Relapsed Acute Lymphoblastic Leukemia Research Articles

The Role of miRNAs in Childhood Acute Lymphoblastic Leukemia Relapse and the Associated Molecular Mechanisms.

Acute lymphoblastic leukemia (ALL) is the most common cancer in children worldwide. Although ALL patients' overall survival rates in wealthy countries currently surpass 80%, 15-20% of patients still experience relapse. The underlying mechanisms of relapse are still not fully understood, and little progress has been made in treating refractory or relapsed disease. Disease relapse and treatment failure are common causes of leukemia-related death. In ALL relapse, several gene signatures have been identified, but it is also important to study miRNAs involved in ALL relapse in an effort to avoid relapse and to achieve better survival rates since miRNAs regulate target genes that participate in signaling pathways involved in relapse, such as those related to drug resistance, survival signals, and antiapoptotic mechanisms. Several miRNAs, such as miR-24, miR-27a, miR-99/100, miR-124, miR-1225b, miR-128b, miR-142-3p, miR-155 and miR-335-3p, are valuable biomarkers for prognosis and treatment response in ALL patients. Thus, this review aimed to analyze the primary miRNAs involved in pediatric ALL relapse and explore the underlying molecular mechanisms in an effort to identify miRNAs that may be potential candidates for anti-ALL therapy soon.

Histone deacetylase inhibition sensitizes p53-deficient B-cell precursor acute lymphoblastic leukemia to chemotherapy.

In pediatric acute lymphoblastic leukemia (ALL), mutations/deletions affecting the TP53 gene are rare at diagnosis. However, at relapse about 12% of patients show TP53 aberrations, which are predictive of a very poor outcome. Since p53-mediated apoptosis is an endpoint for many cytotoxic drugs, loss of p53 function frequently leads to therapy failure. In this study we show that CRISPR/Cas9-induced loss of TP53 drives resistance to a large majority of drugs used to treat relapsed ALL, including novel agents such as inotuzumab ozogamicin. Using a high-throughput drug screen, we identified the histone deacetylase inhibitor romidepsin as a potent sensitizer of drug responsiveness, improving sensitivity to all chemotherapies tested. In addition, romidepsin improved the response to cytarabine in TP53-deleted ALL cells in vivo. Together, these results indicate that the histone deacetylase inhibitor romidepsin can improve the efficacy of salvage therapies for relapsed TP53-mutated leukemia. Since romidepsin has been approved for clinical use in some adult malignancies, these findings may be rapidly translated to clinical practice.

Results from the Phase 1 Portion of a Trial of Oral Ixazomib Combined with Chemotherapy in Relapsed/Refractory Acute Lymphoblastic Leukemia or Lymphoma in Children, Adolescents and Young Adults: A Report from the Therapeutic Advances in Childhood Leukemia and Lymphoma (TACL) Consortium

ACKNOWLEDGEMENT Proteasome inhibitors potentiate anti-tumor effects of standard cytotoxic chemotherapy in childhood leukemia. Ixazomib is an oral proteasome inhibitor that has a shorter proteasome dissociation half-life than bortezomib, which leads to a higher tumor-to-blood ratio inhibition. We performed a phase 1 trial to determine the dose limiting toxicities (DLT), Recommended Phase 2 Dose (RP2D) of ixazomib in pediatric patients with relapsed/refractory acute lymphoblastic leukemia (ALL) or lymphoma (LL). Patients ≤ 21 years of age with relapsed or refractory ALL (with ≥ 5% detectable disease in the marrow) or LL were eligible. Ixazomib was combined with 28-day blocks of well-established, relapsed ALL backbone chemotherapy. Block 1 contained vincristine (1.5 mg/m 2/dose IV Days 1, 8, 15, 22), dexamethasone (5 mg/m 2/dose IV or oral twice daily Days 1-14), PEG-asparaginase (2500 IU/m 2/dose IV Days 2, 15) and daunorubicin (60 mg/m 2/dose IV Day 1) (VXLD). An optional Block 2 contained vincristine (1.5 mg/m 2/dose IV Day 1), dexamethasone (3 mg/m 2/dose oral twice daily Days 1-5), methotrexate (1000 mg/m 2/dose IV over 36 hours Day 8), PEG-asparaginase (2500 IU/m 2/dose IV Day 9), cyclophosphamide (440 mg/m 2/dose IV Days 15-19) and etoposide (100 mg/m 2/dose IV Days 15-19). An additional optional Maintenance Block contained vincristine (1.5 mg/m 2/dose IV Day 1), prednisone (20 mg/m 2/dose oral twice daily Days 1-5), mercaptopurine (75 mg/m 2/dose oral daily) and methotrexate (20 mg/m 2/dose oral weekly). Intrathecal therapy was given throughout with agents and dosing based on the patient's CNS disease status upon study entry. Ixazomib was given orally and tested at two dose levels (DL) (DL1: 1.6 mg/m 2/dose; DL2: 2 mg/m 2/dose) using a 3+3 design and was given during Block 1 on Days 1, 4, 8 and 11; during Block 2 on Days 1, 4, 8, 15 and 18 and during Maintenance on Days 1, 8 and 15. DLTs during Block 1 only were utilized to make DL escalation decisions and determine the RP2D. Patients without Down Syndrome (DS) entered Cohort A, used to determine the P2RD. Patients with DS were eligible for a 1 DL lagging descriptive-only Cohort B. Ten patients were treated; nine in Cohort A (n = 3 at DL1 and n = 6 at DL2) and one in Cohort B (DL1). Median age (range) at study entry was 10.5 years (5 - 20 years). Nine patients had B-ALL and one had T-ALL. Most were heavily pretreated with a median (range) of 3.4 (1 - 7) previous remission attempts with six having had prior immunotherapy and three patients having had at least one prior hematopoietic stem cell transplant. After Block 1, two patients received Block 2 and one received Maintenance. In Block 1 of Cohort A, non-hematological Grade 3/4 adverse events (AE) possibly, probably or definitely related to ixazomib or the backbone chemotherapy were limited and included neutropenic fever (n = 7), increased AST (n = 3), increased ALT (n = 2) and hypokalemia (n = 2). Two septic events occurred (n = 1 in Cohort A (Grade 3) and n = 1 in Cohort B (Grade 4)). Block 2 and Maintenance AEs were not significantly different than those seen in Block 1. No deaths or DLTs occurred. Response assessment showed that at DL1 two of three patients had a Complete Remission (CR) both of whom were Minimal Residual Disease (MRD) negative (-) and at DL2 three of six patients had a CR, two of whom were MRD- and two patients had a CR with incomplete count recovery (CRi). The overall response rate (CR + CRi) was 78% (7 of 9 patients). With a minimum of 20 months of follow-up six of nine patients in Cohort A and the single patient in Cohort B are still alive. All three deceased patients died of disease progression. Ixazomib can be combined with standard chemotherapy with an acceptable safety profile and an encouraging early efficacy signal in pediatric relapsed ALL including those with DS. The RP2D of Ixazomib combined with chemotherapy is 2 mg/m 2/dose, which is being used in the ongoing phase 2/expansion cohort of the study. We acknowledge the TACL Consortium's scientific contribution to and participation in this study, including participating member institutions, investigators, research teams, and the TACL Operations Center. Takeda Pharmaceuticals Company provided the investigative drug and funding in support of this trial.

Outcomes and Prognostic Factors of Second Allogeneic Hematopoietic Cell Transplantation in Patients with Acute Lymphoblastic Leukemia: A Study from the Adult Acute Lymphoblastic Leukemia Working Group of the Japanese Society for Transplantation and Cellular Therapy

Background Allogeneic hematopoietic cell transplantation (allo-HCT) is a curative treatment option frequently used in patients with acute lymphoblastic leukemia (ALL). However, relapse after allo-HCT remains the main concern because it is associated with poor outcomes, with a long-term survival rate < 10 %. There is no standard treatment for patients with ALL who relapsed after allo-HCT. Second allo-HCT (allo-HCT2) is a curative treatment option for patients with ALL who relapsed after the first allo-HCT (allo-HCT1). However, data on allo-HCT2 in patients with ALL are limited, and the indications and outcomes of allo-HCT2 are unclear. Therefore, this study aimed to investigate the outcomes and prognostic factors of patients who underwent allo-HCT2 after ALL relapse. Methods This study included 425 adult patients with ALL who underwent allo-HCT2 after relapse between January 2001 and December 2020. The primary endpoint was 2-year overall survival (OS), which was evaluated using the log-rank test. Prognostic factors for the primary endpoint were evaluated using the multivariable Cox proportional hazards model. The variables considered in the Cox proportional hazards model are listed in the Table. The impacts of the candidate factors are shown as hazard ratios (HRs) and 95% confidence intervals (CIs). Additionally, we performed an analysis stratified by disease and disease status because Philadelphia chromosome (Ph)-positive B-ALL could affect the treatment and disease status at allo-HCT2 and the outcome. Results The median age at allo-HCT2 was 36 years (interquartile range; 27-48 years) and 220 patients (52%) were male. According to the Eastern Cooperative Oncology Group, 94 patients (22%) had a performance status of > 2. There were 235 patients (55%) with Ph-negative B-ALL, 122 patients (29%) with Ph-positive B-ALL, and 68 patients (16%) with T-ALL. Regarding disease status at allo-HCT2, 217 patients (51%) had any complete response (CR). One hundred forty-eight patients (35%) received myeloablative conditioning regimen. Ninety patients (21%) received related bone marrow (BM) or peripheral blood (PB) transplantation, 137 patients (32%) received unrelated BM or PB transplantation, and 198 patients (47%) received unrelated cord blood (CB) transplantation. The median observation time of survivor after allo-HCT2 was 22.3 (interquartile range; 6.3-82.5) months and 2-year OS was 28.0% (95% CI, 23.7-32.4). After stratified disease and disease status, the 2-year OS was 56.5% (95% CI, 44.6-66.8), 31.7% (95% CI, 24.0-39.7), 21.5% (95% CI, 10.6-34.9), and 13.1% (95% CI, 8.4-18.8) in any CR (Ph-positive B-ALL), any CR (other), active disease (Ph-positive B-ALL), and active disease (other), respectively ( P < 0.001) (Figure). In multivariable analysis, Ph-positive B-ALL (HR, 0.48; 95% CI, 0.36-0.65; P < 0.001), tacrolimus-based GVHD prophylaxis at allo-HCT2 (HR, 0.72; 95% CI, 0.54-0.95; P = 0.022) were identified as significantly positive prognostic factors for 2-year OS, while allo-HCT1 to allo-HCT2 < 12 months (HR, 1.38; 95% CI, 1.02-1.88; P = 0.038), relapse within 12 months after allo-HCT1 (HR, 1.37; 95% CI, 1.01-1.85; P = 0.043), ECOG PS > 2 (HR, 1.89; 95% CI, 1.44-2.49; P < 0.001), active disease at allo-HCT2 (HR, 1.88; 95% CI, 1.46-2.42; P < 0.001), unrelated BM or PB transplantation at allo-HCT2 (HR, 1.78; 95% CI, 1.22-2.59; P = 0.003), and CB transplantation at allo-HCT2 (HR, 1.54; 95% CI, 1.09-2.18; P = 0.013) were identified as significantly negative prognostic factors for 2-year OS. Conclusion In this study, we demonstrate that the 2-year OS was 28.0% in patients with ALL who underwent allo-HCT2 and identified the prognostic factors that may guide patients to benefit from allo-HCT2.

Transcriptomic without Clinical Response to Menin Inhibition As a Mechanism of Upfront Resistance in Samples from Mutliply Relapsed Patients with KMT2A-Rearranged Leukemia

Inhibitors of the Menin-KMT2A interaction are emerging as promising agents for the treatment of KMT2A-rearranged ( KMT2A-r) acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Menin is required for the recruitment of the KMT2A-fusion to a subset of its target genes. Early phase clinical trials have shown highly encouraging results in patients with relapsed and refractory leukemias with KMT2A rearrangements and NPM1 mutations. In a recently reported early phase clinical trial evaluating the Menin inhibitor revumenib, about 50% of patients failed to show a clinical response despite robust downregulation of known Menin:KMT2A target genes, suggesting on target activity of the drug. This was the most common pattern of upfront resistance. We sought to understand upfront resistance (in contrast to the reported induced resistance via MEN1 mutations) in patient derived xenograft models. To this end, we evaluated the efficacy of Menin-inhibition in KMT2A-r leukemias with high-risk features: high-risk KMT2A fusion partners in AML ( MLLT10, MLLT4), infant ALL, and serial samples from patients with multiply relapsed ALL. We found that AML samples with high-risk fusion partners banked at initial diagnosis were sensitive to Menin-inhibition in xenografts. In contrast, three highly pretreated samples from patients with KMT2A-AFF1 ALL showed only a slight, or no decrease in latentcy in the Menin-inhibitor arm. Interestingly, Menin inhibition showed excellent in vivo efficacy against leukemia samples obtained from the same three patients earlier in their disease course. Therefore, prior chemotherapy (+/- immunotherapy) selects for Menin-inhibitor resistant cells without prior exposure to Menin inhibitor. Transcriptomic analysis (RNA-Seq) documents sustained on-target efficacy of the Menin inhibitor on a transcriptional level in resistant cells. None of the samples contained a MEN1 mutation at any time point. Targeted panel sequencing at initial diagnosis and relapse documented clonal evolution and the emergence of multiple co-mutations (particularly RAS pathway mutations and TP53 mutations), however, all co-mutations tested failed to induce resistance as a single alteration. It is possible that the cooperation of multiple emerging mutations (rather than a single mutation) is sufficient to drive AML in a KMT2A-fusion independent manner, thus mediating Menin resistance. A transcriptomic response (i.e. downregulation of KMT2A-fusion target genes) without a clinical response was the most common pattern of upfront resistance in the recently reported phase I/II clinical trial of the Menin inhibitor revumenib. We conclude that it will be critical to use Menin-inhibitors upfront or in early lines of therapy before substantial clonal evolution has occurred.

The Relapse Mechanisms and Genomic Landscape Differ in KMT2A-r Pediatric Leukemia in Relation to Relapse Time

The genomic landscape and mechanisms driving relapse in KMT2A-rearranged ( KMT2A-r) infant and childhood acute lymphoblastic (ALL) and acute myeloid leukemia (AML) are not completely understood. We therefore studied 36 KMT2A-r ALL (n=19) and AML (n=17) patients of which 25 relapsed and 11 remained in remission. Twenty diagnose-relapse-germline trios and 5 multiple relapse samples were analyzed by whole genome (WGS) and whole exome sequencing (WES) and 30 patients longitudinally by using patient-specific mutations identified by WGS/WES, including the KMT2A-r (average coverage 3300X). The mutational burden increased from diagnosis to relapse and relapse evolved through branching evolution. Relapse was seeded by multiple diagnostic clones in 56%, by a single sweeping clone detected at diagnosis in 22%, and by a single sweeping clone not detected at diagnosis in 22%. Notably, the evolutionary patterns correlated to relapse time, where multiple diagnostic clones seeding relapse were connected to an earlier relapse with all very early relapse ALL (3/3, relapse <9 months from diagnosis) and half of the early AML relapse showing this pattern (2/4, relapse <1 year in complete remission, CR1). By contrast, later relapse was connected to a sweeping clone at relapse with 67% of early relapse ALL (>9 months from diagnosis) and 40% of late relapse AML (>1 year in CR1) showing this pattern. Pathway analysis showed that cell cycle genes, glucocorticoid signalling, purine metabolism, mismatch repair, and B-cell differentiation, were enriched in early relapse ALL (83%, 5/6) and included TP53, CREBBP, NT5C2 PMS2, PRPS2, NR3C1, IKZF1, with none of the very early relapse infant ALL harboring such alterations (n=4). Further, TP53 and IKZF1alterationsco-occurred (n=4/4). These results were validated in public data sets of 98 KMT2A-r ALL infants (n=84) and children (n=14) at diagnosis and relapse (n=24) and showed that 50% of early relapse ALL, and none of the 8 very early relapse ALL, had such alterations. Ultra-deep sequencing did not detect the CREBBP, NT5C2, PRPS2or TP53 mutations at diagnosis and manual inspection of the WGS reads failed to detect the PMS2 and NR3C1 deletions. In AML, TP53 and CCND3 alterations were maintained, and gain of WT1 was seen in late relapse AML. Signalling mutations were the most common type of mutations at diagnosis (64%) and relapse (56%) and the frequency was similar in patients that remained in remission and in those that relapsed (55% versus 60%). One infant ALL and four AML patients had multiple relapses, allowing us to study how the genetic landscape evolved across consecutive relapses. This showed a stepwise replacement of clones during treatment in agreement with a fitter clone that evolves under chemotherapeutic selective pressure. Longitudinal analysis allowed sensitive detection of residual leukemia cells and showed that the relapse clone could be detected at diagnosis in 64% of patients. Further, infants with >10% of molecularly detectable leukemia cells after induction therapy, had a high risk of a very early relapse. Ultra-deep sequencing allowed detection of the relapse clone up to 4 months before relapse. In 11 of the 30 patients (3 remission and 8 relapse), low-frequency KMT2A-fusion positive leukemic cells were found at remission outside of the MRD time points. Our longitudinal data also provided unique insights into clonal response to treatment by showing that 1) a change in therapy can favour the eradication of one clone and expansion of another, 2) a clone that initially was the most sensitive clone to therapy, was the one that eventually caused relapse, and 3), a diagnostic clone can be undetectable for a long time before expanding to cause relapse, suggesting that molecular monitoring with personal mutations is a powerful tool to follow response to therapy. These results provide new biological insights into the relapse mechanisms in KMT2A-r leukemia. The data shows different clonal evolution patters depending on when in time the patient relapsed, with very early relapse ALL being seeded by multiple diagnostic subclones and a paucity of acquired genetic alterations at relapse. By contrast, early relapse ALL was characterized by a single diagnostic clone seeding relapse by a clonal sweep along with acquired mutations in chemoresistance-associated genes. To validate and extend these findings, we are currently analyzing 11 additional infant relapse samples with WGS.

The Different Impacts of an MRD-Guided Protocol on Relapse of Childhood Acute Lymphoblastic Leukemia: The Report of Taiwan Pediatric Oncology Group (TPOG)-ALL-2013

Taiwan Pediatric Oncology Group (TPOG)-ALL-2013 protocol (TPOG-2013), modifying from St. Jude Total Therapy XV Study and Total Therapy XVI Study, was launched since January 2013. This is the first nationwide minimal residual disease (MRD)-directed protocol for treatment of childhood acute lymphoblastic leukemia (ALL) in Taiwan. According to TPOG-2013, two MRD measurements were scheduled on days 15-19 of induction (MRD1 time point, TP1) and days 35-42, end of induction (MRD2 time point, TP2) to make the definitive risk stratification to guide subsequent therapy. As of April 30, 2023, 814 newly diagnosed ALLs treated with TPOG-2013 and followed up ≥3 years were enrolled in the study. The outcomes were compared with those of TPOG-ALL-2002 protocol (TPOG-2002) (N=1350, between January 2002 and December 2012), which did not integrate the MRD monitoring. The 5-year event-free survival and overall survival were significantly improved from 76% (95% CI, 74-78) and 81% (80-84) of TPOG-2002 to 86% (83-88) and 89% (87-92) of TPOG-2013, respectively ( P< 0.0001). For further analysis of TPOG-2013, 585 (72%) patients with exact adherence (EA) to both TPs were assigned as MRD EA group; 225 patients who were non-adherence (NA) to either one of TPs as MRD NA group; and four patients were excluded for the comparative outcome analysis. For B-cell precursor (BCP) ALL, the 5-year cumulative incidence of relapse (CIR) significantly decreased from TPOG-2002 (N=1194) to TPOG-2013 MRD EA (N=527) ( P <0.0001). However, there was no significant improvement of CIR between TPOG-2002 and MRD NA (N=202) ( P= 0.21) (Figure 1). In MRD EA of BCP-ALL, compared with TPOG-2002, patients with ETV6::RUNX1 or BCR::ABL1 appeared to have significantly lower CIR. Patients without the common genetic subtypes , denoted as “negative” group, also had significant inferior CIR. And the trend of CIR decrease did not attain significant difference in high hyperdiploidy. In contrast, patients with T CF3::PBX1 or infant with KMT2A-rearrangement did not show CIR improvement (Table 1). In T-ALL, compared with TPOG-2002 (N=156), there was a significant decrease of CIR in TPOG-2013 MRD EA (N=58)( P= 0.01)(Table 1), but not in MRD NA (N=23)( P= 0.86). There was a longer duration to relapse in MRD EA of BCP-ALL. However, a delay of relapse was only demonstrated in patients with BCR::ABL1, which could be addressed by the introduction of MRD-monitoring and TKI inhibitor in TPOG-2013 (Table 1). Further, in term of early relapse before 1.5 year of remission, there was no significant difference in MRD EA of BCP-ALL, compared with TPOG-2002. In conclusion, this study demonstrated diffident impacts on relapse according to genetic subtypes and MRD adherence. In the negative group of BCP-ALL without the discovery of novel genetic alternations, the relapse could be much decreased with the MRD-directed treatment protocol.

High Dimensional Clustering and Identification of Immune Cell Hybrid Populations in B-ALL across the Disease Continuum

Introduction: Nearly half of adults with acute lymphoblastic leukemia (ALL) will experience relapse of their disease, and those with relapsed ALL carry a worse prognosis than those who remain in remission. The influence of the tumor immune microenvironment (TME) on relapse and survival outcomes in ALL is not well understood. Mass cytometry (CyTOF) enables immune profiling based on single cell protein expression and can identify phenotypic diversity of cells in the TME that cannot reliably be detected by standard flow cytometry. Recently, T-cell/monocyte hybrid cells have been discovered in patients with uveal melanoma and latent tuberculosis infections. However, cells expressing CD19, a surface antigen expressed on B-ALL cells, and markers of other cells in the TME including T cells and tumor-associated macrophages (TAMs), have not been described in ALL or other hematologic malignancies. The presence of CD3/CD163 hybrid cells in the TME may have predictive and prognostic implications for adults with ALL, as TAMs play a role in suppressing antitumor immunity which can lead to T-cell exhaustion. In this study, we identify the presence of multilineage hybrid cells in peripheral blood (PB) and bone marrow (BM) samples of patients with B-ALL alongside accompanying evolution of the TME at each disease stage. Methods: PB (N=16) and BM aspirate (N=16) isolates were collected from patients with B-ALL at diagnosis, relapse, or remission, as well as from healthy donors (HDs, N=7) for comparison of cellular profiles. A 28-marker CYTOF panel was designed to evaluate cell surface and intracellular markers of interest in the myeloid compartment. Antibodies were purchased pre-conjugated or conjugated in house based on manufacturer guidelines (Standard BioTools). Samples were barcoded with palladium isotopes prior to staining to reduce the impact of batch effect, and were then analyzed on a first generation CyTOF system (Standard BioTools). Following background attenuation and singlet gating in FlowJo (BD), the CATALYST R package enabled deconvolution and visualization of single cell data, including dimensional reduction techniques (tSNE) and clustering of all cell populations. An iterative approach was taken to determine a stable configuration of clusters across sample populations to protect from over-fragmentation of data, further informed by K-means clustering using the elbow method. Heatmaps were then generated based on median scaled expression of markers contained in each cluster. Results: The CyTOF panel identified several different myeloid cell populations in newly diagnosed, relapsed, and remission samples in both PB and BM compared to HDs. Most interestingly, quantifiable levels of a cluster of cells co-expressing CD19, CD3 and CD163 as well as a second cluster of cells expressing CD19 and CD163 were detected in newly diagnosed and relapsed patients, but not in HDs. A single patient with the largest proportion of these cell populations in their PB at the time of relapse presented with an aggressive leukemia variant and relapsed multiple times prior to succumbing to illness. On investigation of BM aspirates, the triple positive hybrid population was found in a similar distribution amongst the newly diagnosed and relapsed patients, as well as affecting one patient who achieved remission. This patient also had a highly aggressive leukemia that was refractory to chemotherapy and immunotherapy, and only achieved this remission following CAR-T cell therapy. She subsequently underwent stem cell transplant and is in remission. Conclusions: Our findings add to the literature highlighting the utility of high parameter single cell capture techniques in detecting rare cell populations in the leukemic TME. Further, we identified two unique hybrid cell populations that are reliably detected across different disease stages in patients with B-ALL. Importantly, these populations persisted following stringent gating protocols to rule out doublets and debris. Although our sample size was too small to demonstrate a prognostic impact of these hybrid cell populations in patients with B-ALL, the identification of these populations alone is a significant finding. Further investigation and patient sample accrual are warranted to better understand the role of these cell types in tumor biology, which may pave the way towards new prognostic models that can leverage well-established immune monitoring techniques.

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.

In Vitro Efficacy of Anti-HER2 CAR T-Cells in HER2 + BCP-ALL

Introduction: Around 30% of adults and 15% of children with B cell precursor acute lymphoblastic leukemia (BCP-ALL) relapse after a first line of treatment. The prognosis of these patients remains poor. Recent advances have involved targeted therapies with monoclonal antibodies and chimeric antigen receptor (CAR) T-lymphocytes (anti-CD19 CAR T-cells), which have produced very encouraging results in the high risk BCP-ALL setting(Maude et al. 2018). Nevertheless, half of these patients relapse after such therapies. In a third of cases, the disease no longer expresses the antigen previously targeted. New targets are therefore needed. HER2 is expressed in above one third of adult BCP-ALL (Chevallier et al. 2004) and 10% of childhood BCP-ALL (Camuset et al. 2021). HER2 expression is associated with chemoresistance and poor prognosis (Chevallier et al. 2004) (Camuset et al. 2021). The anti-HER2 antibody trastuzumab was prospectively tested in adult patients with HER2+ BCP-ALL, but yielded disappointing results (Chevallier et al. 2012). Anti-HER2 CAR T-cells could be an interesting alternative. Indeed, they have shown encouraging preclinical efficacy in solid tumors expressing HER2/neu (Budi et al. 2022). The present work was designed to evaluate, in vitro, the sensitivity of HER2+ BCP-ALL to anti-HER2 CAR engineered Epstein Barr virus (EBV) specific T-cells. Methods: DMSO-frozen cell-samples from 6 HER2+ BCP-ALL patients were available for this study. Patient characteristics are shown in Table 1. Blast cells from patient samples were preferred to cell lines in order to be more representative of BCP-ALL biology. level of HER2 expression on BCP-ALL samples was determined by flow cytometry and compared to the HER2 expressing breast-cancer cell line BT474. Anti-EBV cytotoxic T lymphocytes (CTLs), armed with a trastuzumab-based scFv-CH2-CH3-IgG2A-FcεRIγ chimeric receptor as previously described (Clémenceau et al. 2015) were used for long-term cytoxicity assays. For 4 samples, non-transduced anti-EBV CTLs were used as controls. Cytotoxic activity was assessed at a 3-to-1 effector-to-target ratio, in a flow cytometry assay. Cells were harvested at H0, H4 and H24 and stained with a viability stain (VS780). Further staining with anti-CD22 or anti-CD24 (depending on the BCP-ALL immunophenotype) and anti-CD3 antibodies allowed to characterize blast cells and CAR T-cells respectively. The study was approved by the local review board and two alive patients provided informed consent. Results: The level of HER2 expression by the 6 HER2+ BCP-ALL samples was variable with a median relative fluorescence intensity ratio (RFI) of 9 (range 1.8 to 16). These levels of expression were lower than those of the BT474 cell line (RFI= 79). No BCP-ALL lysis was observed when cells were incubated with trastuzumab alone (not shown). When co-cultured with non-transduced anti-EBV CTLs (CAR negative) (n=4), a decrease of residual viable BCP-ALL cells was observed at variable levels (Figure 1A). The lysis observed at 24h was possibly due to allogeneic recognition since anti-EBV CTLs were not autologous to the leukemias tested. Conclusion: This study first reveals that, although CTLs with TCRs restricted to EBV antigens and therefore intrinsically low allo-specificity were used, CAR-independent lysis was observed in 24 hours co-culture with BCP-ALL cells. These results underline the need for cautious interpretation of cytotoxicity test results in an allogeneic setting. Secondly, these preliminary data suggest that an anti-HER2 CAR T-cell approach could be promising for BCP-ALL even with weak antigen expression. Anti-EBV CTLs have already been used as a platform for CAR-engineered T-cells (Rossig et al. 2017). Should the cytotoxic activity of allogeneic EBV-CTL be proven to be specifically directed against BCP-ALL, the synergy between TCR and anti-HER2-CAR might be beneficial, and adoptive transfer of anti-HER2 CAR EBV CTLs could be a promising therapeutic option for patients with HER2+ BCP-ALL. * This research is funded by the non-profit organization Etoile de Martin/SFCE.

4SCAR2.0 therapy for the management of post-transplantation relapse of B-cell acute lymphoblastic leukemia

IntroductionAllogeneic hematopoietic stem cell transplantation (allo-HCT) is a standard treatment for relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL). However, about 30-40% of patients still relapse after HCT. Chimeric antigen receptor-modified T-cell (CAR-T) therapy has been proven effective in the treatment of relapsed or refractory B-ALL.Patients and methodsWe report a cohort of 30 B-ALL patients, who relapsed after HCT and were enrolled in the 4SCAR2.0 study, receiving CD19 CAR-Ts alone (20 patients), or two types of CAR-Ts targeting CD19, CD22, CD38 or CD123 antigens (10 patients), depending on the tumor antigen expression profile. These patients had extramedullary (EM) relapse or bone marrow (BM) relapse, or both. Based on the GVHD history, donor chimerism, and the available T-cell source, 25 patients received allogeneic donor CAR-Ts, and 5 patients received autologous CAR-T treatment. ResultsAll 20 patients receiving a single CD19 CAR-T infusion achieved a minimal residual disease (MRD) remission within 60 days. The remaining 10 patients, due to low CD19 antigen expression profile, received 2 CAR-T products given on the same day, and 9 of 10 achieved complete remission (CR) and one had disease progression within 60 days. After CAR-T infusion, no cytokine release syndrome (CRS) was observed in 14 patients, and 16 patients experienced grade 1 CRS, and there was no neurotoxicity. Seventeen of the 30 patients who achieved remission (57%) remained in continuous remission following CAR-T treatment with a median follow-up period of 2 years and a median duration of remission of 12 months (range: 2.8 months - 67 months). Twelve out of 29 patients (41%) who achieved remission, subsequently relapsed at a median of 6.3 months (range: 2.8 months - 22.3 months) after CAR-T treatment. In summary, 29 patients (97%) achieved MRD negative remission within 60 days of therapy with a single or double CAR-T infusion, and seven patients remained in durable remission (7/30, 23%) after more than 2 years of follow-up. DiscussionThe tumor antigen profile-guided precision 4SCAR2.0 regimen for the treatment of r/r B-ALL after allo-HCT was highly effective with low toxicity. This approach warrants extended follow-up and further studies. Clinical trial registrationClinicalTrials.gov, identifier NCT03125577.

PIWIL1 gene polymorphism and pediatric acute lymphoblastic leukemia relapse susceptibility among Chinese children: a five-center case-control study.

PIWIL1 polymorphisms' role in pediatric acute lymphoblastic leukemia (ALL) relapse susceptibility remains undiscovered. A case-control designed and multiple logistic regression model was performed to evaluate the overall risk of pediatric ALL and five single-nucleotide polymorphisms (SNPs) of PIWIL1 gene (rs35997018 C>T, rs1106042 A>G, rs7957349 C>G, rs10773771 C>T, and rs10848087 A>G) in 785 cases and 1,323 controls, which were genotyped by TaqMan assay. The odds ratio (OR) and its 95% confidence interval (CI) were used to estimate the relationship. Stratified analysis was used to investigate the correlation of rs1106042 and rs10773771 genotypes and pediatric ALL relapse susceptibility in terms of age, sex, number of white blood cells (WBC), immunophenotyping, gene fusion type, karyotype, primitive/naïve lymphocytes, and minimal residual disease (MRD) in bone marrow. Finally, the haplotype analysis was performed to appraise the relationship between inferred haplotypes of PIWIL1 and pediatric ALL risk. Among the five analyzed SNPs, rs1106042 A>G was related to increased ALL risk, and rs10773771 C>T was related to decreased ALL risk. Compared to the GG genotype, the rs1106042 GA/AA had a deleterious effect on children of age <120 months, who were female and male, had high or average number of WBC, pro-B ALL, pre-B ALL, T-ALL, low- and middle-risk ALL, E2A-PBX fusion gene, non-gene fusion, abnormal diploid, high hyperdiploid, hypodiploid, and normal diploid. Moreover, rs1106042 A>G harmfully affected primitive/naïve lymphocytes and MRD on days 15-19, day 33, and week 12. On the contrary, rs10773771 TC/CC exhibited a protective effect on ALL children with the TEL-AML fusion gene. Haplotype analysis demonstrated that haplotypes CAGT, TACC, TACT, and TAGT were significantly associated with increased pediatric ALL relapse susceptibility. PIWIL1 rs1106042 A>G was related to increased ALL risk, and rs10773771 C>T was linked to decreased ALL risk in eastern Chinese children. Rs1106042 GA/AA may predict poor prognosis.

Exploring the Efficacy and Feasibility of Outpatient Blinatumomab Short Cycles in Pediatric Patients with Relapsed/Refractory B-ALL in LMIC: Preliminary Results

CONCLUSIONS In low- and middle-income countries (LMIC) like Mexico, the treatment of patients with refractory or relapsed acute lymphoblastic leukemia (r/r ALL) represents a significant challenge due to limited access to immunotherapy and hematopoietic stem cell transplantation (HSCT). As a result, the one-year survival rate is reported to be less than 20%. The use of intensive chemotherapy has not improved survival in this group due to its high toxicity. Blinatumomab uses the patient's own cytotoxic T-cells to induce lysis of the leukemia cells expressing CD19 and has been established as a bridge therapy for transplant in patients with r/r B-ALL. The usual pattern of administration is a dose scaled up to complete a total of 28 days of infusion. According to various studies, it is considered appropriate to use repeated cycles of this antibody to achieve the desired response. However, there are also reports of patients achieving complete responses within the first 15 days of the cycle. The high costs of Blinatumomab's administration present a significant barrier to its use in LMIC. As a consequence, the application of prolonged or multiple cycles of the drug becomes unaffordable for a substantial portion of the global population. Demonstrate the safety and efficacy of utilizing short cycles of Blinatumomab (21 days) as a bridge therapy to HSCT in pediatric patients with r/r ALL to explore the potential cost-reduction benefits and increased access to this therapy in resource-limited settings. A pilot clinical trial was conducted. Pediatric patients (&amp;lt;16 y) diagnosed with r/r B- ALL between the years 2020-2022 were included. The usual Blinatumomab dosing regimen was adopted, but the total duration of the cycle was reduced. Continuous infusion was initiated at a dose of 5 mcg/m2/day for the first 7 days, followed by an increase to 15 mcg/m2/day for 14 days (21-day total treatment duration). To mitigate cytokine release syndrome (CRS) a single dose of dexamethasone was administered at the start of the infusion and after the dose escalation. The entire regimen was administered on an outpatient basis, with an infusion pump at home. Caregivers were instructed on the operation of the pump and detection of any signs of toxicity, with 24/7 contact with the medical team and the option to hospitalize if necessary. A total of 7 patients were included, and all of them received Blinatumomab in a single 21-day cycle. The median age was 5 years (15 mo- 13 y). The majority of patients were stratified as high-risk at the time of diagnosis (85.7%). Among the patients, 4 had relapsed ALL, while 3 had refractory disease. The median time from the initial diagnosis to the use of Blinatumomab was 16 months (ranging 7-29 mo), and the median number of treatment lines before Blinatumomab administration was 3 (ranging 2-4). The highest level of minimal residual disease (MRD) detected before the Blinatumomab treatment was 4.2% (by flow cytometry). Remarkably, all patients (100%, n=7) achieved a complete response, with MRD being negative for flow cytometry after the 21-day cycle of Blinatumomab. In 5 out of 7 patients, the administration of the drug was completely ambulatory. Only 2 patients experienced grade I CRS which was successfully managed with steroids. No adverse effects greater than grade 2 were reported, and no patient required support with transfusion therapy during or after the infusion. There were no reports of profound neutropenia, and no treatment-related deaths occurred. HSCT was conducted in all patients to consolidate the response, with 6 patients undergoing haploidentical and 1 patient undergoing identical allogeneic HSCT. At present, 5 out of 7 patients are alive and in complete remission. One patient died on day +51 post-HSCT due to pulmonary thromboembolism, and the second patient experienced relapse on day +395 post-HSCT and subsequently died on day +640 due to disease progression. The median overall survival at 3 years was 66.7%, with a median follow-up period of 21 months (4 -30mo). An alternative outpatient, low-toxicity and cost-effective treatment approach was implemented. The findings from this study could shed light on a promising strategy to improve the outcomes for patients with ALL patients with limited therapeutic options, particularly in the context of resource-constrained settings.

Association between High Antimetabolite Dose Intensity during Maintenance, Toxicities and Relapse Risk in Children with Acute Lymphoblastic Leukemia (ALL): COG-AALL03N1 Report

Introduction: Current COG protocols for childhood ALL recommend increasing 6-mercaptopurine (6MP) and methotrexate (MTX) dose intensity (DI=prescribed therapy dose/ planned protocol dose) to &amp;gt;100% during maintenance for patients exhibiting inadequate myelosuppression (surrogate for systemic exposure to 6MP/MTX). Whether increasing DI &amp;gt;100% (high DI) to achieve myelosuppression is associated with increased toxicity is not clear. Additionally, whether high DI influences relapse risk, and the direction of that association, remains unknown. Nonadherence to 6MP results in inadequate myelosuppression and prompts clinicians to increase the prescribed dose. Nonadherence to 6MP is also associated with relapse (Bhatia, JAMA Onc 2015). Prior literature examining the association between high DI and relapse risk did not consider adherence to chemotherapy. Here, we examined whether high 6MP/MTX DI affects toxicity or relapse, taking 6MP adherence into consideration. Methods: We used data collected by COG-AALL03N1 (primary aim: 6MP adherence and risk of relapse) to examine the association between high DI and (i) hematologic toxicity, and (ii) relapse risk. Inclusion criteria: (i) age &amp;lt;21y at ALL diagnosis, (ii) receiving maintenance therapy in first remission and &amp;gt;6mo since starting maintenance, (iii) wild-type thiopurine methyltransferase ( TPMT) or nucleoside diphosphate-linked motif 15 (NUDT15) and (iv) objectively measured 6MP adherence for 6mo per patient (using MEMS-TrackCaps). 6MPDI and MTXDI were calculated monthly for 6mo. Updates on vital status, relapse or second neoplasm were collected every 6mo-1y from participating sites for up to 10y. Exposure: ‘high DI’ phenotype: (i) 6MPDI or MTXDI ≥110% at any time during the first 4 study months, or (ii) 6MPDI or MTXDI 100% to 110% at study enrollment and ≥25% increase over the first 4 study months. All other patients were categorized as having ‘normal DI’. Outcomes: (i) hematologic toxicity (absolute neutrophil count &amp;lt;500 cells/µL, platelet count &amp;lt;50,000 cells/mm 3, or treatment interruption due to low ANC/platelets) during the subsequent 2 study months (months 5 and 6); and (ii) ALL relapse any time after month 4. We used logistic regression to examine the association between high DI and hematologic toxicity, adjusting for age at study entry, sex, race/ethnicity. The association between DI and relapse was estimated using proportional sub-distribution hazard regression models, adjusting for age at study entry, blast cytogenetics, time from start of maintenance, and treatment interruptions. Analyses were stratified by 6MP adherence (adherers: median adherence ≥85%; non-adherers: median adherence &amp;lt;85%). Adherence was included in both models to account for residual confounding. Results: Characteristics of the 410 eligible participants are summarized in the Table; the cohort was followed for a median 7.9y (range, 0.2-13). There were no significant differences between patients with normal (71.5%) vs high (28.5%) DI. Patients with high DI had lower median 6MP adherence (94.6% vs 97.0%, P=0.02). Hematologic DLT: As shown in the Figure, the proportion of patients with hematologic toxicities was significantly higher among adherers with high DI compared with adherers with normal DI (38.1% vs 18.5%, P=0.0003). In contrast, the proportion of patients with hematologic toxicities was not significantly different by DI status among non-adherers (18.5% vs 10.5%, P=0.4). Multivariable analysis revealed that high DI was associated with 2.9-fold greater odds of hematologic toxicity among adherers (95%CI=1.6-5.1, P&amp;lt;0.001) and a non-significant 2.1-fold greater odds of hematologic toxicity among non-adherers (95%CI=0.4-10.1, P=0.4). Relapse risk: The adjusted hazard of relapse among adherent patients exposed to high DI was 2.2-fold greater (95%CI=1.0-5.1, P=0.06) than adherent patients exposed to normal DI after adjusting for covariates. In contrast, the hazard of relapse among non-adherent patients exposed to high DI (vs. normal DI) was not elevated (HR=0.9, 95%CI=0.2-3.8, P=0.8). Conclusions: High antimetabolite dose intensity in children with ALL who adhere to oral 6MP during maintenance therapy is associated with higher odds of hematologic toxicities as well as increased hazard of relapse. These findings inform clinicians about the issues related to dose escalation beyond protocol doses, especially among adherent patients.

Cerebral Spinal Fluid Attenuates the Efficacy of Methotrexate Against Acute Lymphoblastic Leukemia Cells

The anti-folate methotrexate is a critical component of acute lymphoblastic leukemia (ALL) therapy. In addition to systemic administration, methotrexate is given intrathecally, or directly into the cerebral spinal fluid (CSF) via lumbar puncture, for central nervous system (CNS) leukemia treatment and prophylaxis. While IT methotrexate played a critical role in improving outcomes for ALL, CNS ALL relapse remains a major cause of treatment failure and therapy related morbidity. However, attempts to develop more efficacious and less toxic CNS ALL therapies have been largely unsuccessful and IT methotrexate has remained the standard of care for 60+ years. Based on our prior work showing that ALL cells are more poised to undergo apoptosis in nutrient poor CSF, we initially hypothesized that ALL chemosensitivity will be increased in CSF (Basile et al., 2020). While this was confirmed for several ALL drugs including cytarabine and anthracyclines, we strikingly found that methotrexate was significantly less efficacious and potent against ALL cells in CSF relative to standard tissue culture media or the more physiologically relevant human plasma-like media (HPLM). CSF also attenuated the sensitivity of ALL cells to other anti-folates including raltitrexed, trimetrexate, and pralatrexate. To define the mechanism(s) underlying this methotrexate resistance induced by CSF, we explored previously well-described mechanisms of methotrexate resistance in leukemia and other cancers. However, to date this work suggests that the molecular etiology of this CSF-induced relative methotrexate resistance is not entirely explained by diminished leukemia proliferation in CSF, altered methotrexate cellular influx/efflux, methotrexate metabolism, folate analog rescue, dysregulated expression of methotrexate target proteins, or compensation by nucleotide salvage pathways. To complement our work examining known mechanisms of methotrexate resistance, we also used a more discovery-based approach and compared the gene expression patterns of leukemia cells in CSF versus tissue culture media. Preliminary bioinformatic analyses identified dysregulation of multiple genes involved in the integrated stress response (ISR) and unfolded protein response (UPR) pathways in leukemia cells in CSF. The ISR/UPR are mechanisms by which cells adapt to diverse stress stimuli in the microenvironment, including potentially nutrient poor CSF which is low in glucose, proteins, and lipids relative to plasma. The hallmark event in this pathway is the phosphorylation of the translation initiation factor eIF2α, which inhibits global protein synthesis and enables the translation of selected genes that together enable cell survival. Supporting our gene expression data, ALL cells in CSF showed increased phosphorylation of eIF2α and a decrease in global protein synthesis. Intriguingly, it has been shown that activation of the UPR can divert metabolites from glycolysis to mitochondrial one-carbon metabolism with resulting resistance to anti-folates such as methotrexate (Reich et al., 2020). Accordingly, we next tested the effect of UPR/ISR activation on leukemia cell sensitivity to methotrexate in tissue culture media. Activation of the UPR with thapsigargin, a sarco/endoplasmic reticulum Ca 2+ ATPase (SERCA) inhibitor that triggers ER stress, increased methotrexate resistance in leukemia cells. Similarly, BtdCPU a small-molecule activator of heme regulated inhibitor (HRI) kinase that phosphorylates eIF2α and activates the ISR, also enhanced leukemia resistance to methotrexate. Building upon these results, current investigations are focused on testing the role of UPR/IST activation in methotrexate resistance in leukemia cells in CSF and modulating this pathway to overcome resistance. While methotrexate is clearly an efficacious and critical component of CNS leukemia treatment and prophylaxis, we have shown that CSF attenuates the overall efficacy of methotrexate in targeting leukemia cells. Moreover, we anticipate that our current work defining the mechanisms driving this resistance may identify novel approaches for maximizing methotrexate efficacy and more completely eradicating leukemia cells in CSF and the CNS. Finally, this work highlights the importance of critically evaluating even long-established standards of care.

Development of a Novel Methotrexate-Related Neurotoxicity Risk Score in Pediatric Acute Leukemia: A Report from the Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium

Introduction: Methotrexate (MTX) chemotherapy is a critical component of contemporary pediatric acute lymphoblastic leukemia (ALL) treatment regimens. However, intrathecal (IT) and intravenous (IV) MTX can result in dose-limiting acute neurotoxicity, which has been associated with an increased risk of ALL relapse. Emerging data suggest the likelihood of MTX neurotoxicity is elevated in Latino patients and those diagnosed at older age or treated with high-dose MTX (&amp;gt; 1g/m2); however, there are no established methods for identifying those at greatest risk. Therefore, we used machine learning algorithms to develop a neurotoxicity risk prediction model in a diverse, multi-ethnic cohort of pediatric patients with ALL. Methods: The Reducing Ethnic Disparities in Acute Leukemia (REDIAL) Consortium enrolls patients diagnosed with ALL from six participating treatment centers in the Southwestern U.S. This interim analysis included pediatric patients (age &amp;lt;20 years) diagnosed and treated for ALL at Texas Children's Hospital (2005-2019). Individuals diagnosed with infant leukemia (&amp;lt;1 year of age) and/or with preexisting neurologic disease were excluded. We retrospectively reviewed medical records to identify clinical, sociodemographic, and Common Terminology Criteria for Adverse Events (CTCAE) grading of toxicities such as transaminitis and hyperbilirubinemia. Address information at the time of diagnosis was geocoded and aligned to the American Community Survey at the census-tract level to define residential social determinants of health (SDOH). Cases of MTX neurotoxicity were identified by manual review of records for any patient who underwent brain MRI imaging during ALL therapy. Cases of acute MTX neurotoxicity were defined following Ponte di Legno Delphi Consensus definitions as neurologic episodes (e.g., seizure, stroke-like symptoms, altered mental status) occurring within 21 days of IV or IT MTX with no other identifiable underlying cause. Demographic and clinical factors were compared between cases of acute MTX-related neurotoxicity and controls using logistic regression models to estimate odds ratios (OR) and 95% confidence intervals (CI). The dataset was randomly split with 80% of observations used in the training stage and 20% reserved for testing. Random forest algorithms with boosting and down sampling were grown using 5-repeat, 10-fold cross validation to optimize tuning parameters. Model performance was evaluated using test and train error rate, area under the curve of the receiver operating characteristic (AUC-ROC), sensitivity, and specificity. Results: A total of 770 patients were eligible and met inclusion criteria. Patients were a mean age of 7.0 years at diagnosis, 54% male, 55% Latino and 45% treated with high-risk protocols. Acute MTX neurotoxicity developed in 134 (17.4%) of patients. In logistic regression models, neurotoxicity odds increased with older age at diagnosis (OR = 1.20, 95% CI: 1.15-1.26), Latino ethnicity (OR = 2.14, 95% CI: 1.38-3.38), treatment on high-risk protocols (OR=4.32, 95% CI: 2.75-6.99), obesity at diagnosis (vs normal weight, OR = 2.54, 95% CI: 1.51-4.22), and CTCAE grade 3 or higher transaminitis (OR = 2.02, 95% CI: 1.03-4.47) or hyperbilirubinemia (OR = 4.71, 95% CI: 1.21-18.41) during induction therapy. Overall, the random forest machine learning algorithm resulted in an AUC-ROC of 0.79 with an error rate of 0.26 in both the training and test sets. The overall sensitivity was 0.71, with a specificity of 0.67. Recognizing ethnic disparities in MTX neurotoxicity may exist, random forest models were generated stratifying on ethnicity (Figure 1), which yielded slightly better performance in non-Latino patients (AUC-ROC = 0.77) than Latino patients (AUC-ROC = 0.73). Conclusions: This interim analysis of data from the REDIAL Consortium demonstrates the potential utility of machine learning algorithms to develop a novel risk prediction model for acute MTX-related neurotoxicity. Efforts to expand this work within the larger REDIAL cohort (n&amp;gt;2,000) and incorporate inherited genetic data are ongoing. Ultimately, this work may inform efforts to preemptively risk-stratify patients and deliver targeted interventions to vulnerable individuals.

Dasatinib and CAR-T Cell Therapy for Newly Diagnosed Ph-Positive Acute Lymphoblastic Leukemia in Adults

Introduction The use of tyrosine kinase inhibitors has improved outcomes of Ph-positive Acute lymphoblastic leukemia (ALL), but combinations with other agents are needed to achieve molecular response. CAR-T cell therapy has made a breakthrough in refractory or relapsed ALL, but has not yet been applied in newly diagnosed patients. Methods We conducted a phase 2 single-group trial of first-line therapy in adults with newly diagnosed Ph-positive ALL. Dasatinib in combination with a two-week vincristine and glucocorticoids regimen were administered, followed by sequential infusions of CD19 and CD22 CAR-T cells. All patients received single-agent dasatinib maintenance after CAR-T cell therapy. The primary endpoint was complete molecular response (defined as undetectable BCR/ABL1 transcript with a sensitivity of 0.001%) in the bone marrow after this treatment. Here we report initial results from this study. Results At the cut-off date of 31 May 2023, 18 patients have received CD19 CAR-T cell infusions, and 14 of these patients have received subsequent CD22 CAR-T cell infusions. At the end of induction therapy, the complete hematologic remission rate was 100%, and 27.8% (5/18) of the patients had a complete molecular response. The percentage of complete molecular response increased to 72.2% (13/18) after CD19 CAR-T cell therapy, and increased further to 76.9% (10/13) after CD22 CAR-T cell therapy (1 patient has not been evaluated). Notably, of the 5 patients who did not achieve complete molecular response after CD19 CAR-T cell therapy, 4 have received CD22 CAR-T cell therapy, of which 1 eventually achieved complete molecular response and 2 experienced relapses. One patient had a CD19+ CD22+ relapse accompanied by mutations in BCR/ABL1 (F317L and Y253H) and the other patient had a CD19dim CD22+ relapse. After a median follow-up of 13.5 months, 16 patients remained in complete hematologic remission, and 14 patients remained in sustained complete molecular response. No patient received allogeneic stem cell transplantation. No grade 3 or higher cytokine release syndrome or Immune effector cell-associated neurotoxicity syndrome was observed during CAR-T cell therapies. Conclusions Dasatinib in combination with CAR-T cell therapy has enabled chemotherapy-free treatment in newly diagnosed Ph-positive ALL. This treatment is characterized by high complete molecular response, high long-term survival, low toxicity and short treatment cycles.

A Real-World Single-Center Report on the Effectiveness and Safety of Blinatumomab Treatment on Pediatric Acute Lymphoblastic Leukemia in China

Background: Studies overseas have demonstrated blinatumomab benefits pediatric acute lymphoblastic leukemia (ALL), but the experience is limited in China. Methods: We retrospectively collected 28 pediatric ALL patients in our center who received blinatumomab treatment since August 2021. All patients were diagnosed with B-ALL with CD19 expression on cell surface. Patients were divided into three groups: clearance of minimal residual disease (MRD) in first complete remission (MC, 18/28), supplement therapy during chemotherapy intolerance (IC, 3/28) and reinduction therapy for refractory or relapsed ALL (RR, 7/28). Results: The age of 28 patients (16 males and 12 females) ranged from 0.6 to 16.4 years (median, 11.0 years). BCR::ABL1 fusion was found in 6 patients in MC group and 1 patient in RR group. The reasons for chemotherapy intolerance included pancreatitis, infection, and endocarditis. The median interphase from diagnosis to blinatumomab was 3.7 (range: 0.7 to 39.8) months, 1.4 (range: 1.1 to 16.8) months and 29.0 (range: 4.9 to 62.1) months in MC, IC and RR groups, respectively. Most patients accepted 14 to 28 days of uninterrupted infusion except 1 patient in MC group received 7 days treatment for economic issue and 2 patients in MC group discontinued therapy for severe reaction in 1 or 2 days. 7 patients received 1 to 3 more cycles of blinatumomab if MRD decreased after the first cycle. In MC group, the median MRD level in bone marrow before blinatumomab, detected by flow cytometry (FC) or by real time PCR (RT-PCR) if recurrent fusion genes were positive, was 0.145% (range: 0.01% to 4.00%). MRDs were turned negative in 13 patients (72.2%) by both FC and RT-PCR, while the MRDs in the other 5 patients with BCR::ABL1 fusion gene, of whom 3 were positive in both FC and RT-PCR and 2 were only positive in RT-PCR, wereturned negative in FC but still positive in RT-PCR. In terms of safety, one patient developed grade 4 immune effector cell associated neurotoxicity syndrome on the second day of infusion. The most common reaction was fever in 9 cases in cycle 1 (9/18). In IC group, all 3 patients with negative MRD before treatment maintained their negative status, with only fever occurring (3/3) during the early stage of infusion. In RR group, the median MRD level before treatment was 8.37% (range: 0.08% to 78.3%). 4 patients (57.1%) with lower MRD (0.08% to 8.37%) by FC before blinatumomab attained MRD negativity, while 3 patients (42.9%) with higher MRD (22.64% to 78.3%) failed. The patient with BCR::ABL1 fusion gene turned MRD negative by FC after blinatumomab, but remained positive by RT-PCR. Two patients (2/7) had cytokine release syndrome of grade 2, and 3 cases only had fever. No other severe or fetal adverse reactions were observed. Conclusions: Blinatumomab is an effective treatment for B-ALL MRD cleanup with a good safety profile. It may, however, not benefit patients with R/R B-ALL with high tumor loads before blinatumomab, and those who carry BCR::ABL1 fusion gene. Studies with a larger sample size are needed to confirm the results.

Loss of p53 Impairs Death Receptor Expression and Confers Resistance to CD19-Directed CAR T-Cell Therapy in B-Cell Precursor Acute Lymphoblastic Leukemia

Background In recent years, new therapy strategies such as the antibody-drug conjugate inotuzumab ozogamicin, the bi-specific T-cell engager blinatumomab, and chimeric antigen receptor (CAR) T-cells have been introduced to salvage relapsed precursor B acute lymphoblastic leukemia (ALL). However, recent evidence indicates that these new therapies are ineffective in TP53-aberrant ALL, although the mechanism remains unclear. TP53 is the most frequently mutated gene in cancer, but in ALL, mutations or deletions affecting TP53 are rare, with an incidence of only 3% at diagnosis. However, at relapse, TP53 aberrations are found in approximately 12% of the patients and predict a very poor outcome. Consequently, relapsed TP53 deleted ALL is now classified as ‘very high risk’. Since p53-mediated apoptosis is an endpoint for many (cytotoxic) drugs, loss of p53 function induces therapy resistance to classical chemotherapeutics. Hence, there is a clear clinical need for more effective strategies to treat TP53 aberrant relapsed ALL. Methods Using CRISPR/Cas9, we introduced frameshift mutations in the TP53 gene to generate isogenic wild type and knockout models in TP53 WT ALL cell lines Nalm6 and RCH-ACV. Additionally, we prepared CD19-directed CAR T-cells with a 4-1BB co-stimulatory domain from three healthy donors by isolating, transducing, and expanding CD4+ and CD8+ T-cells separately. With flow cytometry, we assessed survival of p53 WT and p53 KO leukemic cells in the presence of CD4+ and CD8+ CAR T-cells at a 1:1 CD4:CD8 ratio. Moreover, we performed mRNA profiling by qRT-PCR and cell membrane profiling by flow cytometry to determine how loss of p53 affects CAR T mediated killing. Initial findings in cell lines were then validated in patient-derived xenografts. Results We observed that loss of p53 led to up to a 35% decrease in killing by overnight CAR T treatment in both cell line models (Figure 1A). Although loss of p53 has been linked to reduced cell surface expression of CD19 (Pan et al., 2020, Leukemia), no changes in CD19 expression were observed in response to p53 loss. In search for an explanation for the diminished killing, we performed mRNA profiling and found a reduced expression of death receptors CD95/Fas and DR5/TRAILR2 in p53-deficient cells, which was confirmed at the protein level with flow cytometry (Figure 1B). Indeed, CRISPR/Cas9 mediated loss of CD95/Fas expression in p53 wild type cells reduced CAR T mediated cell killing, consistent with a key role for CD95/Fas in T-cell mediated killing. Conversely, treatment of p53 proficient cells with MDM2 inhibitors induced expression of CD95/Fas and DR5/TRAILR2 (Figure 1B), which translated into enhanced killing of target cells. Most of these observations have already been recapitulated in a diagnosis-relapse pair of patient-derived cells in which the diagnosis was p53wild typeand the relapse was p53 deficient (Figure 1A-B). We observed lower baseline mRNA expression of CD95/Fas and DR5/TRAILR2 in p53-deficient cells, accompanied by a 50% reduction in killing relative to the p53 wild type controls. Conversely, MDM2 inhibition increased death receptor expression only in p53-proficient cells. The ongoing experiments validating enhanced killing after MDM2 inhibition in patient-derived cells will be presented during the meeting. Conclusions Loss of p53 impairs expression of CD95/Fas and DR5/TRAILR2, thereby protecting ALL cells from CAR T induced cell death. In addition, our results indicate that the p53-controlled expression of these receptors may be exploited to increase the efficacy of CAR T-cell therapy in p53-proficient patients.

Phase 2 study of inotuzumab ozogamicin for measurable residual disease in acute lymphoblastic leukemia in remission

AbstractThe detection of measurable residual disease (MRD) is the strongest predictor of relapse in acute lymphoblastic leukemia (ALL). Using inotuzumab ozogamicin in the setting of MRD may improve outcomes. Patients with ALL in first complete remission (CR1) or beyond (CR2+) with MRD ≥ 1 × 10−4 were enrolled in this phase 2 trial. Inotuzumab was administered at 0.6 mg/m2 on day 1 and 0.3 mg/m2 on day 8 of cycle 1, then at 0.3 mg/m2 on days 1 and 8 of cycles 2-6. Twenty-six consecutive patients with a median age of 46 years (range, 19-70 years) were treated. Nineteen (73%) were in CR1 and seven (27%) in CR2+; 16 (62%) had Philadelphia chromosome–positive ALL. Fifteen (58%) had baseline MRD ≥ 1 × 10−3. A median of 3 cycles (range, 1-6) were administered. Eighteen (69%) patients responded and achieved MRD negativity. After a median follow-up of 24 months (range, 9-43), the 2-year relapse-free survival rate was 54% and the 2-year overall survival rate was 60% in the entire cohort. Most adverse events were low grade; sinusoidal obstruction syndrome was noted in 2 patients (8%). In summary, inotuzumab ozogamicin resulted in favorable survival, MRD negativity rates, and safety profiles for patients with ALL and MRD-positive status. This study was registered at www.ClinicalTrials.gov as #NCT03441061.