic alterations are essential prognostic biomarkers in patients (pts) with acute lymphoblastic leukemia/lymphoma (ALL), but are limited by the propensity of leukemic blasts to undergo apoptosis in culture, poor-quality chromosomes, and overgrowth by normal cells. Array CGH + SNP has 10,000-fold higher resolution than conventional cytogenetics and can identify submicroscopic gains, losses and copy number neutral loss of heterozygosity (cnLOH) irrespective of mitotic rate. Few studies outside of clinical trials have investigated microarray findings in adults with ALL or correlated microarray findings with clinical outcomes. Methods We retrospectively reviewed pts with ALL and mixed phenotype acute leukemia (MPAL) aged ≥18 years at diagnosis at our institution between 2017 and 2022. Array analysis was performed on diagnostic bone marrow or peripheral blood samples using high resolution CGH + SNP Genetisure cancer array platform (Agilent). Statistical analysis was done using R software (R core team, 2022). Results Baseline characteristics of included pts (n = 60) are shown in Table 1. CGH + SNP analysis identified 93.3% (56/60) of pts with genomic changes with a mean of 7 (range 0 - 28) aberrations per pt. Among pts with a normal karyotype, 81.8% (9/11) had new genomic abnormalities revealed by CGH + SNP, but significantly fewer aberrations were detected per pt compared to those with abnormal karyotypes (mean 3.09 v. 7.67, p = .008). Pts with Ph-like B-ALL/MPAL had significantly more aberrations on array than pts without Ph-like phenotype (mean 12.0 v. 5.85, p.= .002). Among the 78.3% of pts without complex cytogenetics on chromosome analysis, 44.7% (21/47) were found to have a complex genomic profile (≥5 aberrations) with the addition of CGH + SNP. However, there was no difference in CR rates or OS in pts with <5 or ≥5 microarray aberrations (p = .515 and p = .970, respectively). Quantity of copy number alterations (CNAs) as detected on array was not predictive of achieving end of induction CR/CRi/CRh (mean 6.08 in pts who achieved CR/CRi/CRh v. 7.02 in pts with primary refractory disease, p = .310). Hispanic pts had the same number of CNAs as non-Hispanic pts (mean 6.69 v. 6.94, p = .435). On linear regression analysis, there was no correlation between number of CNAs and age (r 2 = -.01, F = 0.1941, p = .661) or BMI (r 2 = 5.21 x10 -5, F = 0.0029, p = .957). The most frequent focal aberrations were detected in CDKN2A/B (n = 19), IKZF1 (n = 17), PRSS1 (n = 11), PAX5 (n = 8), BTG1 (n = 8) and RB1 (n = 8) (Figure 1). RB1 loss was enriched in pts with T-ALL (45.5% v. 6%, p = .003),and occurred at significantly higher rates than previously reported in T-ALL (Schraders, 2009). Loss of PRSS1 was detected in 18.3% (11/60) of the cohort. Homozygous PRSS1 deletions were identified in 3/11 (27.3%) pts. We identified the minimal overlapping deleted region on 7q34 in all 11 pts, which included the PRSS1 gene within the 124 kb region. Five of 6 pts who had repeat arrays performed at the end of induction had resolution of this aberration. The one pt who retained PRSS1 loss after induction had primary refractory disease, but after further treatment and attainment of CR1, this pt cleared the PRSS1 loss. Asparaginase associated pancreatitis, which has been linked to PRSS1 variations, occurred in only 1 pt with PRSS1 loss. Pts harboring PRSS1 loss were significantly less likely to achieve MRD negativity after induction (50% vs. 82%, P = .041) and had numerically more relapses (37.5% vs. 19%, p = .300), but no OS difference was observed (p = .290). Conclusions In our institutional cohort, the addition of CGH + SNP array reclassified almost half (44.7%) of pts without complex cytogenetics to harbor complex genomic changes (≥5 aberrations). Pts with Ph-like ALL had significantly more aberrations on array than those with Ph-positive or -negative B-ALL. Focal PRSS1 loss was associated with reduced rates of MRD clearance at the end of induction. This aberration resolved upon disease remission, raising the possibility that both homozygous and/or heterozygous deletions of 124 kb from the 7q34 chromosomal region of the PRSS1 gene may potentially have a role in ALL pathogenesis. Further studies with larger cohorts utilizing CGH + SNP analyses at additional time points during treatment are needed to explore the potential integration of microarray data for refined ALL risk stratification as well as to elucidate the functional role of PRSS1 in leukemogenesis.

Incidence and Risk Factors for Central Nervous System Relapse after Allogeneic Hematopoietic Stem Cell Transplantation in Adult Patients with Acute Lymphoblastic Leukemia

Background Acute lymphoblastic leukemia (ALL) is frequently accompanied with the involvement of the central nervous system (CNS). The clinical prognosis for ALL patients with CNS disease is generally unfavorable, and prophylactic measures such as intrathecal chemotherapy are highly recommended. In adult ALL patients, hematopoietic stem cell transplantation (HSCT) presents a potential curative approach. However, there are currently only a few reports available on the risk factors and epidemiology of CNS relapse after HSCT. Method We conducted a retrospective single-center cohort study involving 1043 patients diagnosed with either acute lymphoblastic leukemia (ALL) or mixed phenotype acute leukemia (MPAL). These patients were treated at our center using the same treatment protocol between 2009 and 2022. During the remission induction phase, we utilized a modified hyper-CVAD regimen, along with six rounds of prophylactic intrathecal (IT) chemotherapy. High-risk patients who had suitable donors underwent allogeneic hematopoietic stem cell transplantation (HSCT) as part of their post-remission therapy. Diagnosis of central nervous system (CNS) leukemia was established when neurologic symptoms were observed in correlation with CNS lesions on imaging studies, or when leukemic blasts were detected in the cerebrospinal fluid (CSF). In our study, we examined the incidence, risk factors, and survival outcomes of patients who experienced CNS relapse after transplantation. Results Among the entire cohort of 1043 patients, CNS involvement was observed in 3 (0.3%) patients at initial diagnosis and 12 (1.2%) during chemotherapy. We proceeded with allogeneic hematopoietic stem cell transplantation (allo-HSCT) in 755 consecutive patients. Among these 755 patients, 3 had CNS leukemia prior to transplantation. Among the group of 755 patients, a total of 224 (29.6%) experienced relapse. Of these relapses, 142 (18.8%) were bone marrow relapses alone, 54 (7.1%) were extramedullary relapses alone (with CNS involvement in 21 [38.8%]), and 28 (3.7%) had both bone marrow and extramedullary relapses (with CNS involvement in 13 [46.4%]). Overall, extramedullary relapse was observed in 82 (10.8%) patients, with CNS involvement in 34 (4.5%) cases, following allo-HSCT. The 5-year cumulative incidence of CNS relapse was 4.6%, which was significantly higher in patients with Philadelphia chromosome-positive (Ph-positive) ALL (9.4% vs. 1.0%, p <0.001), as well as those with a high leukocyte count at diagnosis (8.3% vs. 2.6%, p = 0.001). Among the Ph-positive ALL cases, a high leukocyte count (n=151) was associated with a higher prevalence of pre-HSCT minimal residual disease (MRD) > 0.1% (n=88), which exhibited a significantly increased incidence of CNS relapse (16.6% vs. 6.8%, p = 0.009). Factors such as age, number of intrathecal chemotherapy treatments, conditioning intensity, and dose of anti-thymocyte globulin did not have a significant impact. Among the 34 patients with CNS relapse, 21 (61.7%) had isolated CNS relapse, and 7 of them showed evidence of positive MRD. With the exception of one patient who refused further treatment, the remaining 33 patients received initial CNS local therapy, including intrathecal chemotherapy combined with radiotherapy in 27 (82.0%) cases, intrathecal chemotherapy alone in 6 cases, and radiotherapy alone in 4 cases. Out of these patients, 22 were treated with dasatinib or ponatinib, while 6 received salvage chemotherapy. The median overall survival for patients with CNS relapse was 11.2 months, which was 19.8 months for those with isolated CNS relapse and 10.9 months for those with CNS relapse accompanied by bone marrow relapse (p = 0.077). The subsequent 2-year cumulative incidence of CNS relapse was 30%. Conclusion Based on our findings, the current prophylaxis strategy employed for the prevention of post-HSCT CNS relapse in adult ALL appears to be effective. However, our data indicates that MRD-positive Ph-positive ALL requires distinct management due to its significantly elevated risk of CNS relapse. New strategies including prophylactic radiotherapy for this high-risk subgroup must be considered to prevent post-HSCT CNS disease.

Recurrence of HBV Reactivation after Allogeneic Hematopoietic Transplantation in Recipients with Resolved HBV Infection: A Nation-Wide Multicenter Retrospective Study

Introduction Reactivation of hepatitis B virus (HBV) is known to cause fulminant hepatitis after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in recipients with resolved HBV infection. Monitoring of HBV-DNA and HBV-DNA-guided preemptive therapy using nucleotide analogue (NA) is recommended to prevent developing hepatitis due to HBV reactivation after allo-HSCT. However, little is known about the adequate duration of NA treatment and the frequency of the recurrence of HBV reactivation (2nd HBV reactivation) after discontinuation of NA. We conducted a nationwide retrospective study of HBV reactivation after allo- HSCT. Patients and Methods We retrospectively reviewed the clinical information of recipients with resolved HBV infection (HBsAg-negative, anti-HBc-positive) before allo-HSCT and were diagnosed as HBV reactivation (HBsAg and/or HBV-DNA positive) after allo-HSCT from January 2010 to December 2020. Patients who received prophylactic NA before HBV reactivation were excluded. This study was approved by the Hokkaido University Hospital institutional review boards and registered as UMIN 000046803. Results A total of 72 patients were enrolled (median age of 60 years, range, 27-73 years; 42 males and 30 females) from 16 institutions. Initial hematological diseases were acute myeloid leukemia 21, myelodysplastic syndrome 14, chronic myeloid leukemia 4, acute lymphoblastic leukemia 12, non-Hodgkin lymphoma 8, adult T cell leukemia-lymphoma 6, mixed phenotype acute leukemia 4, and others 3. HSCT details were as follows: donor source, unrelated bone marrow 33, cord blood 24, related peripheral blood 11, unrelated peripheral blood 4; acute graft versus host disease (GVHD) 48 (66.7%); chronic GVHD 44 (61.1%); systemic steroid usage 41 (56.9%). Initial HBV reactivation after allo-HSCT was observed on day 10-3034 (median 512.5). Immunosuppressants and systemic steroids were administered in 35 (48.6%) and 28 (38.9%) patients respectively at the time of HBV reactivation. The patients who showed anti-HBs below protection levels (<10mIL/mL) were 18 (25%) of 72 patients at pre-HSCT, however, the number increased to 35 (81.4%) of 43 patients who were analyzed at the point of HBV reactivation after allo-HSCT. All patients received preemptive NA (entecavir 65, tenofovir alafenamide 6, tenofovir 1). Elevated aspartate transaminase of more than 200 U/L was observed in 7 cases at HBV reactivation, and all of them showed HBV-DNA more than 4 Log IU/mL. No one developed fulminant hepatitis but 5 patients resulted in continuous HBV carriers. Twenty-four of 72 patients were discontinued NA by each physician's decision. Of 24 patients who discontinued NA, 11 (45.8%) patients developed 2 nd HBV reactivation. The median duration from discontinuation of NA to 2 nd HBV reactivation was 113 days (range, 15 to 434). Duration of initial NA administration was not significantly different between patients with 2 ndHBV reactivation and those without 2 nd HBV reactivation (90-1968 days, median 553 vs 145-3734 days, median 861; p=0.11). In those who analyzed anti-HBs at discontinuation of NA, 4 of 8 cases (50.0%) with anti-HBs <10 mIU/mL developed 2 nd HBV reactivation, whereas only 1 of 6 cases (16.7%) with anti-HBs >10 mIU/mL developed 2 nd HBV reactivation. Four of the 11 cases with 2 nd HBV reactivation were attempted rechallenge of NA discontinuation, however, all 4 cases developed 3 rd HBV reactivation on day 28-127 after discontinuation of NA. These 4 cases further developed 4 th HBV reactivation after the rechallenge of discontinuation of NA. One patient developed protective anti-HBs titer after 2 courses of HB vaccination, and finally successfully discontinue the NA after 4 th HBV reactivation. The patient did not develop further reactivation for more than 3 years. Conclusion 2 nd reactivation of HBV after NA discontinuation was common in patients with HBV reactivation who received allo-HSCT despite the long duration of NA. Acquisition of anti-HBs by HBV reactivation itself or HB vaccine would be necessary to suppress further HBV reactivation. Careful monitoring of HBV-DNA is important even after the discontinuation of NA in the case with HBV reactivation after allo-HSCT because multiple reactivations could occur. A prospective randomized trial of the HB vaccine after allo-HSCT for preventing HBV reactivation is now ongoing (UMIN000034113).

Canadian Cancer Trials Group SC.26 - Emotion and Symptom-Focused Engagement (EASE): A Multi-Site Randomized Controlled Trial of an Intervention for Individuals with Acute Leukemia

Background: Despite the rapid onset and life-threatening nature of acute leukemia (AL) and its treatment, there is a lack of research on its psychological and physical consequences and even less on interventions to alleviate them [Bryant 2016]. A longitudinal study of individuals with newly diagnosed or recently relapsed AL showed substantial physical and psychological distress in this population [Rodin 2013; Zimmermann 2013]. Based on these findings, an integrated psychosocial and early palliative care intervention, Emotion And Symptom-focused Engagement (EASE), was developed for patients with AL [Rodin 2015]. A phase II randomized pilot trial of EASE vs. usual care demonstrated feasibility and showed promising positive effects on traumatic stress symptoms (primary outcome) and other secondary outcomes, including depressive symptoms, number and severity of physical symptoms and related distress, pain, quality of life (QOL), satisfaction with care, and attachment security [Rodin 2020]. Study design and methods:The Canadian Cancer Trials Group SC.26 (NCT04224974) randomized phase III trial is underway to test the effectiveness and cost-effectiveness of the EASE intervention in AL. EASE is a novel manualized intervention that combines psychological support with routine symptom screening plus triggered referral to palliative care for symptom control. The goal is to reduce psychological distress and symptom burden, and enhance QOL and satisfaction with care in individuals with newly diagnosed AL undergoing induction therapy. Participants are randomized in a 1:1 unblinded ratio to usual care (UC) or UC and EASE (EASE). EASE consists of two components: the psychotherapy intervention (EASE-psy) and triggered early palliative care (EASE-phys). EASE-psy involves tailored supportive psychotherapy delivered by trained therapists over the initial 8 weeks following hospital admission for treatment of AL. It combines elements of relational support, affect regulation, and trauma-informed cognitive behavioural therapy. All patients randomized to EASE receive weekly symptom screening during the initial inpatient treatment period with triggered referral to early palliative care (EASE-phys). Subjects are stratified by centre, age (≤60 vs. >60) and type of acute leukemia (acute myeloid leukemia vs. acute lymphoblastic leukemia). For patients diagnosed with a mixed phenotype acute leukemia, the dominant sub-type is used for stratification purposes. Patients are ≥18 years, newly diagnosed and recruited within 2 weeks of hospital admission, and receiving or expected to receive induction therapy with curative intent. Current exclusion criteria include major communication difficulties at the time of recruitment; receipt of on-site psychological/psychiatric counselling or palliative care services at the time of recruitment; a diagnosis of acute promyelocytic leukemia or acute leukemia of ambiguous lineage. The two primary outcomes reflect the dual nature of the physical and psychosocial components of the EASE intervention: Mean severity of traumatic stress symptoms at 4 weeks using the 30-item Stanford Acute Stress Reaction Questionnaire (SASRQ) [Cardeña 1996] updated to be DSM-5-concordant [American Psychiatric Association 2013] and mean physical symptom severity at 4 weeks using the Memorial Symptom Assessment Scale (MSAS) [Portenoy 1994]. Hypotheses will be tested using multilevel modeling with maximum likelihood estimation, conducted as intention-to-treat analyses. Economic analysis will be conducted to measure the cost-effectiveness of the EASE intervention. Utilities will be derived from the EQ-5D-5L [Herdman 2011] and FACIT-Sp [Webster 2003] questionnaires. The planned sample size of this study is 266. Since January 2022, 53 patients at 4 Canadian centres have undergone randomization. Conclusion: The information obtained from this study will inform clinicians and decision makers of the value of implementing the EASE intervention in adults with AL.

Assessment of Optical Genome Mapping for Front-Line Diagnostic Evaluation of Acute Leukemia: A Canadian Single-Center Evaluation of Added Yield in 69 Informative Cases

Optical genome mapping (OGM) is a novel method currently being evaluated internationally as a diagnostic assay for genomic profiling of malignancies. OGM uses imaging and reference alignment of fluorescently labeled ultra-long DNA molecules to detect structural and copy number variants genome-wide at significantly higher resolution than is attainable with current standard-of-care (SOC) cytogenetic analysis. OGM is nearing deployment as a first-line diagnostic test for patients with acute leukemia at Vancouver General Hospital, the largest tertiary care hospital in British Columbia. Here, we describe our experience in the evaluation of OGM as a diagnostic assay relative to SOC karyotyping and fluorescence in situ hybridization (FISH) in newly diagnosed and relapsed acute leukemia. A selected cohort of 69 bone marrow specimens produced adequate quality OGM data for analysis: 52 acute myeloid leukemia (AML), 12 B-lymphoblastic leukemia (B-ALL), 4 mixed phenotype acute leukemia (MPAL; 2 B/myeloid, 1 B/T, and 1 T/myeloid), and 1 blast phase (T) myeloid/lymphoid neoplasm with tyrosine kinase gene fusion (M/L-N-Eo). Variants were filtered using population thresholds and with pan-cancer (669 genes) and disease targeted (myeloid: 185; B-lymphoid: 130) gene lists to facilitate detection of variants of interest. OGM results were compared to SOC to identify additional diagnostic yield and changes to risk stratification or diagnosis resulting from OGM findings. In these 69 acute leukemias, filtering to remove common polymorphisms using a manufacturer-provided control dataset yielded a median of 53 variants (interquartile range (IQR) 39-86); using a pan-cancer list yielded a median of 6 (IQR 2-16); and disease-specific lists a median of 4 (IQR 1-10.5). In 11% of cases, diagnosis or risk stratification was altered by OGM (13% of AML; 8% of B-ALL), including a complex karyotype being resolved as normal, downgrading cytogenetic risk; identification of several cryptic KMT2A rearrangements, changing diagnostic classification; and identification of cryptic MECOM::RUNX1 (class-modifying), NUP98::NSD1 (risk-upgrading), and NUP214::ABL1 (potentially targetable and class- and risk-modifying) fusions. In 26% of cases, driver rearrangements were either newly identified by OGM or novel partner genes were resolved (23% of AML; 33% of B-ALL; 40% of others), including recurrent rearrangements of the IGH locus with MIR125B1/ BLID in B-ALL; KMT2A partial tandem duplication; novel MECOM::PAN3, JAKMIP2::PDGFRB, and NUP214::FRMD4B fusions; and a cryptic deletion juxtaposing FLT3 and PAN3 known to result in FLT3 overexpression. Additional findings, including copy number changes and clarifications of complex events, were seen in 54% of cases (44% of AML; 83% of B-ALL; 80% of others), mostly accounted for by small deletions or disruptive rearrangements in key disease genes,likely resulting in loss of function, including but not limited to RUNX1, GATA2 and ETV6 in AML; CDKN2A, PAX5, and RB1 in B-ALL; and TP53 in MPAL. Several cases harboured small MLLT4 copy number abnormalities that have been reported to be linked to cancer predisposition, and one potentially germline FANCA deletion was observed. Details of comparison between SOC methods (karyotyping and pertinent FISH where applicable) are detailed in the Figure and Table (bold text: newly resolved or clarified potential driver or resolution of normal karyotype; underline: change in diagnosis or risk stratification resulting from OGM findings). Notably, OGM failed to identify one hypodiploid B-ALL clone masked by endoreduplication, and further evaluation of this technology's performance in this context and in prospective practice is required. This study demonstrates the significant potential added diagnostic yield of OGM relative to SOC as a clinical diagnostic and research assay. High-resolution genome-wide evaluation not reliant on cell culture substantially expands the scope of detectable variants, for many of which determining the biologic and clinical implications will require larger scale prospective study. Importantly, application of OGM in the clinical setting is likely to result in clinically meaningful disease reclassification and restratification of risk, and in some cases may permit patients access to previously inaccessible targeted therapies (as in the instance of cytogenetically cryptic tyrosine kinase gene fusions).

Blinatumomab in Combination with Immune Checkpoint Inhibitors (ICIs) of PD-1 and CTLA-4 in Adult Patients with Relapsed/Refractory (R/R) CD19 Positive B-Cell Acute Lymphoblastic Leukemia (ALL): Results of a Phase I Study

Background: Blinatumomab (blina) improves outcomes in R/R CD19+ ALL compared to chemotherapy. However, the overall response rate to blina was 44%, and median overall survival (OS) is just 7.7 mos (Kantarjian. NEJM. 2017). Preclinical studies show increased PD-L1 expression on leukemic blasts potentially contributes to relapse after blina. The addition of PD-1 +/- CTLA-4 blockade to blina leads to increased in vitro T cell proliferation and enhanced cytotoxicity (Feucht. Oncotarget 2016). Thus, blockade of co-inhibitory pathways may enhance blina efficacy in vivo. We describe results of a multi-center phase I study combining blina with immune checkpoint inhibitors (ICIs) targeting PD-1 (nivolumab) +/- CTLA-4 (ipilimumab). Methods: In a dose-escalation study, we evaluated the safety, tolerability, and preliminary efficacy of blina with nivolumab (nivo) +/- ipilimumab (ipi) using a 3+3 design. Pts ³16 years-old with R/R CD19+ B-ALL or mixed phenotype acute leukemia (MPAL) were eligible. Pts ³60 years could be untreated. Table 1 presents the dose escalation schema. Expansion cohorts of 6 pts were planned at the maximum tolerated dose (MTD) for blina + nivo AND blina + nivo + ipi. Pts received up to 5 cycles of blina and 1 year of ICIs. Pts removed from the study during the blina lead-in (days 1-10) were replaced. Dose-limiting toxicities (DLTs) were defined as grade 3+ non-hematologic toxicities requiring the permanent discontinuation of treatment in the first 42 days. Primary endpoints were toxicities and MTD. Secondary endpoints included complete remission (CR), MRD-negativity at a sensitivity of 0.01%, duration of response and OS from treatment initiation. Results: Twenty-seven pts were enrolled to 3 dose levels (14 DLA1, 3 DLB1, and 10 DLB-1) from September 2017-December 2022. Six pts were replaced (4 prior to ICI dosing and 2 requiring subsequent therapy in the DLT window). The median age of enrolled pts was 55 (range 24-84), 14 were male (52%), and median baseline BM blasts were 60% (range 0.2-98%). Baseline characteristics are presented in Table 2. A single DLT (G4 infusion reaction and G3 hypotension) occurred among 6 pts at DLA1. Based on this safety and efficacy data, blina + nivo was expanded to include 6 additional pts without additional DLTs. There were 2 DLTs at DLB1 (G5 pneumonitis and G2 GVHD), which led to de-escalation to DLB-1, where there was 1 DLT (G3 delirium). Grade 2+ immune-related adverse events attributable to ICIs included pneumonitis (G2+G5), rash (G2+G3), transaminitis (G2+G3), colitis (G3), and hypothyroidism (G2). Grade 3+ adverse events attributable to blina included neutropenia (5-G4+3-G3), dysphasia (2-G3), weakness (G3), seizure (G4), and transaminitis (1-G4+4-G3). Among 22 pts evaluable for response, the CR rate was 68% (100% MRD-negative). Among 13 pts with >50% BM blasts at baseline, 62% achieved CR. Pts with B-myeloid MPAL (0/2) and a history of extramedullary disease (1/4) were less likely to respond. Nine responders subsequently relapsed including 3 with isolated extramedullary disease and 2 with CD19-negative disease. As shown in Figure 1, relapse-free survival (RFS) at 1 year was 27% (95% CI 10-46), while OS at 1 year was 63% (95% CI 38-79). Twelve pts underwent allogeneic blood or marrow transplant (alloBMT) following study treatment. At 1 year for alloBMT pts, RFS was 51% (95% CI 19-76) and OS was 61% (95% CI 26-83). Ongoing analyses of changes in T cell subpopulations, co-signaling molecule expression, and single cell RNA seq results will be presented. Conclusions: Combination therapy with blina and ICIs in R/R ALL is safe, feasible, and associated with a high MRD-negative response rate. Long-term survival was promising in comparison to prior results with blina monotherapy, especially following consolidation with alloBMT. A randomized trial of blina +/- nivolumab is needed to confirm the benefit of this combination.

Transcription Factor GATA2 Is Inevitable for the Survival and Proper Differentiation of Thymic Multipotent Progenitor Cells By Gene Expression Orchestration

Proper differentiation of T cells in the thymus is inevitable for the establishment of acquired immunity. Lymphoid-primed multipotent progenitors (LMPPs) emigrate from the bone marrow (BM) to the thymus for becoming earliest T cell progenitors, so-called early T cell progenitors (ETPs). Previous studies have shown that ETPs retain not only T cell but also innate immune cell (i.e., myeloid cells) differentiation potentials. Therefore, ETPs might be the bifurcation point of innate and adaptive immunity in thymus. However, still little is known about the mechanism by which the differentiation fates are determined in ETPs and the cellular heterogeneity in ETP subset. Since transcription factors that possess important roles in hematopoietic stem and progenitor cells (HSPCs) may play significant roles in the early differentiation of T cells as legacy stem cell genes, we sought to investigate the roles for GATA2, which is known to regulate the HSPC maintenance and myeloid differentiation, in ETPs. First, we revealed the GATA2 expression is preserved in ETPs and sharply disappear with their differentiation (GATA2 expressions were almost undetectable from double-negative 2 cells even by qPCR). To reveal the roles for GATA2 in T cell hematopoiesis, we analyzed Gata2 fl/fl; Mx1-Cre mice in which GATA2 was deletable in hematopoietic cells by polyI:C administration ( Gata2 KO). Gata2 KO mice showed a smaller thymus and a lower number of thymic T cells, including ETPs and double-positive (DP; CD4 +CD8 +) cells, than control. To rule out contributions of potential GATA2 deletions in non-hematopoietic cells, CD45.1 + wild-type unfractionated BM cells were transplanted into Gata2 KO or control mice. There were no particular differences in T cell hematopoiesis from CD45.1 + donor cells between them, supporting the notion that hematopoietic cell intrinsic GATA2 are inevitable for the proper T cell hematopoiesis. To further reveal the roles for GATA2 in ETPs, we performed global transcriptomic analysis of ETPs (RNA-seq; Gata2 KO vs control). Gene set enrichment analysis (GSEA) revealed that signatures associated with cell cycle regulation, hematopoietic progenitor cells and myeloid cells were down-regulated in Gata2 KO ETPs, suggesting that GATA2 is involved in the survival and myeloid differentiation potentials in ETPs. By taking the advantage of novel GATA2 reporter mice (GATA2-VENUS mice) in which GATA2 protein levels are detectable by flow cytometry, we revealed that the ETP fraction contained a mixture of cells with high or low GATA2 expression. To be noted, the protein expression intensity of GATA2 in GATA2-high ETPs was almost equivalent to that of LMPPs. These observations suggest that GATA2-high ETPs might be a thymic multipotent progenitors (T-MPPs), the earliest thymic progenitors in which T or myeloid cell differentiation commitment is defined. To elucidate the mechanism by which GATA2 regulates the survival and differentiation of T-MPPs, we integrated publicly available chromatin immunoprecipitation followed by sequencing data targeting GATA2 (GATA2 ChIP-seq) and our ETP RNA-seq data. We found several key genes in HSPCs maintenance (i.e. Lyl1) or myeloid differentiation (i.e. Itga2b) as potential targets of GATA2. Furthermore, we sought to reveal the effect of GATA2 deletion in progenitor cells to their progenies. To this end, we performed RNA-seq of DP cells ( Gata2 KO vs control). GSEA revealed that cell cycle related gene signature was repressed in Gata2 KO DP cells compared to control. To be noted, in CD4-Cre dependent GATA2 deletion model ( Gata2 fl/fl:CD4-Cre mice), there were almost no particular cell number and transcriptomic differences, which was also analyzed by RNA-seq, in DP cells compared to control. These results suggest that GATA2 in GATA2-high ETPs, but not in DP cells, may affect the feature of DP cells, potentially by epigenetic memory. Collectively, this study revealed that GATA2 contributes to T cell hematopoiesis. GATA2 expression was maintained in a part of the ETP subset (GATA2-high ETPs) which might be equivalent to T-MPPs. GATA2 may affect the differentiation trajectory and function from GATA2-high ETPs to their progenies. Further study of this mechanism will help us to understand how the acquired and innate immune bifurcation is defined, which might pave the way to overcome T cell development related disorders, such as T-cell/myeloid mixed-phenotype acute leukemia.

Chidamide-Based Pre-Emptive Treatment for High-Risk AML Patients after Hematopoietic Stem Cell Transplantation: A Real-World Experience from Chinese Single-Center

Background: The treatment of relapsed or refractory acute myeloid leukemia ( AML) remains challenging. Measurable residual disease (MRD) persistence at transplantation or post-transplantation has been identified as the strongest risk factor for relapse and poor outcomes for patients with hematological malignancies (HMs). Chidamide, a novel oral histone deacetylase inhibitor, has shown potential therapeutic effects in various types of HMs by inducing cell apoptosis and regulating immunity. This study aimed to evaluate the efficacy and safety of Chidamide-based prophylactic or pre-emptive treatment for patients who are MRD positive before or who have sustained MRD positive after transplantation. Aim: The rate of 6 months of conversion to MRD- and relapse-free survival of high-risk AML after Chidamide-based treatment. Methods: From December 2020 to July 2023, 50 patients with high-risk HMs received chidamide-based therapy after allo-HSCT. 39 patients were diagnosed with AML ( 4 secondary AML), 2 with myelodysplastic syndromes, 6 with acute lymphoid leukemia, and 3 with mixed-phenotype acute leukemia. 46 patients (92%) with relapsed/refractory status or detectable MRD (MRD+) at transplantation or after allo-HSCT received chidamide as pre-emptive, and the remaining 4 high-risk patients with MRD− conducted as prophylactic intervention. Patients with detectable MRD before transplantation and those who remained positive for MRD after transplantation were defined as very high-risk AML (VHR-AML). Chidamide was administered at a dose of 5 mg per day orally, 6 times per week, lasting at least 1 year after engraftment. Additional agents included hypomethylating agents (HMAs), donor lymphocyte infusion (DLI) or tyrosine kinase inhibitor (TKI) in patients with Philadelphia chromosome-positive. In this study, 28 patients received chidamide monotherapy, 13 received chidamide combined with HMAs, and 9 cases with other therapy. Results: The median age of all patients was 38 years old (range 17-67), comprising 24 males and 26 females. Up to 1st July 2023, with a median follow-up period of 376 days (25-984d), the overall rate of MRD negative showed 64%. The rate of MRD- survival, Relapse-free survival (RFS) and overall survival (OS) were 56%, 66% and 76%, respectively. The 6 months MRD negative rate, RFS and OS rate were 86%, 82%, 86% and 88%, which maintained at 82%, 82% and 86% with 12 months follow-up, respectively. In 46 cases of the pre-emptive intervention arm, the overall MRD- rate was 61.7%. Among them, 83.3% of patients (20/24) who received chidamide monotherapy exhibited a much higher conversion to MRD− than those combined with HMAs (7/13, 53.8%) or other drugs (2/9, 22.2%) (P=0.004). In 4 cases who received chidamide monotherapy as prophylactic intervention, 3 patients sustained MRD negativity up to the last follow-up, except for one patient diagnosed with MPAL(B+M) relapsed after 1 year of HSCT with taking chidamide for 6 months. A total of 30 patients (including 25 AML) with VHR diseases remained in a status of MRD+ or non-remission after transplantation. Eighteen patients (60%) achieved MRD− and sustained for a median of 251 days (range 31-531 d). VHR-AML patients account for 94.4% (17/18) of MRD- responders(Figure 1A). Similarly, the results showed a higher rate of conversion from MRD+ to MRD− in chidamide monotherapy than the combination groups (Chidamide monotherapy, 81.8%; Chidamide + HMA, 63.6% and Chidamide + others, 25%, P=0.042,Figure 1B). It highlighted that treatment with chidamide resulted in increased MRD− response, especially for AML. On the contrary, of 7 patients with B-cell malignancy, including 5 B-ALL and 2 MPAL (B + M) patients, only 2 (28.6%) patients converted to MRD−. Reversible grade 3/4 neutropenia occurred in 38% of patients, and thrombocytopenia was observed in 24% during the first four treatment cycles. Five patients experienced grade 1/2 non-hematological adverse events, such as fatigue, gastrointestinal reaction, pneumonia and infection. No new-onset GvHD was reported in patients without a prior history of GvHD during chidamide treatment. Conclusion: The chidamide-based regimen is safe and effective in pre-emptive treatment for patients with high-risk relapsed AML after transplantation. Whether as a monotherapy or combined with HMA, chidamide shows significant efficacy in eliminating MRD, warranting further clinical research.

Equity and Resource Allocation: The Case for Allogeneic Transplant in Emergency Medicaid Patients

Background:When an uninsured, undocumented immigrant presents with an emergency medical condition, they may qualify for Emergency Medicaid. Notably, the care and services related to HSCT are not covered, except in California and Washington state. Therefore, many patients with MRD-positive or relapsed ALL who may otherwise be good candidates for HSCT are unable to receive it. This may lead to months of resource-intensive treatment without the chance of cure. Here we present 3 such patients and their course of treatments and outcomes. Patient 1:A28-year-old male from Mexico was diagnosed with Ph+ B-ALL and treated with three cycles of hyper-CVAD + dasatinib. BCR-ABL PCR remained elevated at 27.9% and the patient was switched to nilotinib for 5 more cycles of hyper-CVAD; nilotinib was continued until later relapse. He began maintenance BCNU/cytoxan, then several cycles 6-MP/MTX/vincristine. On day +554 after diagnosis, he relapsed and started decitabine/venetoclax, then decadron + dasatinib, then MVP, followed by 3 cycles of inotuzumab. Later, he started blinatumomab on day +648, which was discontinued after 22 days due to increasing peripheral blasts. He then started SMILE, then CCE. As his condition worsened he was put on ponatinib, then asciminib before expiring on day +940. Patient 2: A37-year-old male from Mexico was diagnosed with CML and started on nilotinib. On day +212 he progressed to lymphoid blast phase CML with CNS involvement and received hyper-CVAD/dasatinib; was switched to nilotinib on cycle 4 due to concerns about pleural effusion while hospitalized for PNA. On day +447 he started blinatumomab + IT MTX + nilotinib. A brain MRI on day +544 suggested carcinomatous meningitis and he got 4 cycles RMVP. He then switched to ponatinib and HiDAC for 8 cycles despite continued ALL in CSF. He was admitted for worsening ALL-induced headache on day +1016 and imaging discovered multifocal pneumonia. He then had seizure-like activity consistent with metabolic encephalopathy and expired on day +1055. Patient 3: A28-year-old male from Ecuador was diagnosed with Ph+ mixed phenotype (B/myeloid) acute leukemia. The patient underwent leukapheresis and started HiDAC + mitoxantrone + etoposide + dasatinib. Subsequent bone marrow biopsy showed 1% blasts, with BCR-ABL PCR at 1.4%. He was admitted on day +170 with Ph+ B-ALL relapse and underwent leukapheresis + 2 cycles hyper-CVAD. On day +255 he began blinatumomab for 3 cycles. He continues to receive treatment for his B-ALL at this time. See table 1 below. Discussion: There is an increasing population of undocumented immigrants entering the United States and receiving treatment for ALL while on emergency Medicaid. It is important to understand the special considerations in this population, including the inability to have HSCT authorized as a treatment option. Studies comparing the costs of HSCT to chemotherapy have found that chemotherapy is cheaper at the expense of patient mortality. Therefore, HSCT's incremental cost-effectiveness ratio, measured as cost per quality-adjusted life years, may still be favorable. As our case series demonstrates, extensive resources including traditional chemotherapies, immunotherapies like blinatumumab, and targeted oral drugs, can further increase the costs relative to HSCT. Moreover, the National Bureau of Economic research has calculated that undocumented workers add about $45,000 per worker to the US GDP annually. Therefore, offering HSCT and allowing them to continue to work may be a reasonable financial option. Likewise, many undocumented adults are the parents of US citizen minors who would benefit economically from their survival. For consideration we will explore cost analysis to further elucidate the potential benefit of allowing coverage of HSCT.

The Influence of Methotrexate-Related Transporter and Metabolizing Enzyme Gene Polymorphisms on Peri-Engraftment Syndrome and Graft-Versus-Host Disease after Haplo-Hematopoietic Stem Cell Transplantation in Pediatric Patients with Malignant Hematological Diseases

Background: Methotrexate (MTX), utilized as a graft-versus-host disease (GvHD) prophylactic agent in allogeneic hematopoietic stem cell transplantation (allo-HSCT), has been proven to effectively decrease the occurrence of the peri-engraftment syndrome (Peri-ES) and acute GvHD (aGvHD). Changes in the pharmacodynamics of MTX are closely associated with gene polymorphisms in genes encoding drug-metabolizing enzymes and transporters. Nevertheless, the current studies mainly concentrate on leukemia or autoimmune diseases, and limited studies on the allo-HSCT were reported. Methods: Here, we retrospectively assessed the relationship between MTX-related transporter and metabolizing enzyme gene polymorphisms, clinical characteristics and outcomes in 57 pediatric patients, who received haploid HSCT (haplo-HSCT), with malignant tumors at a single center. Log-rank test and Cox proportional regression model were used for univariate and multivariate analysis, respectively. A significance level of 0.05 was used for all analyses. Results: At baseline, the mean age at HSCT was 5.1 years old, and more males (80.8%) were enrolled in our cohort. Acute leukemias, including mixed phenotype acute leukemia (MAPL), was the most common etiology, which constituted 94.7% (54/57) of the cohort. All patients achieved hematopoietic recovery from haploidentical donors. The median time to neutrophil and platelet engraftment was 12 days (range, 10-23), 12 days (range, 5-39), respectively. A total of nine kinds of gene polymorphisms were detected and the most common variant type was ABCB1 (1236C>T), followed by MTHFR (665C>T) and ABCB1 (3435C>T). All gene polymorphisms were in Hardy-Weinberg equilibrium in our cohort. We observed the median platelet recovery time of 16 days (range, 10-24 days) for ABCB1 (1236C>T) CC genotype was significantly longer than the median time of 11.5 days (range, 5-39 days) for TC/TT genotype (P = 0.042). In this study, 61.4% of patients (35/57) developed Peri-ES, and 36.8% patients (21/57) developed grade II-IV aGvHD, including 8 (14.0%) with grade II, 8 (19.3%) with grade III, and 5 (8.8%) with grade IV. Compared with SLCO1B1 (1865+4846T>C) TT, patients with SLCO1B1 (1865+4846T>C) TC/CC had the increased incidence of Peri-ES (75.9% vs 46.4%, P = 0.030). Based on the multivariate Cox analysis, we discovered that SLCO1B1 (1865+4846T>C) TT genotype was an independent protective factor for Peri-ES morbidity (hazard ratio (HR)= 0.464; 95% confidence interval (CI)=0.231-0.931; P=0.031). Additionally, when compared with mononuclear cells (MNC) low dose according to the median dose value (cutoff: 6.99×10 8/kg) in our cohort, patients with MNC high dose had the increased incidence of II-IV aGvHD (50.0% vs 24.1%, P = 0.030). Cox regression analysis identified that the dose of MNC reinfused was significantly related with II-IV aGvHD as an independent risk factor in multivariate analysis (HR = 2.604; 95% CI=1.049-6.463; P = 0.039). Unfortunately, no differences was discovered between aGvHD after haplo-HSCT and MTX-related gene polymorphisms. Conclusion: In summary, our findings prove that the host's genotypes might modify the risk of developing Peri-ES, contribute to a better understanding of the inter-individual difference in efficacy, and facilitate the development of individualized approaches to GvHD prophylaxis.

Inotuzumab Ozogamicin in Lymphoid B Cell Malignancy：a Single Center Analysis in the Real World

Background : Recent developments in immunoconjugate usage has changed the landscape of lymphoid B-cell malignancy therapy. Historically, those who relapse from this condition have a dismal prognosis and limited treatment options. One recent development is the inotuzumab ozogamicin (INO), a humanized anti-CD22 monoclonal antibody conjugated to the cytotoxic antibiotic calicheamicin, which has the potential to reduce the overall toxicity of intensive regimens for ALL, as well as to show therapeutic effects in lymphoid B-cell malignancy. Aims and Methods: The study included B cell-acute lymphoblastic leukemia (B-ALL) (n=23), B/ myeloid mixed phenotype acute leukemia (MPAL) (n=1) and B-cell lymphoblastic lymphoma (B-LBL) (n=3) adult patients who received INO in our center from June 2022 to June 2023. Intravenous INO was given 1 or more doses at the dose of 0.6mg/m2, its clinical efficacy and adverse reactions were explored. Results: In our center, INO was strategically employed in various therapeutic scenarios: induction (n=2), maintenance/consolidation (n=6), minimal residual disease (MRD) clearance (n=5), and the management of relapsed/refractory lymphoid B-cell malignancies (n=14). Of the 27 patients, 14 were subjected to a combination regimen of INO and chemotherapy for recurrent and refractory lymphoid B-cell malignancy. The composition of these patients comprised of 4 individuals who experienced a relapse post-standard chemotherapy, 1 patient with a relapse post-allogeneic hematopoietic stem cell transplantation (allo-HSCT), 4 patients with a relapse post-autologous hematopoietic stem cell transplantation (auto-HSCT), and the remaining 5 patients were categorized as refractory cases. The median number of doses administered was 2 (1-3). Complete remission (CR) or CR with incomplete hematologic recovery (CRi) was observed in 9 out of 14 patients (64.3%) within a median duration of 30 (16-78)days. Partial response (PR) was noted in 2 of the 14 patients (14.3%), rendering the overall response rate (ORR) to be 78.6%. Negative MRD was observed in 7 out of 14 patients (50.0%). Of the 9 patients who achieved CR/CRi, 4 (44.4%) relapsed again with 2 fatalities. The remaining 2 patients attained negative MRD following a second allo-HSCT or INO retreatment. The two patients who achieved PR proceeded to receive chimeric antigen receptor T cell (CART) treatment, with one of them subsequently undergoing allo-HSCT after achieving CR. For the three non-responders (NR), one patient unfortunately passed away while the other two patients remained alive and were either participating in clinical trials or undergoing allo-HSCT after CART. For MRD clearance, it was successfully achieved in 4 out of 5 patients (80.0%)treated with INO within a median period of 45 (28-52)days. However, 2 patients reverted to MRD positivity and 1 died. The other four patients underwent allo-HSCT with neither mortality nor recurrence observed. Moreover, two patients (100%) were treated with a VICLP induction regimen combined with INO, with MRD negativity observed post-treatment. Regarding the remaining six patients, three patients were treated with INO as consolidation therapy due to high-risk factors or the intention to undergo auto-HSCT. Another 3 B-ALL patients treated with INO as maintenance therapy after auto-HSCT or after the remission of recurrence after transplantation. One patient unfortunately experienced a second recurrence four months following INO maintenance. The remaining five patients achieved and have since sustained negative MRD status, preceding INO treatment. Fortunately, no treatment-related fatalities or treatment discontinuation due to adverse events were observed. Notably, 19 out of 27 patients (70.4%) experienced Grade 3-4 hematological toxicity, while 1 out of 24 patients (4.2%) exhibited Grade 3 alanine aminotransferase (ALT) elevation. Veno-occlusive disease (VOD) was not observed. Furthermore, two patients developed septicemia, one each from Escherichia coli and Klebsiella pneumoniae, respectively. Conclusions: Given the well tolerance and improvement in response rates, InO may be an important treatment option not only for patients with relapsed/refractory lymphoid B-cell malignancy, but also for induction, maintenance and MRD clearance treatment. Key words: inotuzumab ozogamicin, acute lymphoblastic leukemia, hematopoietic stem cell transplantation, CD22

Revumenib Monotherapy in Patients with Relapsed/Refractory KMT2Ar Acute Leukemia: Topline Efficacy and Safety Results from the Pivotal Augment-101 Phase 2 Study

Background: Most patients (pts) with histone-lysine N-methyltransferase 2A (KMT2A)-rearranged (KMT2Ar) acute leukemia, relapse after conventional chemotherapy and hematopoietic stem cell transplant (HSCT). Remission rates after relapse (complete remission [CR], 5%) and median overall survival (2.4 mo) in ≥2nd salvage therapies in adults remain low (Blood Cancer J. 2021;11[9]:162). In KMT2Ar leukemia, interaction of menin with KMT2A fusion proteins is a key driver of leukemogenesis. However, no therapies targeting the menin-KMT2A interaction have been approved. Revumenib (SNDX-5613; rev), a small-molecule inhibitor of menin-KMT2A interactions, demonstrated preliminary efficacy and safety in a phase 1 study of R/R KMT2Ar and nucleophosmin 1-mutated (NPM1m) acute leukemias. We report topline efficacy and safety for pts with R/R KMT2Ar acute leukemia treated with rev in a pivotal phase 2 study (AUGMENT-101; NCT04065399). Methods: Pts aged ≥30 days with R/R KMT2Ar acute leukemia were enrolled in cohort A (acute lymphoblastic leukemia [ALL]/mixed phenotype acute leukemia [MPAL]) and B (acute myeloid leukemia [AML]); cohort C continues to enroll pts with NPM1m and is not included in this analysis. Pts received rev (163 mg or 95 mg/m2 if body weight <40 kg) q12h with a strong cytochrome P450 3A4 inhibitor orally in 28-day cycles. Treatment continued until unacceptable toxicity or lack of at least morphological leukemia-free state (MLFS) after 4 cycles of treatment. Phase 2 primary objectives were safety and tolerability of rev and CR+CR with partial hematologic recovery (CRh) rate. Key secondary endpoints included composite CR rate (CRc, CR+CRh+CR with incomplete platelet recovery [CRp]+CR with incomplete count recovery [CRi]) and overall response rate (ORR, CRc+MLFS+partial remission). A planned interim analysis (IA) of pooled adult and pediatric pts with KMT2Ar acute leukemia was conducted. Results:As of July 24, 2023, 94 pts with R/R KMT2Ar acute leukemia received ≥1 dose of study drug and were included in the safety analysis (Table 1). Median age was 37.0 y (range, 1.3-75.0). Of the 94 pts, 23 (24.5%) were aged <18 y and 13 (13.8%) were aged ≥65 y. Seventy-eight (83%) had AML and 16 (17.0%) had ALL or MPAL. Over half of pts were female; 17.5% of pts were non-White. Pts were heavily pretreated (median 2 [range, 1-11] prior lines of therapy), with 41 pts (43.6%) having received ≥3 prior lines. Fifty-four pts (57.4%) had refractory relapse disease (unresponsive to most recent salvage treatment), and 47 pts (50%) had prior HSCT. Treatment-related adverse events (TRAEs) were reported in 81.9% of the safety population. Most common TRAEs (≥20%) were nausea (27.7%), differentiation syndrome (26.6%), and QTc prolongation (23.4%). Grade ≥3 TRAEs were observed in 51 pts (54.3%), the most common being differentiation syndrome (16.0%), febrile neutropenia (13.8%), and QTc prolongation (13.8%) (Table 2). Overall, 6.4% of pts discontinued therapy due to TRAEs; none discontinued rev due to differentiation syndrome or QTc prolongation. The pooled efficacy population for the IA (n=57) included all phase 2 pts with centrally confirmed KMT2Ar and ≥5% blasts in bone marrow at baseline who had received ≥1 dose of study drug and started treatment on or before the 38th adult AML efficacy evaluable patient. The IA was specified to occur when the 57 patients have had the opportunity to be followed for 6 months. After median follow-up of 6.1 mo, 13 pts (22.8% [95% confidence interval (CI), 12.7-35.8]) achieved CR+CRh, surpassing the predefined IA efficacy boundary for the pooled KMT2Ar population; CR+CRh rate was similar in adult and pediatric pts. Median duration of CR+CRh was 6.4 mo (95% CI, 3.4-not reached). CRc was 43.9% (95% CI, 30.7-57.6); ORR was 63.2% (95% CI, 49.3-75.6). Most pts with a CR or CRh response, and for whom measurable residual disease (MRD) status was reported, achieved MRD negativity (7/10, 70.0%); most pts with CRc and MRD reported also achieved MRD negativity (15/22, 68.2%). Fourteen of 36 responders (38.9%) proceeded to HSCT, with half resuming rev post HSCT. Conclusions: Rev demonstrated clinically meaningful results in a heavily pretreated KMT2Ar population, including high ORR and rates of MRD negativity and subsequent HSCT. At IA, this pivotal study met its primary endpoint and the KMT2Ar cohorts were stopped early for efficacy.

Superior sagittal sinus thrombosis in the course of mixed phenotype acute leukaemia treated with acute lymphoblastic leukaemia-like therapy—a case report

Mixed phenotype acute leukaemia (MPAL) is associated with worse overall survival, compared with other acute leukaemias in adults. Lack of clear treatment guidelines makes the therapy challenging. ALL-like induction and consolidation treatment followed by allo-HSCT is the preferred first-line treatment. We present a case of a 36-year-old woman diagnosed with MPAL (EGIL Myelo/B) with KMT2A rearrangement, treated with the PALG-ALL-7 (including PEG-asparaginase) protocol. On day 25 after the induction therapy initiation, numbness of limbs and dizziness were observed. Therefore, the imaging studies (CT and MRI) were performed and a diagnosis of thrombosis of superior sagittal sinus of the brain was established. Routinely performed blood coagulation tests showed prolonged APTT and PT, decreased antithrombin III activity and decreased free protein S concentration. LMWH treatment and substitutional therapy with antithrombin III were started, which resulted in a significant reduction in the thrombosis associated symptoms and improvement of the neurological status after 3 days. After induction and consolidation therapy, the patient obtained complete haematological remission and negative measurable residual disease. Six months after the diagnosis, allo-HSCT was successfully performed. During the 4 months follow-up, the patient remained MRD negative and thrombotic symptoms free. To the best of our knowledge, our communication has been the first report of such complication in an MPAL patient treated with PEG-asparaginase containing protocol in adults. We recommend increased vigilance in patients manifesting any mild neurological symptoms and early decision about the MRI study performance.

Real-World Performance of 2022 Revised World Health Organization (WHO) Criteria for Mixed Phenotype Acute Leukemia (MPAL) B/Myeloid Defined Only By Isolated MPO Expression (isoMPO)

Mixed phenotype acute leukemia (MPAL) is biologically and immunophenotypically heterogeneous, and optimal diagnostic criteria remain unclear. The two current pathologic classifications [2022 World Health Organization (WHO) 5 th Ed. and International Consensus Classification (ICC)] group MPAL by cell lineages and, when present, cytogenetic drivers. In both, myeloperoxidase (MPO) is a key determinant of myeloid lineage. However, the diagnosis of MPAL has been inconsistently applied to cases of acute leukemia expressing MPO alone to define myeloid lineage. To address this, the 2022 WHO revised prior cell lineage definitions to emphasize antigen intensity (≥50%) relative to a positive control population, attempting to standardize lineage assignment across flow cytometer settings and pathologist interpreters. Distinction between pediatric B-lymphoblastic leukemia (B-ALL) and MPAL B/Myeloid with isolated MPO is crucial for therapeutic decision-making. For example, on Children's Oncology Group (COG) regimens, patients with MPAL B/Myeloid receive an anthracycline during induction and intensified chemotherapy post-induction, whereas standard-risk B-ALL patients do not. We hypothesized that the 2022 WHO criteria applied to MPO expression in children with acute leukemia would identify leukemic subtypes (B-ALL vs. MPAL B/Myeloid with isolated MPO) with differences in clinical characteristics and/or outcome. We applied 2022 WHO criteria to flow cytometry data from a multicenter pediatric cohort of leukemias originally classified as MPAL B/Myeloid or B-ALL (Oberley AJCP 2017; Raikar Blood 2018; Oberley Leukemia 2020). Maximal antigen intensity on the leukemic population was measured in 0.5 log increments and normalized to maximal intensity of a control (neutrophil) population. MPO expression was scored as none, low (<50% intensity of mature neutrophils, the typical level in B-ALL with isolated MPO expression) or high (≥50% intensity of neutrophils, meeting 2022 WHO criteria for myeloid lineage assignment). Since the current study focused on MPAL B/Myeloid cases with isolated MPO expression, cases of MPAL T/Myeloid and of MPAL B/Myeloid with myeloid lineage assignment based on monocytic markers were excluded. Clinicopathologic data were compared with MPO expression scores by univariate and multivariate analyses. Primary endpoint was categorical difference in presenting features. Secondary endpoints were end of induction minimal residual disease (EOI MRD) ≥0.01%, event-free survival (EFS) and overall survival (OS). All analyses were two-sided; p<0.05 was the threshold for statistical significance. Among all patients at diagnosis (n=176), median age was 6.14 years (range 0.3-21), 68% were <10 years old, 59% were male, 63% were Hispanic, 76% had initial white blood cell (WBC) count <50K/µL, and 81% were CNS1. MPO was absent, low (<50%) or high (≥50%) in 48%, 29% and 23% of the cohort, respectively. Prevalence of favorable cytogenetics ( ETV6:: RUNX1 or double trisomy) was inversely proportional to MPO intensity [no MPO (50%), low MPO (27%), high MPO (17%); p<0.001). MPO expression (low or high) was more prevalent in patients >10 years of age (p<0.001). There was no difference in MPO by presenting WBC count (p=0.40). Among patients treated with ALL induction with known EOI MRD results (n=166), MPO intensity was not significantly associated with EOI MRD positivity, EFS or OS (multivariate p>0.40 for all three endpoints after accounting for presenting features and initial therapy). Our study demonstrates that 2022 WHO criteria for interpreting MPO intensity can be consistently applied to flow cytometry data from a variety of laboratories. Based on our analysis, only 44% of previous MPAL B/Myeloid cases with isolated MPO were now classified as MPAL. However, the clinical significance of this distinction remains unclear. After accounting for differences in presenting features, MPO expression was not additionally predictive of MRD positivity, EFS or OS. Further investigation is required to support the proposed threshold of 50% MPO intensity of a neutrophil control population as clinically relevant to assign myeloid lineage. Prospective standardized application of 2022 WHO cell lineage assignment criteria across centers will facilitate detailed understanding of the biological underpinnings and optimal therapeutic strategies for this heterogeneous disease.

Treatment with Blinatumomab in Combination with Venetoclax for Mixed Phenotype Acute Leukemia

Background: Mixed phenotype acute leukemia (MPAL) is a rare and heterogeneous type of acute leukemia that displays an ambiguous pattern of antigen expression to a degree that assigning a single lineage of origin is not possible due to which, understanding of the pathophysiology of the disease, diagnosis and treatment are limited. The lack of well-established optimal treatment for MPAL has paved path for requirement of a more effective and less toxic approach. Blinatumomab, a bispecific CD19-directed CD3 T-cell engager (BiTE) antibody and venetoclax, a potent, highly selective B-cell leukemia/lymphoma-2 (BCL2) inhibitor was approved for the treatment relapsed/refractory (r/r) B-acute lymphoblastic leukemia (B-ALL) and chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), respectively. Here, we present 6 patients with CD19-positive MPAL that are successfully treated with blinatumomab in combination with venetoclax and/or azacytidine in front line setting. Methods: All 6 patients met the criteria for MPAL as defined by European Group for Immunological Characterization of Acute Leukemias (EGIL) or World Health Organization (WHO 2022). Flow cytometry and polymerase chain reaction (PCR) was used to assess MRD and BCR::ABL1 or KMT2A gene, respectively. As pre-phase treatment, patients received glucocorticoid for 7 days. Blinatumomab at a dose of 9 mg/day for 1 week followed by 28 mg/day for 3 weeks combined with venetoclax at a dose of 100 mg/day for 14 to 21 days and/or azacytidine at a dose of 75 mg/m 2/day was given as induction therapy subcutaneously for 7 days. The patient with BCR::ABL1 received blinatumomab in combination with olverembatinib. Intrathecal (IT) chemotherapy with cytarabine and methotrexate was administered to central nervous system (CNS) as prophylaxis treatment. Results: Of the six patients included five were male and only one was female; five were diagnosed with B-cell/myeloid MPAL, while one with B-cell/T-cell MPAL. Abnormalities in KMT2A gene was observed in three patients while one patient had abnormality in BCR::ABL1 gene, two patients were negative for both gene abnormalities. After one cycle of blinatumomab combination treatment, all the six patients achieved complete response (CR) with full hematologic recovery. In 5 patients, MRD was <0.1% of these 3 had MRD-negative remission (<0.01%) and two patients had molecular remission. Patients were switched to chemotherapy post induction therapy, after one cycle of post-reinduction, the patients who still had the CD19-positive flow MRD or persistent molecular MRD received sequencing chemotherapy and blinatumomab. The treatment and MRD was presented in table 1. The median follow-up time was 10 months. Except 2 patients, all other patients achieved continuous MRD and molecular remission, of which two patients underwent an allogeneic hematopoietic stem cell transplant (allo-HSCT). The most frequent grade 3 or 4 adverse events (AEs) observed were anemia (6 patients), neutropenia (6 patients) and thrombocytopenia (4 patients). No AEs led to treatment interruptions and no serious AEs were reported. Conclusion: The results provide preliminary evidence of effective and safe treatment with blinatumomab and venetoclax combination as first-line therapy in MPAL resulting in the achievement of normal bone marrow function with less toxicity than using conventional chemotherapy.

A Phase I/II Study to Investigate the Addition of Venetoclax to Dasatinib and Steroids in Patients with Newly Diagnosed or Relapsed Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia (Ph+ ALL): The Venda Trial, in Progress

Background: Acute Lymphoblastic Leukemia (ALL) is a hematologic malignancy of immature lymphocytes of either B cell or T cell origin. One particularly high -risk subset is Ph+ ALL, characterized by a translocation of chromosome 9 and 22, which generates the constitutively active BCR-ABL1 fusion tyrosine kinase capable of driving proliferation and survival of leukemic cells. Currently treatment options include multi-agent chemotherapy along with an ABL-specific tyrosine kinase inhibitor (TKI), though these regimens can lead to significant toxicity, particularly in older adults. Venetoclax is a potent and selective small molecule inhibitor of the B-cell lymphoma 2 (BCL-2) anti-apoptotic protein. Strong mechanistic and preclinical data have demonstrated strong synergistic activity between dasatinib and venetoclax I xenograft models and ex vivo patient samples, and provide an impetus to further explore the combination of BCR-ABL and BCL-2 inhibition in vivo. Based on these data, we designed a clinical trial to investigate the safety and preliminary efficacy of venetoclax in combination with the second generation TKI dasatinib in Ph+ ALL. Study Design and Methods This is an open label, Phase I/II investigator initiated trial evaluating the addition of venetoclax to dasatinib and steroids (with Rituximab in CD20+ patients). Phase I is the safety and dose-finding portion of the trial combining the BCL2 inhibitor venetoclax with dasatinib and steroids during the first 28 days of induction followed by dasatinib and venetoclax for the final 48 days of induction in newly diagnosed and relapsed Ph+ ALL and mixed phenotype acute leukemia (MPAL) patients, including patients with molecular only relapse. Primary inclusion criteria include a histologically confirmed diagnosis of Ph+ ALL or MPAL. Newly diagnosed Ph+ ALL or MPAL patients may not have received leukemia-directed therapy other than for steroids or hydrea, and relapsed patients must have not had prior dasatinib exposure. Key exclusion criteria include subjects with CML in myeloid blast crisis or Ph+ AML, ECOG < 2 and patients with a history of pleural effusions. n order to determine the maximum tolerated dose (MTD) and/or recommended phase 2 dose (RP2D), a Bayesian toxicity probability interval design applied to a pre-specified targeted dose limiting toxicity rate of 30%. Three dose cohorts investigating increasing doses of venetoclax will be enrolled. Once the RP2D dose has been identified, a Phase II expansion will examine preliminary efficacy of the combination. The primary endpoint is the rate of measureable residual disease (MRD) negative remission rate as assessed by both BCR-ABL RT-PCR and next generation sequencing (NGS) after induction. Secondary endpoints include relapse-free survival (RFS) and overall survival (OS). Correlative studies include BH3 profiling (measure of apoptosis) and ex vivo screening to dasatinib and venetoclax alone and in combination. Consolidation phase with blinatumomab plus dasatinib and venetoclax is planned for the cohort expansion group. Enrollment began in September 2022 and is expected to be complete by September 2025. This trial is registered at clinicaltrials.gov (NCT04872790).

Efficacy and Safety of Avatrombopag on Thrombocytopenia after Chemotherapy in Acute Leukaemia

Background: Thrombocytopenia following chemotherapy is a common and serious complication that leads to an increased risk of bleeding and poor prognosis for patients with acute leukaemia. Current therapeutic strategies consist of platelet transfusion, recombinant human interleukin-11(rhIL-11) and recombinant human thrombopoietin (rhTPO) injection, but these strategies are not satisfactory for some patients and the treatment remains challenging. Avatrombopag is a novel thrombopoietin receptor agonist, which had been approved for thrombocytopenia in patients with chronic liver disease who are scheduled to undergo a surgery in the USA, Europe, and China, and in patients with chronic immune thrombocytopenia who were unresponsive to previous treatments in the USA and Europe. This study aims to determine the efficacy and safety of avatrombopag on thrombocytopenia after chemotherapy of acute leukaemia, and to increase the evidence for clinical use of avatrombopag. Methods: The clinical data of 24 acute leukaemia patients with grade 3/4 chemotherapy-induced thrombocytopenia (CIT) for 3-28 days were collected from February 2022 to February 2023. All patients received avatrombopag orally at a dose of 40 mg / day. Platelet (PLT) transfusion was allowed when the platelet level was less than 20×10 9/L or with bleeding events. If platelet count increased to 100 ×10 9/L or 50 ×10 9/L more than baseline, which was defined as complete response (CR), treatment of avatrombopag was stopped. Results: The median age of 24 patients with CIT was 38 (range 17‒69) years, with 14 patients diagnosed with acute myeloid leukemia (AML), 9 patients diagnosed with acute lymphoblastic leukemia (ALL), and 1 patient diagnosed with mixed phenotype acute leukemia (MPAL). Chemotherapy regiments for patients with AML included decitabine combined with venetoclax (n=5), decitabine combined with arabinoside (n=3), arsenic trioxide combined with retinoic acid (n=3), azacytidine combined with venetoclax (n=2), azacytidine combined with medium-dose arabinoside (n=1). Chemotherapy regiments for patients with ALL included CD19 specific CAR-T cells (n=3), decitabine (n=2), blinatumomab (n=2), IVP (idarubicin, vindesine, and prednisone) (n=1), azacytidine combined with venetoclax and chidamide (n=1). Chemotherapy regiment for the patient with MPAL was decitabine combined with venetoclax (n=1). At baseline, 10 patients experienced grade 3 thrombocytopenia after chemotherapy, while 14 patients experienced grade 4 thrombocytopenia after chemotherapy. The median lowest platelet count was 19×10 9/L (range 1-47×10 9/L). During the treatment period, 14 patients received platelet transfusion. The median time to reach the CR standard was 6 (range 3-26) days, and no patients stopped treatment due to side effect or drug intolerance. Compared with using avatrombopag before, the levels of platelet count were significantly increased ( P=0.000 1). The optimal platelet count of 22 patients reached the standard of CR after 7 days of drug withdrawal. Conclusion: Avatrombopag is effective on increasing platelet counts in patients with acute leukaemia after chemotherapy, with a good safety profile. It is a suitable therapeutic option for thrombocytopenia after chemotherapy.

APAL2020SC Pediatric Acute Leukemia (PedAL) Screening Trial - Developing New Therapies for Relapsed Leukemias

Background: Outcomes for children with relapsed acute myeloid leukemia (AML) and subgroups with relapsed acute lymphoblastic leukemia (ALL) remain poor, and therapeutic options are limited. There is no standard of care for relapsed disease, and data collection after relapse is lacking. In recent years, extensive molecular studies of pediatric leukemias have advanced target identification and clinical trial development. Such studies have shown that pediatric leukemias are biologically distinct from adult leukemias. The current paradigm of requiring new agent studies in adults prior to conducting pediatric trials is thus not appropriate. However, the rarity of relapsed leukemia in children makes the conduct of randomized registration trials for new agents infeasible. Recognizing that impactful progress requires international collaboration, the Leukemia & Lymphoma Society is sponsoring the Pediatric Acute Leukemia (PedAL) Initiative in North America, Australia and New Zealand. In parallel, the European Pediatric Acute Leukemia (EuPAL) Foundation has established a registry for pediatric relapsed leukemia. The principal goal of this international PedAL/EuPAL collaboration is to establish a data-driven developmental therapeutics program for children with relapsed/refractory leukemias. Trial Summary: A central component of the PedAL Initiative is the screening protocol APAL2020SC (NCT04726241), which serves as the entry point for associated therapeutic sub-trials. The primary aims of APAL2020SC are (1) to use clinical and biological characteristics to screen for eligibility for therapeutic sub-trials; and (2) to maintain a longitudinal data registry and biobank for relapsed leukemia. Eligible patients are <22 years old and have one of the following leukemias in first or greater relapse, or primary refractory: AML, myeloid leukemia of Down syndrome, T-ALL, mixed phenotype acute leukemia, and KMT2A-rearranged B-ALL. Additional eligible diagnoses include any B-ALL in second or greater relapse, and de novo or relapsed treatment-related AML. All leukemia specimens are profiled by multiparameter flow cytometry (MFC) at a central lab (Hematologics). Families have the option to submit biospecimens for banking. Patients with myeloid leukemia also have molecular testing through Foundation Medicine. Clinical data collected include demographics, cytomolecular features at diagnosis, prior treatment and post-relapse treatment. Patients are encouraged to submit follow-up bone marrow samples for central MFC. The MFC assay determines lineage and blast percent and quantifies expression of markers relevant to therapeutic sub-trials. Trial Progress: APAL2020SC opened in April 2022. As of July 25, 2023, 148 patients have enrolled and 97 have had leukemia confirmed centrally. The distribution of diagnoses is shown in Table 1. All patients had blast enumeration and target expression assessed by MFC at study entry and when follow-up samples were provided. Of the patients with myeloid leukemia (n=71), targeted DNA/RNA sequencing was successful for 69%. The distribution of AML-associated alterations is shown in Table 2. Of the patients with confirmed leukemia at enrollment, 79% submitted at least 1 follow-up sample, and 77% submitted a sample for biobanking. To date, two therapeutic trials have opened that require enrollment to the screening trial. APAL2020D/ITCC101 is a randomized phase III study comparing fludarabine-cytarabine (FLA) to FLA-venetoclax. APAL2020E/PEPN2113 is a phase 1 study of the E-selectin inhibitor uproleselan in combination with FLA. Pediatric-specific therapeutic trials for menin inhibitors and other new agents are in development. The study is collecting treatment information for children who do not enroll on a subtrial, with the goal of describing current practices and outcomes (Table 2). Conclusion: APAL2020SC will accrue patients with relapsed acute leukemias and treatment-related AML for 5 years. This protocol will promote clinical trial development by engaging industry partners and providing a single entry point to therapeutic studies with biological rationale. APAL2020SC and the EuPAL Foundation registry will generate a large, comprehensive and longitudinal dataset that will inform future trials. The biobank component will support innovative translational research to feed the pipeline of new agents.