Adult B-cell Acute Lymphoblastic Leukemia Patients Research Articles

SPAG6 regulates cell proliferation and apoptosis via TGF-β/Smad signal pathway in adult B-cell acute lymphoblastic leukemia.

Adult B-cell acute lymphoblastic leukemia (B-ALL) prognosis remains unsatisfactory, and searching for new therapeutic targets is crucial for improving patient prognosis. Sperm-associated antigen 6 (SPAG6), a member of the cancer-testis antigen family, plays an important role in tumors, especially hematologic tumors; however, it is unknown whether SPAG6 plays a role in adult B-ALL. In this study, we demonstrated for the first time that SPAG6 expression was up-regulated in the bone marrow of adult B-ALL patients compared to healthy donors, and expression was significantly reduced in patients who achieved complete remission (CR) after treatment. In addition, patients with high SPAG6 expression were older (≥ 35years; P = 0.015), had elevated white blood cell counts (WBC > 30 × 109/L; P = 0.021), and a low rate of CR (P = 0.036). We explored the SPAG6 effect on cell function by lentiviral transfection of adult B-ALL cell lines BALL-1 and NALM-6, and discovered that knocking down SPAG6 significantly inhibited cell proliferation and promoted apoptosis. We identified that SPAG6 knockdown might regulate cell proliferation and apoptosis via the transforming growth factor-β (TGF-β)/Smad signaling pathway.

Unraveling the Mechanism of Action of Bispecific T-Cell Engagers in B-Cell Acute Lymphoblastic Leukemia Using Advanced Single-Cell Multiomics

Background Bispecific T-cell engagers (BiTEs) stimulate T lymphocytes proximate to tumor cells, inducing T-cell stimulation and tumor killing. Blinatumomab, an anti CD3-CD19, was the first to be approved with overall response rates of up to 80% in refractory B-cell Acute Lymphoblastic Leukemia (B-ALL). To overcome resistance and to develop next-generation BiTEs, we need to build on blinatumomab's success and better understand BiTEs mode of action and interaction with the tumor microenvironment (TME). Here, we apply advanced multiomics to examine blinatumomab's activation signatures and the sustained dynamics in the tumor and bone marrow (BM) immune TME. Methods Physically interacting Cells sequencing (PIC-seq) is an advanced multiomics technology deciphering the crosstalk between the cellular components of an immunological synapse (Cohen et al., 2022; Giladi et al., 2020). To assess Immediate activation signatures, we applied PIC-seq on a model of B-ALL cell lines (RS4;11, NALM-6) and lymphocytes obtained from healthy subjects, activated by blinatumomab, compared to no-treatment and activation with anti CD3-CD28 antibodies. To examine the Sustained effects on the immune TME, we performed a longitudinal single-cell RNA sequencing of the bone BM of adult B-ALL patients, before and after treatment with blinatumomab in the Division of Hematology in the Tel Aviv Sourasky Medical Center in 2021-22. Results Immediate activation Applying PIC-seq on n=16,543 CD3 and CD19+ cells, we identified the distinct gene expression of ‘blinatumomab-activated lymphocytes’ (Figure 1). Blinatumomab induced cellular synapses composed of specific T lymphocytes subsets along the activation continuum, namely: effector T cells (CCL5, GNLY, NKG7), early IFN-G activation (IRF1, GBP5), activated cytotoxic (Xcl1-2, IFN-G) and proliferating T cells (CD69, CCND2) . ‘Blinatumomab-activated lymphocytes’ were characterized by a unique activation signature: upregulation of cytotoxicity (Xcl1, IFN-G, GNLY), co-stimulation and B-T cells crosstalk (CD40, CD27, TNFRSF18), immune recruitment (CXCL10, CCL4) and antigen-presentation (TNFSF14, ITGB2) pathways. Late synapses also expressed immunoregulatory molecules (TNFAIP8L2). This signature differed from classical anti CD3-CD28 induced activation and is independent of the donor and the target-cell identity. The malignant cells' response varied: RS4;11 cells manifested cellular senescence, while NALM-6 upregulated INFG-induced apoptotic pathways, suggesting indirect killing in the mechanism of action of BiTEs. Data on the introduction of primary B-ALL patients' cells will be presented at the ASH. Sustained effects We profiled >11,000 cells from three patients: Patient 1, 31-year-old (y/o) female, primary refractory B-ALL (50% BM blasts), attaining transient MRD negativity. Patient 2, 71-y/o male, primary refractory Ph+ B-ALL (74% BM blasts) achieving reduction in MRD following first cycle. Patient 3, 71 y/o, Ph+ B-ALL, treated as consolidation therapy, achieving MRD negativity. Blinatumomab induced a dramatic perturbation in the lymphocytic and myeloid compartments of the BM and was highly patient-specific ( Figure 2). The BM lymphocytic compartment prior to initiation of blinatumomab in molecular remission (patient 3) was characterized by active T and Natural Killer cell states, compared to an abundancy of naïve lymphocytes in active disease (patients 1 and 2). There were no signs of T-cell exhaustion pre or post treatment in all patients. Post-treatment, CD8 T-Central Memory cells proliferated in all patients. Patients treated for active disease (patients 2 and 3), had an expansion of the Tregs population post-treatment. In the myeloid compartment, patients with active disease had more non-classical monocytes, known to correlate with poor prognosis. These were replaced by classical monocytes following treatment, in addition to the emergence of a macrophage-precursor population. Data on the BM and peripheral blood dynamics of an additional six patients will be presented at the ASH. Conclusions We present an advanced single cell dissection of blinatumomab-induced target-effector interaction, providing novel insights into the mechanism of action and TME dynamics to guide patient selection and next generation BiTEs. A larger patients' cohort and introduction of patients' cells to the PIC-seq in vitro model will be presented at the ASH.

Impact of Salvage and Bridging Therapy in Adult Patients with Refractory B-Cell Acute Lymphoblastic Leukemia (B-ALL) Referred for Anti-CD19 CAR T-Cell Therapy: An Intention to Treat Analysis

Background: Prognosis of relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (ALL) is poor, particularly after allogeneic hematopoietic cell transplantation (alloHCT). In this setting, several CAR T-cell products targeting CD19 (CART19) have been able to achieve complete response (CR) rates of 70 to 90%. However, a significant proportion of these patients still relapse. Several studies focus on the effect of the CART19 product on efficacy, however, information on how salvage therapy (ST) and bridging therapy (BT) can modulate the outcomes of CART19 therapy is scarce. Methods: We report the outcomes of all adult patients with R/R B-ALL intended for treatment (aphaeresis performed) with available CART19 products in a single institution from Jul 2017 to Jul 2023. This includes patients intended to receive the academic varnimcabtagene autoleucel (var-cel) in the CART19-BE-01 trial and the consecutive compassionate use and hospital exemption programs, as well as with commercially available tisagenleuceucel (tisa-cel). Lymphodepletion was performed with fludarabine (90 or 120 mg/m 2) and cyclophosphamide (900 or 1000 mg/m 2), followed by the infusion var-cel or tisa-cel, respectively. We analyzed all ST (treatment administered after last relapse before CART19-apheresis) and BT (treatment administered after apheresis and before CART19 infusion) performed, and analyzed the impact of BT on PFS and OS after apheresis. Results: A total of 74 adult B-ALL patients underwent leukapheresis and CART19 (var-cel/tisa-cel) production. At screening patients had a median age of 34 years (19-78), 45% were females, with a median of 3 prior lines of therapy (2-7) including inotuzumab (69%), blinatumomab (27%) and allo-HCT (84%). After last relapse, 92% of patients received ST with a median of 1 (0-3) treatment line, including inotuzumab (48%), high-dose chemotherapy (28%), low-dose chemotherapy (21%), TKIs (12%), blinatumomab (9%), radiotherapy (7%) and DLIs (4%). The overall response to ST prior apheresis was MRD-negative CR (28%), MRD-positive CR (22%), partial response (4%) and progressive disease (PD) in 46%. After apheresis was secured, BT was performed in 76% of patients with a median of 1 (0-2) bridging line, including low-dose chemotherapy (44%), intrathecal therapy (23%), high-dose chemotherapy (15%), TKIs (15%), inotuzumab (14%), radiotherapy (3.5%), blinatumomab (1.8%) and DLIs (1.8%). BT was not administered in 24% (8/74) of patients mainly due to morphological remission at screening (83%) and frailty (11%). The overall response to BT prior CART19 infusion was MRD-negative CR (31%), MRD-positive CR (12%), partial response (7%) and progressive disease (47%), with a 3% treatment related mortality (TRM) events attributed to BT. Inotuzumab administration occurred either as ST or BT to CART19 in 86% of patients (the remaining 14% was previouly given as bridge to allo-HCT), and was able to achieve MRD-negative CR in 42% of patients. The overall control of the disease after BT either worsened (51%), remained similar (14%), or improved (35%). After this, 12% (n=9) of CART19 treatments were not performed due to progressive disease (33%), TRM (22%), therapeutic alternative (22%), and production failure (11%). Infused patients achieved an MRD-negative CRR of 90% with a median PFS of 11,2 months. There were no differences in OS between patients with ≥5% or <5% bone marrow (BM) blast counts either before apheresis (ITT, figure 1) or after BT prior to CART19 infusion. However, despite the lack of apparent impact of this disease burden categorization on the OS at both timepoints, a statistically significant difference was observed after categorizing patients regarding the response to BT (figure 2), with a median PFS of 6.6 vs 18.6 months if the overall disease status of the patients either worsened or remained stable/improved after BT (p=0.0002). Conclusions: To the best of our knowledge this could be one of the first studies focusing on the impact of ST and BT in adult patients with R/R B-ALL referred for CART19 therapy. These results suggest that the potentially synergistic impact of bridging therapy may be mediated more by the modulation exerted by BT on the proliferative kinetics of the disease rather than on the absolute tumour burden of the patient. More detailed results on the independent impact of each type of BT will be provided in the final presentation.

Association of Minimal Residual Disease by a Single-Tube 8-Color Flow Cytometric Analysis With Clinical Outcome in Adult B-Cell Acute Lymphoblastic Leukemia: A Real-World Study Based on 486 Patients.

Minimal/measurable residual disease (MRD) measured by molecular and multiparametric flow cytometry (MFC) has been proven to be predictive of relapse and survival in patients with B-cell acute lymphoblastic leukemia (B-ALL). A universally applicable antibody panel at a low cost but without compromising sensitivity and power of prognosis prediction in adult B-ALL remains unestablished. To report our experience of using a single-tube 8-color MFC panel to measure the MRD status as a prognostic indicator in adult B-ALL patients. We retrospectively analyzed the characteristics, MRD status, and prognosis of adult B-ALL based on a large real-world cohort of 486 patients during a 10-year period. MRD assessed by MFC and polymerase chain reaction (PCR) assays for BCR-ABL+ patients showed concordant results in 74.2% of cases. MRD- status by our MFC panel could clearly predict a favorable relapse-free survival (RFS) and overall survival (OS) both at the end of induction and at the end of 1 consolidation course. Patients with continuous MRD- and with at least 1 MRD- result showed a favorable RFS and OS compared with those with at least 1 MRD+ result and continuous MRD+, respectively. The single-tube 8-color MFC panel demonstrated a low cost, decent sensitivity, and comparability with polymerase chain reaction-MRD but an excellent performance in predicting RFS and OS, and thus could potentially be taken as a routine indicator in the evaluation of the treatment response for adult patients with B-ALL.

Better Prognosis of Dominant-Negative Type of IKZF1 Deletion in BCR-ABL-positive Adult B-Cell Acute Lymphoblastic Leukemia

IntroductionIKZF1 codes Ikaros, which is a member of a family of zinc finger proteins that is required for normal lymphopoiesis. IKZF1 alterations in cases of B-cell acute lymphoblastic leukemia (B-ALL) were mainly analyzed in a pediatric cohort and showed an association with poor prognosis. In adults IKZF1 alterations are found in approximately 50% of B-ALL cases, and 65% of cases with BCR-ABL-positive B-ALL. IKZF1 deletion have several different types of deletions. Deletion of exons 4 to 7 (Δ4-7) leads to nonfunctional isoforms that do not bind DNA. However, they can still dimerize with residual normal isoforms, suppressing the function of the normal Ikaros protein expressed from the nondeleted allele, a so-called "dominant-negative” (DN) effect. Other deletions lead to loss of function (LOF) of Ikaros. The impact of DN and LOF type of IKZF1 deletion on prognosis in adult B-ALL patients has not been elucidated. We evaluated the impacts of IKZF1 deletion types on overall survival (OS) in our cohort. Patients and Methods Hokkaido Leukemia Net (HLN) is prospective cohort study collecting acute leukemia samples from hospitals of North Japan Hematology Study Group (NJHSG) covering Hokkaido, the northernmost island of Japan. In this study, we focused on newly diagnosed adult B-ALL patients. Bone marrow or peripheral blood samples from newly diagnosed B-ALL patients were screened by a fluorescence in situ hybridization (FISH) probe for detecting IKZF1 deletion (Hashiguchi J. J Mol Diagn. 2018). Then DNA specimens from IKZF1 deletion-positive patients were screened for the 4 most common intragenic IKZF1 deletions, Δ4-7, Δ2-7, Δ2-8 and Δ4-8, by polymerase chain reaction (PCR). Samples in which IKZF1 deletion was detected by FISH but in which the types of deletions were not identified were defined as "other". We categorized the patients into a DN group that had Δ4-7, LOF and other group, and wildtype (WT) group based on the types of IKZF1 deletion. This study was conducted in accordance with the Helsinki Declaration and was approved by the institutional review boards. Results Overall, 116 patients with newly diagnosed B-ALL were enrolled in HLN between August 2014 and December 2021 (age range, 17-90 years; median age ,59 years; 55 males and 61 females; 60 BCR-ABL-positive patients and 56 BCR-ABL-negative patients). IKZF1 deletion was detected in 53 cases including 6 cases with bi-allelic deletion. IKZF1 deletions were detected in 68.3% of BCR-ABL-positive B-ALL cases and 21.4% of BCR-ABL-negative B-ALL cases. DN/LOF and other ratio was larger in BCR-ABL-positive B-ALL cases than in BCR-ABL-negative B-ALL cases (20/21 vs 3/9). In patients with BCR-ABL-positive B-ALL, patients with the DN type of IKZF1 deletion had a significantly longer OS than that in the WT group. The 3-year OS rates in the DN, LOF and other, and WT groups were 100%, 60.4%, and 49.9%, respectively (Figure A). Distribution of age, sex, percentage of allogenic hematopoietic stem cell transplantation (allo-HSCT) were not significantly different between the three groups. Survival was analysed by univariate analysis including age, sex, WBC counts, complex karyotype, IKZF1 deletion type and allo-HSCT. Age≥65 was associated with poor OS (P=0.0078) and DN type of IKZF1 deletion was associated with favorable OS (P=0.026). Multivariate analysis showed that older age and DN type of IKZF1 deletion were independently associated with OS (age≥65: HR, 3.510; 95% CI, 1.327 to 9.289, P=0.011; DN type of IKZF1 deletion: HR, 0.200; 95% CI, 0.046 to 0.884, P=0.034; Cox regression). In patients with BCR-ABL-negative B-ALL, there was no statistically significant difference in OS between the three groups, whereas the LOF and other group showed a dismal prognosis. The 3-year OS rates in the DN, LOF and other, and WT groups were 100%, 0%, and 56.5%, respectively (Figure B). Conclusion The prognostic impact of IKZF1 deletion might differ in BCR-ABL-positive and BCR-ABL-negative B-ALL cases and might also depend on the type of deletion. DN type of IKZF1 deletion is independently associated with favorable prognosis in adult BCR-ABL-positive B-ALL patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Younger Matched Unrelated Donors Confer a Decreased Relapse Risk As Compared to Older Sibling Donors for Adult B-Cell ALL Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

Background: The incidence of acute lymphoblastic leukemia (ALL) has increased due to aging population and the median age at diagnosis is 56 years among adults. Allogeneic hematopoietic cell transplant (alloHCT) offers cure for ALL patients, however, disease relapse remains a major issue. Human leukocyte antigen (HLA)-matched sibling donors (MSD) are considered the ideal donor type, mainly due to lower incidence and severity of graft-versus-host-disease (GVHD) and improved disease-free survival (DFS) in ALL. However, siblings are also likely to be older, often with higher comorbidities, and adult ALL patients typically undergo reduced-intensity conditioning and need novel strategies to reduce the post-alloHCT relapse risk. While recent data have suggested relapse reduction and survival benefit with younger matched unrelated donors (MUD) in AML and MDS, the impact of donor age on alloHCT outcomes in adult ALL patients remain unknown. Methods: This retrospective cohort study from the Center for International Blood and Marrow Transplant Research database (CIBMTR) data in B-cell ALL patients 50 years or older, undergoing alloHCT from older (>50) MSDs or younger (<35) MUDs between 2011 and 2018, included common allograft types (PB vs BM), conditioning regimens (RIC/NMA vs MAC), and graft-versus-host-disease (GVHD) prophylaxis strategies (FK-based vs CSA-based vs. others). Other exclusion criteria were recipients of ex vivo T-cell depleted grafts, recipients of mismatched unrelated donors, cord blood or identical twin transplants. The primary outcome, compared between the 2 donor age groups, was relapse risk whereas secondary outcomes included non-relapse mortality (NRM), DFS, and overall survival (OS). Cumulative incidence estimates were calculated for competing risks outcomes, including NRM and relapse. The Kaplan-Meier method was used to estimate the probabilities for survival. To evaluate potential risk factors, multivariable cox regression was used, and relevant transplant-related covariates were considered. Interactions between the main effect (donor age group) and significant risk factors were tested. Fine and Gray model was used for NRM and relapse. Given the multicenter nature of the database, center effect was tested for OS by fitting a gamma frailty model. Results: Among 925 eligible patients in the study cohort, 386 underwent alloHCT with an older MSD (median age, 59 [range: 50-75]) whereas 539 received transplant from a younger MUD (median age, 60 [range: 50-77]). In multivariable analysis, younger MUDs conferred a significantly decreased risk of relapse (HR 0.68; 95% CI, 0.53-0.87; p=.002) versus older MSDs (Table 1; Figure 1). The adjusted cumulative incidence of relapse at 5 years was significantly lower with younger MUDs compared to older MSDs (26% vs 37%; p=.001) (Table 2). Younger MUDs conferred an increased NRM compared to older MSDs (HR 1.38; 95% CI, 1.05-1.82; p=.02) (Table1; Figure 1). The adjusted cumulative incidence of NRM at 5 years was also significantly higher in B-ALL patients who underwent alloHCT from younger MUDs compared to older MSDs (31% vs 22%; p=.006) (Table2). There were no differences in OS or DFS rates of alloHCT with younger MUDs vs older MSDs (OS: HR 1.09; 95% CI, 0.90-1.32; p=.37; DFS: HR 0.95; 95% CI, 0.79-1.14; p=.57) (Table 1; Figure 1). The adjusted 5-year OS probability was 48% in younger MUDs (95% CI, 43%-52%) and 51% among older MSDs (95% CI, 45%-56%; p=0.37). The adjusted 5-year DFS probability was 44% with younger MUDs (95% CI, 40%-49%) compared to 42% with older MSDs (95% CI, 37%-47%; p=.59) (Table2). Conclusions: This is the largest study to date performed in a mature, prospectively collected registry cohort that aids in donor selection and found significant relapse reduction in adult B-ALL patients who underwent alloHCT with younger MUDs as compared to older MSDs. The results highlight that younger MUD donor type exerts a stronger GVL effect and should be preferred in patients at a higher risk for post-alloHCT relapse. The higher NRM associated with younger MUDs will need enhanced GVHD prophylaxis, infection preemption and preventative strategies, and supportive cares measures to consolidate the leukemia-free survival. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Abstract 3910: Cellular profiling of leukapheresis and infusion products of patients enrolled in CD19 CAR T cell therapy identifies biomarkers associated with clinical outcomes

Abstract CD19 CAR T cell therapy has emerged as a promising therapy in the treatment of B cell malignancies, such as B cell acute lymphoblastic leukemia (B-ALL). However, questions remain regarding the heterogeneity of the CAR T cell infusion products that lead to differential clinical outcomes and side effects, including cytokine release syndrome and neurotoxicity. The purpose of this study is to identify biomarkers and T cell subpopulations within 1) leukapheresis samples of patients receiving CD19 CAR T cell therapy and 2) pre-infusion manufactured CAR T cell products to identify correlates with clinical outcomes. We hypothesize that different manufacturing practices used to generate CAR T cells from the patient’s leukapheresis T cells drive heterogeneity within the infusion products that drive differential patient outcomes, and that cell intrinsic properties within the leukapheresis T cells drive phenotypic dispositions observed in the infusion products. Leukapheresis samples and pre-infusion CAR T cells were obtained from pediatric and adult B-ALL patients enrolled in CD19 CAR T cell clinical trials. Briefly, leukapheresis T cells from pediatric patients were CD4/8 sorted and then stimulated with CD3/CD28 beads followed by CAR transduction. Pediatric CD4 CAR T cells were cultured with IL-7 + IL-15 while CD8 CAR T cells were cultured with IL-2 + IL-15. CAR T cells from adults were stimulated with LCLs expressing CD19. To identify T cell subpopulations and biomarkers leukapheresis T cells and CAR T cells from each patient were stained with two mass cytometry panels: 1) a phenotype panel of antibodies to characterize surface markers, transcription factors and chemokine receptors and 2) a functional panel of antibodies specific for cytokines to broadly characterize the secretion profile of leukapheresis and CAR T cells upon stimulation with PMA and Ionomycin. Additional multi-omic profiling was performed with CITE-seq and 10X Chromium on leukapheresis samples and CAR T cells of select adult patients to provide in depth analysis on transcriptomic drivers of phenotypes observed within CAR T cell infusion products. We hierarchically clustered leukapheresis T cells and CAR T cells and correlated the abundance of T cell subclusters within each patient to their neurotoxicity grade (0-5). We determined that CD4 CAR T cells that secrete elevated levels of IL-3 upon stimulation correlate with an increased risk of severe neurotoxicity (designated as grades 3-5) within our pediatric cohort. Identification of IL-3 as a driver of neurotoxicity within the CD4 infusion products may inform strategies to improve manufacturing practices used to generate safer CAR T cell products. Citation Format: Tony Chour, Alexandre Hirayama, Ye Zheng, Alyssa Sheih, Summer Zhuang, Ashley Wilson, Vicky Wu, Raphael Gottardo, Cameron Turtle, Rebecca Gardner, Evan Newell. Cellular profiling of leukapheresis and infusion products of patients enrolled in CD19 CAR T cell therapy identifies biomarkers associated with clinical outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3910.

Cross-Sectional Physician Survey on the Use of Minimal Residual Disease (MRD) Testing in the Management of Pediatric and Adult Patients with Acute Lymphoblastic Leukemia (ALL)

Introduction:Acute lymphoblastic leukemia (ALL) is a rare disease that progresses quickly and may be fatal within a few months if untreated. Although the majority of adults and pediatric patients with ALL achieve complete remission (CR) with current chemotherapy regimens, a significant proportion will ultimately have a relapse, particularly in the adult population. Minimal residual disease (MRD) has been demonstrated as a prognostic factor; higher levels of MRD indicate a higher likelihood of relapse. New techniques have been developed to quantitatively detect the presence of MRD in patients who achieve CR. The objective of this study was to explore use of MRD testing in the adult B-cell ALL patient population compared to its use in pediatric B-cell ALL patients, as well as to compare its use in academic versus community settings.Methods:This cross-sectional, non-interventional study used a quantitative survey to explore use of MRD testing among US physicians who treat ALL. Prior to implementation, 2 rounds of qualitative interviews were conducted to develop the content of the quantitative survey (4 in-person interviews and 2 online/phone interviews). Following the qualitative phase, a 20-minute quantitative online survey was conducted with US-based academic hematologists who actively monitor or treat ≥5 B-cell ALL patients and use MRD testing in practice. Physicians self-reported their primary hospital affiliation as being academic- or community-based and were classified as adult or pediatric treaters based on their reported proportion of adult versus pediatric B-cell ALL patients. Descriptive analyses (frequencies and percentages) of survey responses were conducted and Pearson's chi square test was used to assess differences by physician practice setting (academic versus community-based) and by primary patient population (adult versus pediatric).Results:One hundred fifty adult treaters (100 community adult treaters and 50 academic adult treaters) and 30 pediatric treaters (10 community pediatric treaters and 20 academic pediatric treaters) participated in the survey, for a total of 180 physician participants. Physicians used a variety of MRD tests, with flow cytometry being the most frequent choice among both adult and pediatric treaters, followed by polymerase chain reaction and next generation sequencing testing.The use of MRD testing was found to be higher among physicians who primarily treat pediatric patients (93%) than those who treat adult patients (73%) (p<0.05). Among the physicians who primarily treat adults (n=150), the number of patients receiving MRD testing was higher among those receiving treatment from an academic center compared to those from a community setting (84% and 67%, respectively; p<0.01). Academic adult treaters were also more likely to give patients ≥5 tests through the course of disease compared to community adult treaters (16% and 5%, respectively; p<0.05) (Table 1).Pediatric patients commonly received an MRD test during/after induction or upon relapse, while there was no consensus on the timing of MRD tests for adult patients. MRD testing was most common following maintenance treatment phase rather than during treatment (Figure 1). Collectively, physicians often conduct MRD testing after induction or consolidation of treatment.When asked to identify barriers that affected their decisions to conduct MRD tests, a greater proportion of academic adult treaters (32%) reported no barriers to conducting MRD testing compared to community adult treaters (13%) (p<0.01). Community adult treaters were more likely to indicate cost (50%) and lack of insurance coverage (42%) as barriers to MRD testing compared to academic adult treaters (24% each) (p<0.05) (Table 2; Figure 2).Conclusion:In this survey of physicians who treat patients with B-cell ALL and have used any MRD tests, physicians who primarily treat pediatric patients were more likely to conduct MRD testing than physicians who primarily treat adults. Physicians who treat patients with ALL in academic settings were also more likely to perform MRD testing compared with physicians who treat patients in community settings; some of the reasons for differences in MRD testing rates were cost and insurance barriers. Resolving these issues would be critical to improving detection of a molecular relapse in patients with ALL, most importantly among adults and in community settings. [Display omitted] DisclosuresChia:Amgen, Inc.: Employment, Equity Ownership. Delaney:Amgen, Inc.: Consultancy. McNamara:Amgen, Inc.: Consultancy. Kim:Amgen, Inc.: Employment, Equity Ownership. Romanov:Amgen, Inc.: Employment, Equity Ownership.

Economic Burden of Veno-Occlusive Disease (VOD) in Patients with Acute Lymphoblastic Leukemia (ALL) in the US

IntroductionHepatic Veno-occlusive disease (VOD) is a potential life threatening complication of hematopoietic cell transplantation (HSCT) and may also occur after chemotherapy (Negrin et al. 2017). Severe VOD characterized by multi-organ failure (MOF) is fatal and associated with high mortality (Coppell et al. 2010). The economic burden of VOD in ALL patients has not been reported in the published literature.ObjectiveTo investigate the incidence, inpatient mortality and economic burden of VOD among adult B-cell ALL patients in the US.MethodsThis was a retrospective cohort study using Truven Health MarketScan® Commercial and Medicare Supplemental Databases. We first identified the adult B-cell ALL patients. Patients with ≥1 inpatient claims or ≥2 non-diagnostic outpatient claims at least 30 days apart for any ALL diagnosis (ICD-9-CM 204.00-204.02, ICD-10-CM C91.00-C91.02) during 4/1/2009 - 10/31/2016 were extracted. All patients were required to have ≥1 hospitalization with diagnosis-related group in 834-839 on or after the first ALL diagnosis, be ≥18 years old, and have ≥6 months of continuous enrollment prior to the first ALL diagnosis date. Patients with medications for T-Cell ALL during the study period were excluded. VOD patients were then identified based on clinical criteria (Coppell et al. 2010) and expert opinions. VOD patients must have one of the following: 1) a ICD-10-CM code specifically for VOD diagnosis (K76.5), 2) prescription for defibrotide sodium that is indicated for treatment of VOD in the US, 3) at least two VOD symptoms from either Baltimore or Seattle criteria for VOD (ascites, abnormal weight gain, hyperbilirubinemia, or hepatomegaly) within 60 days post HSCT admission, or 4) multi-organ failure (MOF) with liver failure within 60 days post HSCT admission. The VOD index date was the first observed VOD diagnosis date, defibrotide sodium prescription date, or HSCT admission date. HSCT patients were excluded if they had evidence of chronic graft-versus-host disease (GVHD) any time before or 100 days after the VOD index date or if they had acute GVHD or total parenteral nutrition cholestasis during 60 days before or 100 days after the VOD index date. Severe VOD patients were defined as VOD patients with MOF. Patients were followed until the earliest of inpatient death, end of continuous enrollment, end of the study period (10/31/2016), and capped at 100 days. Outcomes included incidence rates of VOD in ALL patients, inpatient mortality of the VOD patients, and VOD-related costs and hospital length of stay during the 100 days post-index period. Costs were sum of the plan paid amount and out-of-pocket amount in 2016 US dollars. Descriptive analyses were conducted for all VOD patients, severe VOD patients and non-severe VOD patients, respectively.ResultsA total of 2,571 ALL patients were identified and 3.4% of them had VOD. Severe VOD patients accounted for 52% of the VOD patients. All VOD patients had HSCT before the VOD event. VOD patients were younger (mean age: 44.2 vs. 50.1), more likely to be male (male: 62.5% vs 55.0%) but sicker (mean Charlson comorbidity index: 2.1 vs. 1.9) compared with the average ALL patients. Inpatient mortality was higher among severe VOD patients (37.0%) when compared to both non-severe VOD (14.3%) and average VOD patients (26.1%). Mean (SD) VOD-related costs were $55,975 ($160,335) for All VOD patients, $86,953 ($206,906) for severe VOD patients and $22,047 ($72,847) for non-severe VOD patients (Figure 1). Mean (SD) VOD-related length of stay was 39.3 (33.0) days among all VOD patients, 49.2 (36.8) days for severe VOD patients and 28.5 (24.3) days for non-severe VOD patients.ConclusionsThe incidence of VOD is low in adult B-cell ALL patients. The diagnosis of VOD is clinical and as such might be underdiagnosed within the current study. Approximately half of the VOD events among ALL patients are severe involving MOFs. VOD events are associated with considerable economic burden and high inpatient mortality, with greater economic burden and inpatient mortality rate among severe VOD patients. These results may potentially underestimate the burden of VOD in ALL patients due to the fact that the HCPCS code specific for defibrotide sodium was not available given its recent approval in the US (2016). Future studies with more recent data are needed to accurately quantify the economic burden of VOD in the US. [Display omitted] DisclosuresZhang:Amgen Inc.: Employment, Equity Ownership. Romanov:Amgen, Inc.: Employment, Equity Ownership. Cong:Amgen Inc.: Employment, Equity Ownership.

Economic Burden of Hematopoietic Stem Cell Transplantation (HSCT) in Patients with Acute Lymphoblastic Leukemia (ALL) in the US

IntroductionAcute lymphoblastic leukemia (ALL) is a rare disease that affects lymphoblasts derived from lymphoid stem cells and due to the acute nature of this cancer, it is rapidly fatal without treatment (National Cancer Institute, 2016). The average 5-year overall survival (OS) rate was 35% for adult ALL and over 90% of the relapsed or refractory patients eventually die with a median OS of 3-6 months (Kantarjian HM et al. 2010, Bassan and Hoelzer 2011, Forman and Rowe 2013). Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative option for patients with B-cell ALL. Previous studies find that HSCT is associated with high costs and healthcare resource use. However, there is no study examining the allogeneic HSCT costs specifically for the adult ALL patients.ObjectiveThe aim of this study is to quantify the economic burden of allogeneic HSCT for adult B-cell ALL patients and relapsed adult B-cell ALL patients in the US.MethodsThis was a retrospective cohort study using Truven Health MarketScan® Commercial and Medicare Supplemental Databases. Patients with ≥1 inpatient claims or ≥2 non-diagnostic outpatient claims at least 30 days apart for any ALL diagnosis (ICD-9-CM 204.00-204.02, ICD-10-CM C91.00-C91.02) during 4/1/2009 - 10/31/2016 were extracted. All patients were required to have ≥1 hospitalization with diagnosis-related group in 834-839 on or after the first ALL diagnosis, have ≥1 allogeneic HSCT hospitalization (index date is the admission date for the initial HSCT hospitalization), are ≥18 years old on index date, and have ≥6 months of continuous enrollment prior to index date. Patients with medications for T-Cell ALL during the study period were excluded. Relapsed ALL patients were required to have ≥1 inpatient claims or ≥2 non-diagnostic outpatient claims at least 30 days apart for relapsed ALL diagnosis (ICD9: 204.02, ICD10: C91.02). Patients were followed until the earliest of inpatient death, end of continuous enrollment, or end of the study period (10/31/2016). Outcomes included all-cause and HSCT-related costs and total hospital length of stay (LOS) observed during the index hospitalization, and during 100, 180, or 365 days post-index periods (for the subset of patients with at least 100, 180, or 365 days of continuous enrollment after index date or an inpatient death during that follow-up). The costs for the HSCT-related complications such as graft versus host disease (both acute and chronic), hepatic veno-occlusive disease (VOD), graft failure, serious infections, bronchiolitis obliterans, secondary malignancies, and inpatient death were included, as well as the costs for transplant conditioning regimens during the 14 days before HSCT. Costs were sum of the plan paid amount and out-of-pocket amount in 2016 dollars. All descriptive analyses were conducted for patients with ALL (including both frontline and relapsed ALL) and relapsed ALL, separately.ResultsA total of 692 ALL patients (mean age: 45.6; male: 56.1%; mean Charlson comorbidity index: 3.2) were identified. Among all the ALL patients, 123 had relapsed ALL. Among ALL patients, mean (SD; median) costs were $275,642 ($316,109; $212,742) and mean (SD) LOS was 31.1 (20.9) days during the initial HSCT hospitalization (Table 1). During the first year post index, mean (SD; median) all-cause and HSCT-related costs were $543,146 ($416,148; $455,245) and $394,069 ($378,893; $301,977), respectively, with all-cause and HSCT-related mean (SD) LOS of 52.5 (41.5) and 49.2 (40.3) days. Among relapsed ALL patients, mean (SD; median) costs were $319,643 ($310,479; $255,545) during the initial HSCT hospitalization (Table 2). Mean (SD; median) all-cause and HSCT-related costs were $680,503 ($651,399; $556,244) and $535,245 ($577,152; $395,031) during the first year post index. Mean (SD) LOS was 33.9 (18.0) days during the initial HSCT hospitalization and 61.5 (46.4) and 59.1 (45.8) days during the first year post index for all-cause and HSCT-related hospital stays, respectively. The initial HSCT hospitalization accounts for about 47% and 51% of the total costs in the first year after HSCT for ALL and relapsed ALL patients, respectively.ConclusionsAllogeneic HSCT in ALL is associated with substantial economic burden, especially among relapsed ALL patients. During the first year post HSCT, about half of the total costs occurred during the initial HSCT hospitalization. [Display omitted] DisclosuresZhang:Amgen Inc.: Employment, Equity Ownership. Cong:Amgen Inc.: Employment, Equity Ownership.

An Artificial Intelligence Approach for B Lymphoblastic Leukemia Minimal Residual Disease Detection and Clinical Prognosis Prediction Using Flow Cytometry Data

IntroductionDetection of minimal residual disease (MRD) of B-cell acute lymphoblastic leukemia (B-ALL) measured by flow cytometry (FC) has been shown to be an important prognostic indicator in B-ALL. However, the current analysis is based on the manual gating by the reviewers; therefore, objectivity could be compromised, and decentralization of the B-ALL MRD detection is difficult to be established. We then aimed to develop an objective diagnostic tool via artificial intelligence (AI) technique for FC data interpretation in order to provide efficient and objective B-ALL MRD detection.MethodsRetrospective FC data of patients with adult B-ALL from 2009 to 2016 in National Taiwan University Hospital were enrolled. A total of 1,073 unique bone marrow FC samples were collected for analysis. Each of the samples had a 10-tube test done on 100,000 cells - each cell was measured in 6 fluorescent channels (FSC, SSC, FITC, PE, PerCP, APC) within one tube.The flow conclusion of each FC sample was categorized into “positive MRD” and “no MRD” groups according to previous manual interpretation, and the whole dataset was randomly divided into 3 groups: Training set (n=718), Accuracy set (n=141) and Validation set (n=178). The Training set was used to train the algorithm, and the Accuracy set was used to evaluate the accuracies achieved and optimize algorithmic parameters. The final optimized algorithm was then evaluated blindly in Validation set, with the concordance rate comparing the manual and the AI conclusions in distinguishing “positive MRD” from “no MRD”.For the algorithm development, the recorded numerical values of the 6 fluorescent channels (FSC, SSC, FITC, PE, PerCP, APC) of each tube (100,000 cells) were considered as raw feature attributes. The probabilistic distributions of these attributes were first modeled as multivariate Gaussian mixture model using a sub-dictionary learning approach. Then a probabilistic derivation was exploited to compute per-sample L2-normalized vectorized representations. Lastly, representations of each tube were then concatenated to be the final feature input to the supervised machine learning classifier, in this case, a support vector machine with linear kernel. In addition, ANOVA-based feature selection was also conducted throughout the experiments.For outcome correlation analysis, we included 35 adult B-ALL patients with available FC data after induction therapy, record their clinical parameters and measured their overall survival (OS) and progression-free survival (PFS), with median follow-up 40.0 months. The Kaplan-Meier curves were constructed to estimated OS and RFS.ResultsThe primary algorithm concordance estimated using the Accuracy set was 90.8% and the area under the receiver operating characteristic curve (AUC) is 0.944 (Table1). The calibrated algorithm, adjusted with training in Accuracy set, can produce a concordance rate of 88.2% with manual interpretation on Validation set, and the AUC is 0.919 (Table 1).It is noteworthy that it only took 7 seconds to analyze one FC sample using the AI algorithm while it took approximately 15 to 30 minutes for manual gating by trained professionals. Furthermore, the concordance of the algorithm developed from 10 tube-data remained almost unchanged when the tube number decreased. In fact, algorithm from 1 tube still yields an AUC of 0.874 (vs. 0.919 from 12 tubes), indicating that AI algorithm may reduce laboratory testing currently applied in standard FC processing.For outcome correlation, B-ALL patients with no MRD by AI algorithm had significant longer OS compared to those with positive MRD (NR vs 20.0 months, p=0.0051). Moreover, patients with no MRD also had significant longer RFS compared to those with positive MRD (8.9 vs 5.2 months, p=0.019), (Figure.1).ConclusionsThis is the first study using AI approach to develop FC data diagnostic algorithms with prognosis implications for B-ALL, demonstrating the advantages of reliability, high efficacy and time saving. Incorporating other test results into AI algorithm may lead to more precise prognostic prediction in the future and potentially guide therapeutic strategy for B-ALL. [Display omitted] DisclosuresKo:Celgene International Sàrl: Research Funding. Li:Celgene International Sàrl: Research Funding. Tien:Celgene International Sàrl: Research Funding. Tang:Celgene International Sàrl: Research Funding.

Interventions and outcomes of adult patients with B-ALL progressing after CD19 chimeric antigen receptor T-cell therapy

AbstractCD19-targeted chimeric antigen receptor (CAR) T-cell therapy has become a breakthrough treatment of patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, despite the high initial response rate, the majority of adult patients with B-ALL progress after CD19 CAR T-cell therapy. Data on the natural history, management, and outcome of adult B-ALL progressing after CD19 CAR T cells have not been described in detail. Herein, we report comprehensive data of 38 adult patients with B-ALL who progressed after CD19 CAR T therapy at our institution. The median time to progression after CAR T-cell therapy was 5.5 months. Median survival after post–CAR T progression was 7.5 months. A high disease burden at the time of CAR T-cell infusion was significantly associated with risk of post–CAR T progression. Thirty patients (79%) received salvage treatment of post–CAR T disease progression, and 13 patients (43%) achieved complete remission (CR), but remission duration was short. Notably, 7 (58.3%) of 12 patients achieved CR after blinatumomab and/or inotuzumab administered following post–CAR T failure. Multivariate analysis revealed that a longer remission duration from CAR T cells was associated with superior survival after progression following CAR T-cell therapy. In summary, overall prognosis of adult B-ALL patients progressing after CD19 CAR T cells was poor, although a subset of patients achieved sustained remissions to salvage treatments, including blinatumomab, inotuzumab, and reinfusion of CAR T cells. Novel therapeutic strategies are needed to reduce risk of progression after CAR T-cell therapy and improve outcomes of these patients.

PD-1 Inhibition Enhances Blinatumomab Response in a UCB/PDX Model of Relapsed Pediatric B-Cell Acute Lymphoblastic Leukemia.

Immune therapies such as blinatumomab, CD19-directed bispecific CD3 T-cell Engager (BiTE), have resulted in significant improvements in outcomes for relapsed B-cell acute lymphoblastic leukemia (B-ALL). However, up to half of blinatumomab treated patients do not respond completely or relapse after therapy. As a result, there is a need to identify potential strategies to improve the efficacy of BiTE therapy. The anti-PD-1 antibody pembrolizumab has been shown to successfully activate T cells against a wide range of cancer types. Here, we tested the ability of umbilical cord blood (UCB) reconstituted mice to respond to blinatumomab therapy with or without concurrent pembrolizumab treatment. Humanized mice were engrafted with patient-derived xenograft (PDX) cells derived from pediatric and adolescent/young adult (AYA) B-ALL patients who had either failed to achieve remission with negative minimum residual disease (MRD negative) or experienced a relapse. Mock-treated humanized mice engrafted with PDX cells efficiently developed overt disease within 30 days of engraftment of B-ALL. However, single agent therapy with either blinatumomab or pembrolizumab reduced disease burden in engrafted mice, with some mice observed to be MRD negative after the 28-day treatment course. Combination therapy significantly improved the percentage of MRD negative mice and improved long-term survival and cure rates as compared to mice that were given blinatumomab alone. Importantly, no benefits were observed in treated mice that lacked human immune cell reconstitution. These results indicate that UCB-humanized NRGS mice develop activatable immune function, and UCB-humanized PDX leukemia models can be used in preclinical studies to evaluate specificity, efficacy, and cooperativity of immune therapies in B-ALL.

Consensus Recommendations for MRD Testing in Adult B-Cell Acute Lymphoblastic Leukemia in Ontario.

Measurable (minimal) residual disease (MRD) is an established, key prognostic factor in adult B-cell acute lymphoblastic leukemia (B-ALL), and testing for MRD is known to be an important tool to help guide treatment decisions. The clinical value of MRD testing depends on the accuracy and reliability of results. Currently, there are no Canadian provincial or national guidelines for MRD testing in adult B-ALL, and consistent with the absence of such guidelines, there is no uniform Ontario MRD testing consensus. Moreover, there is great variability in Ontario in MRD testing with respect to where, when, and by which technique, MRD testing is performed, as well as in how the results are interpreted. To address these deficiencies, an expert multidisciplinary working group was convened to define consensus recommendations for improving the provision of such testing. The expert panel recommends that MRD testing should be implemented in a centralized manner to ensure expertise and accuracy in testing for this low volume indication, thereby to provide accurate, reliable results to clinicians and patients. All adult patients with B-ALL should receive MRD testing after induction chemotherapy. Philadelphia chromosome (Ph)-positive patients should have ongoing monitoring of MRD during treatment and thereafter, while samples from Ph-negative B-ALL patients should be tested at least once later during treatment, ideally at 12 to 16 weeks after treatment initiation. In Ph-negative adult B-ALL patients, standardized, ideally centralized, protocols must be used for MRD testing, including both flow cytometry and immunoglobulin (Ig) heavy chain and T-cell receptor (TCR) gene rearrangement analysis. For Ph-positive B-ALL patients, MRD testing using a standardized protocol for reverse transcription real-time quantitative PCR (RT-qPCR) for the BCR-ABL1 gene fusion transcript is recommended, with Ig/TCR gene rearrangement analysis done in parallel likely providing additional clinical information.

Chimeric Antigen Receptor T-Cell Therapy for B-Cell Acute Lymphoblastic Leukemia: Current Landscape in 2021.

Immunotherapy with T cells engineered to express a chimeric antigen receptor (CAR T cells) is reshaping the management of patients with relapsed or refractory B-cell malignancies. High efficacy of CD19-targeted CAR T cells has been reported in children and adults with B-cell acute lymphoblastic leukemia (B-ALL), with complete responses without detectable minimal residual disease occurring in approximately 80% to 90% of patients. This led to the approval of tisagenlecleucel (Kymriah) by the Food and Drug Administration based on the results of the ELIANA trial. Although CD19 CAR T-cell therapy may be curative in children, responses are short-lived in most adult B-ALL patients. In addition, CAR T-cell therapy can be associated with severe, potentially life-threatening, toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. Here, we review the recent advances in CAR T-cell therapy for R/R B-ALL and discuss strategies to improve its efficacy while minimizing toxicities.

NMR-based plasma metabolomics of adult B-cell acute lymphoblastic leukemia.

Acute lymphoblastic leukemia (ALL) is one of the common malignant tumors. Compared with childhood ALL, the treatment effect of adult B-cell ALL is less effective and remains a big challenge. In order to explore the pathogenesis of adult B-cell ALL and find new diagnostic biomarkers to develop sensitive diagnostic tools, we investigated the plasma metabolites of adult B-cell ALL by using 1H NMR (nuclear magnetic resonance) metabolomics. Relative to healthy controls, adult B-cell ALL patients showed abnormal metabolism, including glycolysis, gluconeogenesis, amino acid metabolism, fatty acid metabolism and choline phospholipid metabolism. What's more important, we also found that the optimal combination of choline, tyrosine and unsaturated lipids has the potential to diagnose and prognose adult B-cell ALL in the clinic.

Donor-Derived CAR T Cells Engineered with Sleeping Beauty Achieve Anti-Leukemic Activity without Severe Toxicity

Donor-Derived CAR T Cells Engineered with Sleeping Beauty Achieve Anti-Leukemic Activity without Severe Toxicity

Clinical Impact of CD25/CD123 Coexpression in Adult B-Cell Acute Lymphoblastic Leukemia Patients.

This study aimed to determine the clinical impact of CD25+/CD123+ coexpression in adult B-cell acute lymphoblastic leukemia (B-ALL) cases. One hundred and twenty newly diagnosed B-ALL patients (≤60 years old) were included in this study. CD123 and CD25 expression on leukemic blast cells were assessed using flow cytometry. CD25+/CD123+ coexpression was detected in 40/120 B-ALL patients (33.3%). All B-ALL patients showed CD25+/CD123+ coexpression had lower induction of remission response and shorter overall survival as compared to B-ALL cases lacking coexpression. In conclusion, CD25+/CD123+ positive coexpression is a reliable flow cytometry marker for prediction of the outcome of adult B-ALL patients and could be used as a novel parameter for risk stratification of adult B-ALL cases.

Ikaros Family Zinc Finger 1 Mutation Is an Adverse Prognostic Factor for Patients with Adult B-Cell Acute Lymphoblastic Leukemia

To investigate the prognosis of patients with adult B-cell acute lymphoblastic leukemia (B-ALL) accompanied with Ikaros family zinc finger 1 (IKZF1) mutation, and to explore the role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in improving the clinical outcome of patients. The clinical data of 164 adult B-ALL patients who received IKZF-1 mutation detection by capillary electrophoresis of bone marrow were collected, and the relationship between the IKZF-1 gene mutation and the prognosis of adult B-ALL patients was analyzed. Among 164 adult B-ALL patients, the patients with IKZF-1 mutation (IKZF-1+) were 80 cases, while the patients without IKZF-1 mutation (IKZF-1-) were 84 cases. Among 80 IKZF-1 positive patients, according to the treatment method after complete remission these patients were divided into HSCT group (48 cases) and chemotherapy group (32 cases). Analysis showed that the 3-year overall survival (OS) and leukemia-free survival (LFS) rates in the IKZF1+ group were much lower. The OS and LFS rate in transplantation group were 50.3%±8.3%, 41.6%±8.5%; the OS and LFS rates in the chemotherapy group were 33.7%±12.8%, 31.5%±9.5%, which were lower than those in the IKZF1- group (the transplantation group: 79.5%±7.6%, 64.0%±8.4%; the chemotherapy group: 54.4%±9.9%, 40.6%±9.6% respectirely (P＜0.05). Among 80 B-ALL patients with IKZF-1- mutation, the 3-year OS and LFS rates were significantly higher in the transplantation group (55.3%±7.5%, 48.3%±7.6%) than those in the chemotherapy group (32.9%±11.8%, 28.4%±10.3%) with IKZF1 mutation (P＜0.05). IKZF1 mutation is an adverse prognostic factor for adult B-ALL patients, However, allo-HSCT significantly improves the OS and LFS of patients and also their clinical outcomes.

Induction of NK Cell Reactivity against B-Cell Acute Lymphoblastic Leukemia by an Fc-Optimized FLT3 Antibody.

Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism by which antitumor antibodies mediate therapeutic efficacy. At present, we evaluate an Fc-optimized (amino acid substitutions S239D/I332E) FLT3 antibody termed 4G8-SDIEM (FLYSYN) in patients with acute myeloid leukemia (NCT02789254). Here we studied the possibility to induce NK cell ADCC against B-cell acute lymphoblastic leukemia (B-ALL) by Fc-optimized FLT3 antibody treatment. Flow cytometric analysis confirmed that FLT3 is widely expressed on B-ALL cell lines and leukemic cells of B-ALL patients. FLT3 expression did not correlate with that of CD20, which is targeted by Rituximab, a therapeutic monoclonal antibody (mAb) employed in B-ALL treatment regimens. Our FLT3 mAb with enhanced affinity to the Fc receptor CD16a termed 4G8-SDIE potently induced NK cell reactivity against FLT3-transfectants, the B-ALL cell line SEM and primary leukemic cells of adult B-ALL patients in a target-antigen dependent manner as revealed by analyses of NK cell activation and degranulation. This was mirrored by potent 4G8-SDIE mediated NK cell ADCC in experiments with FLT3-transfectants, the cell line SEM and primary cells as target cells. Taken together, the findings presented in this study provide evidence that 4G8-SDIE may be a promising agent for the treatment of B-ALL, particularly in CD20-negative cases.