Refractory B-cell Acute Lymphoblastic Leukemia Research Articles

Tisagenlecleucel therapy for relapsed or refractory B-cell acute lymphoblastic leukaemia in infants and children younger than 3 years of age at screening: an international, multicentre, retrospective cohort study

Children aged younger than 3 years were excluded from the ELIANA phase 2 trial of tisagenlecleucel in children with acute lymphoblastic leukaemia. The feasibility, safety, and activity of tisagenlecleucel have not been defined in this group, the majority of whom have high-risk (KMT2A-rearranged) infant acute lymphoblastic leukaemia and historically poor outcomes despite intensification of chemotherapy, and for whom novel therapies are urgently needed. We aimed to provide real-world outcome analysis of the feasibility, activity, and safety of tisagenlecleucel in younger children and infants with acute lymphoblastic leukaemia. We did an international, multicentre, retrospective cohort study at 15 hospitals across ten countries in Europe. Eligible patients were children aged younger than 3 years at screening between Sept 1, 2018, and Sept 1, 2021, who were screened for tisagenlecleucel therapy for relapsed or refractory B-cell precursor acute lymphoblastic leukaemia according to licensed indications. Patients received a single intravenous infusion of tisagenlecleucel. We tracked chimeric antigen receptor T-cell therapy outcomes using a standardised data reporting form. Overall survival, event-free survival, stringent event-free survival, B-cell aplasia, and toxicity were assessed in all patients who received a tisagenlecleucel infusion. 38 eligible patients were screened, of whom 35 (92%) received a tisagenlecleucel infusion. 29 (76%) of 38 patients had KMT2A-rearranged acute lymphoblastic leukaemia, and 25 (66%) had relapsed after previous allogeneic haematopoietic stem-cell transplantation (HSCT). Patients had previously received a median of 2 lines (IQR 2-3) of (non-HSCT) therapy. Seven (18%) of 38 patients had received inotuzumab and 14 (37%) had received blinatumomab. After a median of 14 months (IQR 9-21) of follow-up, overall survival at 12 months after tisagenlecleucel infusion was 84% (64-93; five patients had died), event-free survival was 69% (47-83; nine events), and stringent event-free survival was 41% (23-58; 18 events). The probability of ongoing B-cell aplasia was 70% (95% CI 46-84; seven events) at 12 months. Adverse events included cytokine release syndrome, which occurred at any grade in 21 (60%) of 35 patients and at grade 3 or worse in five (14%), and neurotoxicity at any grade in nine (26%), none of which were severe. Measurable residual disease-negative complete response with or without haematological recovery occurred in 24 (86%) of 28 patients who had measurable disease. These data suggest that tisagenlecleucel has antitumour activity and has an acceptable safety profile for young children and infants with B-cell precursor acute lymphoblastic leukaemia. None.

Novel Treatments for Pediatric Relapsed or Refractory Acute B-Cell Lineage Lymphoblastic Leukemia: Precision Medicine Era.

With the markedly increased cure rate for children with newly diagnosed pediatric B-cell acute lymphoblastic leukemia (B-ALL), relapse and refractory B-ALL (R/R B-ALL) remain the primary cause of death worldwide due to the limitations of multidrug chemotherapy. As we now have a more profound understanding of R/R ALL, including the mechanism of recurrence and drug resistance, prognostic indicators, genotypic changes and so on, we can use newly emerging technologies to identify operational molecular targets and find sensitive drugs for individualized treatment. In addition, more promising and innovative immunotherapies and molecular targeted drugs that are expected to kill leukemic cells more effectively while maintaining low toxicity to achieve minimal residual disease (MRD) negativity and better bridge hematopoietic stem cell transplantation (HSCT) have also been widely developed. To date, the prognosis of pediatric patients with R/R B-ALL has been enhanced markedly thanks to the development of novel drugs. This article reviews the new advancements of several promising strategies for pediatric R/R B-ALL.

P1464: DECREASING HPK1 EXPRESSION IN CD19 CAR-T CELLS: A NOVEL STRATEGY TO OVERCOME CHALLENGES OF CELL THERAPY FOR ADULT (R/R) B-ALL

Background: Since the FDA approved the first CD19 directed chimeric antigen receptor (CAR) T-cell therapy (Kymriah) for pediatric and young adult patients with relapsed or refractory (r/r) B-cell acute lymphoblastic leukemia (ALL), cytokine release syndrome (CRS) has still been a life-threatening toxicity that limits the full therapeutic potential in adults [1,2]. So far, Tecartus was the first and only approved CAR-T-cell therapy for adult (r/r) B-ALL, which was based on results from ZUMA-3 study. CRS occurred in 92% patients, and neurologic toxicities occurred in 87% patients in ZUMA-3 study[3], suggesting that therapeutic developments are needed to ensure more safe and potent options for adult B-ALL. Aims: Our preclinical data demonstrated that CAR-T cells with decreased HPK1 expression had significantly enhanced antitumor effects and did not induce higher grade CRS [4]. Thus, the first-in-human clinical study is ongoing, to test CD19 CAR-T cells with decreased HPK1 expression (XYF19 CAR-T cells) for adult (r/r) B-ALL (NCT04037566). Methods: Dose-escalation study was initiated to explore the safety and efficacy of XYF19 CAR-T cells in adult (r/r) B-ALL. 11 eligible adult (r/r) B-ALL patients with a median age of 37 years (range 19 - 61 years) were enrolled. The cell dosage of XYF19 was significantly lower than Tecartus and Kymriah, participants were infused with XYF19 CAR-T cells: 3 at low dose (2.0×105/kg), 5 at medium dose (5.0×105/kg), and 3 at high dose (1.0×106/kg). All patients received a conditioning regimen of IV fludarabine (30mg/m2/d) for 4 days and cyclophosphamide (500mg/m2/d) for 2 days. Results: 30 days after infusion with XYF19 CAR-T cells, 8 of the 11 (72.7%) patients had achieved complete remission (CR) or CR with incomplete count recovery (CRi). Considering the low dosage of XYF19 and that the CR/CRi rate is 71% with Tecartus [2] and 69% with Kymriah [3], the clinical response of XYF19 is similar or even the highest in these three studies. Strikingly, in this clinical trial, no patient developed neurotoxicity and none has yet experienced dose-limiting toxicity. No grade 3 or higher CRS occurred in XYF19 treated patients, while Grade 3 or higher CRS was observed in 26% of patients with Tecartus [2], and 72% of patients with Kymriah[3]. No neurologic events occurred in the current study, while the incidence of neurological events was 51% with Tecartus [2] and 43% with Kymriah[3]. Thus, XYF19 is a strong potential novel treatment for CD19 CAR-T cell therapy in adult B-ALL. Summary/Conclusion: Treatment with XYF19 CAR-T cells promises a novel treatment that can alleviate some of the stern challenges of CD19 CAR-T cell therapy for adult patients with r/r B-ALL. In the current study, this treatment showed robust activity against adult (r/r) B-ALL without >Grade 2 toxicity. This efficacy and safety will be demonstrated in further trials with larger sample sizes.

Overcoming resistance to anti-CD19 CAR T-cell therapy in B-cell malignancies.

Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy has rapidly changed current treatment pattern, providing a better option for individuals with primary refractory or relapsed B-cell non-Hodgkin lymphoma (r/r B-NHL) and B-cell acute lymphoblastic leukemia (r/r B-ALL). However, despite the outstanding efficacy, a high relapse rate is still found in some B-cell malignancies after anti-CD19 CAR T-cell therapy, which emerges as a main barrier for improving the overall response and long-term outcomes. Understanding the resistance mechanism is crucial to improve current CAR T products, better incorporate them into the current therapy system and develop novel CAR approaches. Herein, we discuss the latest advances in understanding the mechanisms limiting efficacy of CAR T-cell therapy, resulting in CD19 negative (CD19- ) and CD19 positive (CD19+ ) relapses. We also provide a whole scenario of current potential strategies to overcome these barriers.

Decreasing HPK1 expression in CD19 CAR-T cells: A novel strategy to overcome challenges of cell therapy for adult (r/r) B-ALL.

7041 Background: Since the FDA approved the first CD19 CAR T cell therapy (Kymriah) for pediatric and young adult patients with relapsed or refractory (r/r) B-cell acute lymphoblastic leukemia (ALL), cytokine release syndrome (CRS) has still been a life-threatening toxicity that limits the full therapeutic potential in adults [1,2]. So far, Tecartus was the first and only approved CAR-T cell therapy for adult r/r B ALL, which was based on results from ZUMA-3 study. CRS occurred in 92% patients, and neurologic toxicities occurred in 87% patients in ZUMA-3 study[3], suggesting that therapeutic developments are needed to ensure more safe options for adult B-ALL. Our preclinical data demonstrated that CAR-T cells with decreased HPK1 expression had enhanced antitumor effects and did not induce higher grade CRS [4]. Thus, the first-in-human clinical study is ongoing to test CD19 CAR-T cells with decreased HPK1 expression (XYF19 CAR-T cells) for adult (r/r) B-ALL (NCT04037566). Methods: Dose-escalation study was initiated to explore the safety and efficacy of XYF19 CAR-T cells in adult r/r B-ALL. 11 eligible adult r/r B-ALL patients were enrolled. The cell dosage of XYF19 was significantly lower than Tecartus and Kymriah, participants were infused with XYF19 CAR-T cells: 3 at low dose (2.0×105/kg), 5 at medium dose (5.0×105/kg), and 3 at high dose (1.0×106/kg). All patients received a conditioning regimen of IV fludarabine (30mg/m2/d) for 4 days and cyclophosphamide (500mg/m2/d) for 2 days. Results: 30 days after infusion with XYF19 CAR-T cells, 8 of the 11 (72.7%) patients had achieved complete remission (CR) or CR with incomplete count recovery (CRi). Considering the low dosage of XYF19 and that the CR/CRi rate is 71% with Tecartus [2] and 69% with Kymriah [3], the clinical response of XYF19 is similar or even the highest in these three studies. Strikingly, in this clinical trial, no patient has yet experienced dose-limiting toxicity. No grade 3 or higher CRS occurred in XYF19 treated patients, while Grade 3 or higher CRS was observed in 26% of patients with Tecartus [2], and 72% of patients with Kymriah[3]. No neurologic events occurred in the current study, while the incidence of neurological events was 51% with Tecartus [2] and 43% with Kymriah[3]. Thus, XYF19 is a strong potential novel treatment for CD19 CAR-T cell therapy in adult B-ALL. Conclusions: Treatment with XYF19 CAR-T cells promises a novel treatment that can alleviate some of the stern challenges of CD19 CAR-T cell therapy for adult patients with r/r B-ALL. In the current study, this treatment showed robust activity against adult (r/r) B-ALL without > Grade 2 toxicity. This efficacy and safety will be demonstrated in further trials with larger sample sizes.

Outcomes of Hispanic and non-Hispanic white pediatric and young adult patients with B-cell acute lymphoblastic leukemia after commercial tisagenlecleucel.

10016 Background: Population-level data show significantly inferior outcomes for Hispanic children, adolescents, and young adults (CAYA) diagnosed with B-cell acute lymphoblastic leukemia (B-ALL) relative to non-Hispanic whites (NHW). Here, we compare outcomes between Hispanic and NHW CAYA patients with relapsed and/or refractory (RR) B-ALL receiving tisagenlecleucel, a CD19-specific chimeric antigen receptor (CAR) T cell therapy. Methods: We used data from the Pediatric Real World CAR Consortium retrospective cohort of 200 patients who underwent cell shipment for standard-of-care tisagenlecleucel between August 2017 and March 2020 (N=15 US institutions). Race/ethnicity was identified by medical record review. Patients reported as belonging to more than one racial/ethnic group were classified as multiracial and excluded from analysis. Baseline factors, outcomes, and safety post-infusion were characterized for Hispanic vs. NHW infused patients. Outcomes included complete response (CR) rate, overall survival (OS), duration of response (DOR), and duration of B-cell aplasia (DBA). A multivariate Cox model for OS was constructed, including all baseline factors. Results: Among 185 infused patients, 90 (48.6%) were NHW and 70 (37.8%) were Hispanic. Among 15 non-infused patients, 3 (20.0%) were NHW and 5 (33.3%) were Hispanic. Hispanic patients were significantly older at diagnosis (mean: 10.7 vs. 8.3 years, p=0.02) and had significantly shorter time from diagnosis to infusion (mean: 34.4 vs. 46.4 months, p=0.04). Hispanic and NHW patients did not significantly differ across sex, leukemia type, number of prior lines of therapy, receipt of prior CD19-directed therapy, level of disease burden pre-infusion, and number of relapses pre-infusion. Hispanic and NHW patients did not significantly differ across 1-month CR, 6-month OS, 1-year OS, 18-month OS, 6-month DOR, 1-year DOR, 6-month DBA, and 1-year DBA (Table). On multivariate analysis including the above covariates, OS did not significantly differ for Hispanic patients (HR=1.04, p=0.92). Hispanic and NHW patients did not significantly differ across grade ≥ 3 cytokine release syndrome, grade ≥ 3 neurotoxicity, grade 4 neutropenia, tumor lysis syndrome, or number of infections post-infusion. Conclusions: Outcomes were similar between Hispanic and NHW CAYA RR B-ALL patients receiving tisagenlecleucel in the real-world setting. Increasing access to CAR therapy among Hispanic CAYA B-ALL patients could help mitigate population-level disparities in outcomes observed after receipt of conventional therapies. [Table: see text]

TPEN selectively eliminates lymphoblastic B cells from bone marrow pediatric acute lymphoblastic leukemia patients.

B-cell acute lymphoblastic leukemia (B-ALL) is a hematologic disorder characterized by the abnormal proliferation and accumulation of immature B-lymphoblasts arrested at various stages of differentiation. Despite advances in treatment, a significant percentage of pediatric patients with precursor B-ALL still relapse. Therefore, alternative therapies are needed to improve the cure rates for pediatric patients. TPEN (N, N, N', N'-tetrakis(2-pyridylmethyl)-ethylenediamine) is a pro-oxidant agent capable of selectively inducing apoptosis in leukemia cell lines. Consequently, it has been suggested that TPEN could be a potential agent for oxidative therapy. However, it is not yet known whether TPEN can selectively destroy leukemia cells in a more disease-like model, for example, the bloodstream and bone marrow (BM), ex vivo. This investigation is an extension of a previous study that dealt with the effect of TPEN on ex vivo isolated/purified refractory B-ALL cells. Here, we evaluated the effect of TPEN on whole BM from nonleukemic patients (control) or pediatric patients diagnosed with de novo B-ALL or refractory B-ALL cells by analyzing the hematopoietic cell lineage marker CD34/CD19. Although TPEN was innocuous to nonleukemic BM (n = 3), we found that TPEN significantly induced apoptosis in de novo (n = 5) and refractory B-ALL (n = 6) leukemic cell populations. Moreover, TPEN significantly increased the counts of cells positive for the oxidation of the stress sensor protein DJ-1, a sign of the formation of H2O2, and significantly increased the counts of cells positive for the pro-apoptotic proteins TP53, PUMA, and CASPASE-3 (CASP-3), indicative of apoptosis, in B-ALL cells. We demonstrate that TPEN selectively eliminates B-ALL cells (CD34 + /CD19 +) but no other cell populations in BM (CD34 + /CD19-; CD34-/CD19 + ; CD34-/CD19-) independent of age, diagnosis status (de novo or refractory), sex, karyotype, or immunophenotype. Understanding TPEN-induced cell death in leukemia cells provides insight into more effective therapeutic oxidation-inducing anticancer agents.

Real-world use of tisagenlecleucel in infant acute lymphoblastic leukemia

AbstractInfants with B-cell acute lymphoblastic leukemia (B-ALL) have poor outcomes because of chemotherapy resistance leading to high relapse rates. Tisagenlecleucel, a CD19-directed chimeric antigen receptor T-cell (CART) therapy, is US Food and Drug Administration approved for relapsed or refractory B-ALL in patients ≤25 years; however, the safety and efficacy of this therapy in young patients is largely unknown because children <3 years of age were excluded from licensing studies. We retrospectively evaluated data from the Pediatric Real-World CAR Consortium to examine outcomes of patients with infant B-ALL who received tisagenlecleucel between 2017 and 2020 (n = 14). Sixty-four percent of patients (n = 9) achieved minimal residual disease-negative remission after CART and 50% of patients remain in remission at last follow-up. All patients with high disease burden at time of CART infusion (>M1 marrow) were refractory to this therapy (n = 5). Overall, tisagenlecleucel was tolerable in this population, with only 3 patients experiencing ≥grade 3 cytokine release syndrome. No neurotoxicity was reported. This is the largest report of tisagenlecleucel use in infant B-ALL and shows that this therapy is safe and can be effective in this population. Incorporating this novel immunotherapy into the treatment of infant B-ALL offers a promising therapy for a highly aggressive leukemia.

Approval of brexucabtagene autoleucel for adults with relapsed and refractory acute lymphocytic leukemia

AbstractIn October 2021, brexucabtagene autoleucel became the first anti-CD19 chimeric antigen receptor T-cell product to receive approval from the Food and Drug Administration to treat adults with relapsed and refractory B-cell acute lymphoblastic leukemia. The approval is based on results from the Zuma-3 trial and significantly widens treatment options for this patient population. In this article, we review outcomes from this study and its implications.

Cost-Effectiveness and Budget Impact Analyses of Tisagenlecleucel in Pediatric and Young Adult Patients with Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia from the Singapore Healthcare System Perspective.

PurposeChildren and young adults with relapsed or refractory (r/r) acute lymphoblastic leukemia (ALL) have poor survival due to ineffective therapy options. The newly approved chimeric antigen receptor T-cell (CAR-T) therapy, tisagenlecleucel, has demonstrated improved survival but at a high up-front cost. The study aims to evaluate the cost-effectiveness and budget impact of tisagenlecleucel versus salvage chemotherapy regimen (SCR) or blinatumomab (BLN) for the treatment of pediatric and young adult patients with relapsed/refractory B-cell ALL from the Singapore healthcare system perspective.Patients and MethodsA three-health state partitioned survival model was constructed to analyze the cost-effectiveness of tisagenlecleucel vs SCR/BLN with/without allogenic hematopoietic stem cell transplantation (allo-HSCT) over a lifetime period. Clinical efficacy for tisagenlecleucel, SCR and BLN were based on pooled data from ELIANA, ENSIGN and B2101J trials, the study by von Stackelberg et al 2011, and MT103-205 respectively. Medical costs from pre-treatment until terminal care, including treatment, side effects, follow-up, subsequent allo-HSCT and relapse, were considered. Incremental cost-effectiveness ratios (ICERs) were estimated as the incremental costs per quality-adjusted life-year (QALY) gain. Additionally, the financial impact of tisagenlecleucel introduction in Singapore was estimated, comparing the present treatment scenario (without tisagenlecleucel) with a future scenario (with tisagenlecleucel), over 5 years.ResultsIn the base-case analysis, tisagenlecleucel treatment demonstrated cost-effectiveness with an ICER of S$45,840 (US$34,762) per QALY (vs SCR) and S$51,978 (US$39,315) per QALY (vs BLN). The estimated budget ranges from S$477,857 (US$361,438) to S$1.4 million (US$1.05 million) annually for the initial 5 years.ConclusionTisagenlecleucel is likely to be a cost-effective treatment option with limited budget implications while treating r/r ALL patients who have failed at least 2 lines of prior therapies.

Preferential expansion of CD8+ CD19-CAR T cells postinfusion and the role of disease burden on outcome in pediatric B-ALL

AbstractT cells expressing CD19-specific chimeric antigen receptors (CD19-CARs) have potent antileukemia activity in pediatric and adult patients with relapsed and/or refractory B-cell acute lymphoblastic leukemia (B-ALL). However, not all patients achieve a complete response (CR), and a significant percentage relapse after CD19-CAR T-cell therapy due to T-cell intrinsic and/or extrinsic mechanisms. Thus, there is a need to evaluate new CD19-CAR T-cell products in patients to improve efficacy. We developed a phase 1/2 clinical study to evaluate an institutional autologous CD19-CAR T-cell product in pediatric patients with relapsed/refractory B-ALL. Here we report the outcome of the phase 1 study participants (n = 12). Treatment was well tolerated, with a low incidence of both cytokine release syndrome (any grade, n = 6) and neurotoxicity (any grade, n = 3). Nine out of 12 patients (75%) achieved a minimal residual disease-negative CR in the bone marrow (BM). High disease burden (≥40% morphologic blasts) before CAR T-cell infusion correlated with increased side effects and lower response rate, but not with CD19-CAR T-cell expansion. After infusion, CD8+ CAR T cells had a proliferative advantage over CD4+ CAR T cells and at peak expansion, had an effector memory phenotype with evidence of antigen-driven differentiation. Patients that proceeded to allogeneic hematopoietic cell transplantation (AlloHCT) had sustained, durable responses. In summary, the initial evaluation of our institutional CD19-CAR T-cell product demonstrates safety and efficacy while highlighting the impact of pre-infusion disease burden on outcomes. This trial was registered at www.clinicaltrials.gov as #NCT03573700.

Vibrio cholerae O1 (serovar inaba) as a cause of fatal bacteremia in a patient with relapsed acute lymphoblastic leukemia

O1 is an uncommon cause of bacteremia with only a few cases reported in published literature. We report a rare and fatal case and O1 serovar inaba bacteremia in a 29-year-old male patient on chemotherapy for relapsed and refractory B-cell acute lymphoblastic leukemia. He had no associated intestinal symptoms.

Identification of the Predictive Models for the Treatment Response of Refractory/Relapsed B-Cell ALL Patients Receiving CAR-T Therapy.

Background/AimsChimeric antigen receptor (CAR) T cells for refractory or relapsed (r/r) B-cell acute lymphoblastic leukemia (ALL) patients have shown promising clinical effectiveness. However, the factors impacting the clinical response of CAR-T therapy have not been fully elucidated. We here aimed to identify the independent factors of CAR-T treatment response and construct the models for predicting the complete remission (CR) and minimal residual disease (MRD)-negative CR in r/r B-ALL patients after CAR-T cell infusion.MethodsUnivariate and multivariate logistic regression analyses were conducted to identify the independent factors of CR and MRD-negative CR. The predictive models for the probability of remission were constructed based on the identified independent factors. Discrimination and calibration of the established models were assessed by receiver operating characteristic (ROC) curves and calibration plots, respectively. The predictive models were further integrated and validated in the internal series. Moreover, the prognostic value of the integration risk model was also confirmed.ResultsThe predictive model for CR was formulated by the number of white blood cells (WBC), central neural system (CNS) leukemia, TP53 mutation, bone marrow blasts, and CAR-T cell generation while the model for MRD-negative CR was formulated by disease status, bone marrow blasts, and infusion strategy. The ROC curves and calibration plots of the two models displayed great discrimination and calibration ability. Patients and infusions were divided into different risk groups according to the integration model. High-risk groups showed significant lower CR and MRD-negative CR rates in both the training and validation sets (p < 0.01). Furthermore, low-risk patients exhibited improved overall survival (OS) (log-rank p < 0.01), higher 6-month event-free survival (EFS) rate (p < 0.01), and lower relapse rate after the allogeneic hematopoietic stem cell transplantation (allo-HSCT) following CAR-T cell infusion (p = 0.06).ConclusionsWe have established predictive models for treatment response estimation of CAR-T therapy. Our models also provided new clinical insights for the accurate diagnosis and targeted treatment of r/r B-ALL.

Cytopenia after CAR-T Cell Therapy-A Brief Review of a Complex Problem.

Simple SummaryChimeric Antigen Receptor T-cell (CAR-T) immunotherapy has emerged as a new life-saving treatment modality in patients with relapsed or refractory B-cell malignancies and multiple-myeloma. In this form of therapy, patient’s T-cells are modified by various genetic techniques to express a new receptor that identifies and kills the cancer cells. With increasing use, they present with distinct immune mediated side effects such as cytokine release syndrome (CRS), neurotoxicity, and prolonged cytopenia. While our understanding of CRS and other immune side-effects has increased, prolonged cytopenia post CAR-T infusion remains under-recognized and under-reported. With the focus on prolonged cytopenia in this review, we aim to summarize findings of various clinical trials, postulated mechanisms, and clinical interventions to risk-stratify and manage this clinical entity.Chimeric Antigen Receptor T-cell (CAR-T) immunotherapy has emerged as an efficacious and life extending treatment modality with high response rates and durable remissions in patients with relapsed and refractory non-Hodgkin lymphoma (NHL), follicular lymphoma, and B-cell acute lymphoblastic leukemia (B-ALL) as well as in other diseases. Prolonged or recurrent cytopenias after CAR-T therapy have increasingly been reported at varying rates, and the pathogenesis of this complication is not yet well-understood but is likely contributed to by multiple factors. Current studies reported are primarily retrospective, heterogeneous in terms of CAR-Ts used and diseases treated, non-uniform in definitions of cytopenias and durations for end points, and vary in terms of recommended management. Prospective studies and correlative laboratory studies investigating the pathophysiology of prolonged cytopenias will enhance our understanding of this phenomenon. This review summarizes knowledge of these cytopenias to date.

Systematic review and pooled analysis of survival outcomes in patients with relapsed or refractory B-cell acute lymphoblastic leukaemia who have undergone haematopoietic stem cell transplant.

Information about the long-term survival impact of hematopoietic stem cell transplant (HSCT) in adults with relapsed/refractory B-cell acute lymphoblastic leukaemia is limited. The objective was to conduct a systematic review identifying studies reporting survival in HSCT-receiving patients and apply parametric analyses to predict long-term survival. Twenty-five relevant studies were identified. Analyses were conducted in 10 studies (n=503; "global" analysis) reporting overall survival (OS) data as Kaplan-Meier curves or at patient level. Four studies (n=217; "subgroup" analysis) measured OS from the point of HSCT. Patient-level data were recreated from Kaplan-Meier curves and pooled, with six models tested for longer-term extrapolation. Additionally, a sensitivity analysis was undertaken involving removal of data from the oldest study cohort (recruited between 1981-1997) to determine if the year which patients received HSCT impacted survival compared to post-2009 data. Median OS and five-year survival probability were 11.4 months and 24.4% (95% CI, 20.5-28.5%) in the global analysis, and 12.0 months and 28.4% (95% CI, 22.1-34.9%) in the subgroup analysis. The generalised gamma and Gompertz models fit longer-term extrapolation criteria. The generalised gamma model predicted survival at 10.4% vs. 14.8% (15 years), 8.3% vs. 12.8% (20 years), and 6.9% vs. 11.4% (25 years) for the global and subgroup analysis, respectively. The Gompertz model predicted survival to plateau at 23% vs. 25.6% just before 10 years. The sensitivity analysis excluding older data found median survival increased two-fold (25.3 vs. 12 months). Results synthesize long-term evidence of outcomes for HSCT-receiving patients, providing a basis for treatment comparison. Risk of death is low beyond four years and newer data appears correlated with improved outcomes.

Outcomes of relapsed B-cell acute lymphoblastic leukemia after sequential treatment with blinatumomab and inotuzumab

AbstractNovel monoclonal antibody (mAb)-based therapies targeting CD19 and CD22 (blinatumomab and inotuzumab) have shown high rates of complete remission (CR) and been used as a bridging treatment to potentially curative allogeneic hematopoietic stem cell transplantation (alloHSCT) in adults with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). However, limited data exist on the outcome of patients resistant to both mAbs as well as responses to each agent when progressed after the alternate antigen-targeted mAb. Herein, we report outcomes of 29 patients with R/R B-ALL previously treated with both blinatumomab and inotuzumab. Twenty-five patients (86.2%) received blinatumomab as first mAb (mAb1), and CD19-negative/dim relapses were observed in 44% of the patients. Inotuzumab induced CR in 68% of the patients for post-blinatumomab relapse regardless of CD19 expression status. The median time between mAb1 and mAb2 was 99 days. Twelve (63.2%) of 19 patients who achieved remission after mAb2 underwent alloHSCT. The median time from mAb2 to alloHSCT was 37.5 days. Acute graft-versus-host disease and nonrelapse mortality were observed in 58.3% (grade 3 or higher, 25%) and 41.7%, respectively. With a median follow-up of 16.8 months after mAb2, 19 patients (65.5%) relapsed, and 21 patients (72.4%) have died. Overall survival was not different between alloHSCT and non-alloHSCT patients. In conclusion, patients with B-ALL who relapsed after blinatumomab could be successfully rescued by inotuzumab as a bridge to alloHSCT but represent an ultra-high-risk group with poor overall survival. Further studies, including novel consolidation and treatment sequence, may improve outcomes of these patients.

POSC363 Engaging Patients and Caregivers in Health Economic Evaluations: Generating Stakeholder Input to Inform the Conduct of an Early Economic Evaluation of Chimeric Antigen Receptor T-Cell Therapy

Stakeholder engagement in health technology assessment is not new; however, little is known about specific processes of engagement during the conduct of the assessment, especially for economic evaluations. Patients and their caregivers have insight that can enhance the scope and validity of an economic model, though are often not engaged in such studies. We sought to address this within a study that involved patients and their caregivers in the conduct of an early economic evaluation of Chimeric Antigen Receptor T-cell therapy for adults with relapsed or refractory B-cell acute lymphoblastic leukemia to inform a more realistic estimate of potential treatment value.

Disease Burden Affects Outcomes in Pediatric and Young Adult B-Cell Lymphoblastic Leukemia After Commercial Tisagenlecleucel: A Pediatric Real-World Chimeric Antigen Receptor Consortium Report.

Tisagenlecleucel is a CD19-specific chimeric antigen receptor T-cell therapy, US Food and Drug Administration-approved for children, adolescents, and young adults (CAYA) with relapsed and/or refractory (RR) B-cell acute lymphoblastic leukemia (B-ALL). The US Food and Drug Administration registration for tisagenlecleucel was based on a complete response (CR) rate of 81%, 12-month overall survival (OS) of 76%, and event-free survival (EFS) of 50%. We report clinical outcomes and analyze covariates of outcomes after commercial tisagenlecleucel. We conducted a retrospective, multi-institutional study of CAYA with RR B-ALL across 15 US institutions, who underwent leukapheresis shipment to Novartis for commercial tisagenlecleucel. A total of 200 patients were included in an intent-to-treat response analysis, and 185 infused patients were analyzed for survival and toxicity. Intent-to-treat analysis demonstrates a 79% morphologic CR rate (95% CI, 72 to 84). The infused cohort had an 85% CR (95% CI, 79 to 89) and 12-month OS of 72% and EFS of 50%, with 335 days of median follow-up. Notably, 48% of patients had low-disease burden (< 5% bone marrow lymphoblasts, no CNS3, or other extramedullary disease), or undetectable disease, pretisagenlecleucel. Univariate and multivariate analyses associate high-disease burden (HB, ≥ 5% bone marrow lymphoblasts, CNS3, or non-CNS extramedullary) with inferior outcomes, with a 12-month OS of 58% and EFS of 31% compared with low-disease burden (OS; 85%, EFS; 70%) and undetectable disease (OS; 95%, EFS; 72%; P < .0001 for OS and EFS). Grade ≥ 3 cytokine release syndrome and neurotoxicity rates were 21% and 7% overall and 35% and 9% in patients with HB, respectively. Commercial tisagenlecleucel in CAYA RR B-ALL demonstrates efficacy and tolerability. This first analysis of commercial tisagenlecleucel stratified by disease burden identifies HB preinfusion to associate with inferior OS and EFS and increased toxicity.

Preclinical Evaluation of a Novel Dual Targeting PI3Kδ/BRD4 Inhibitor, SF2535, in B-Cell Acute Lymphoblastic Leukemia.

The PI3K/Akt pathway—and in particular PI3Kδ—is known for its role in drug resistant B-cell acute lymphoblastic leukemia (B-ALL) and it is often upregulated in refractory or relapsed B-ALL. Myc proteins are transcription factors responsible for transcribing pro-proliferative genes and c-Myc is often overexpressed in cancers. The chromatin regulator BRD4 is required for expression of c-Myc in hematologic malignancies including B-ALL. Previously, combination of BRD4 and PI3K inhibition with SF2523 was shown to successfully decrease Myc expression. However, the underlying mechanism and effect of dual inhibition of PI3Kδ/BRD4 in B-ALL remains unknown. To study this, we utilized SF2535, a novel small molecule dual inhibitor which can specifically target the PI3Kδ isoform and BRD4. We treated primary B-ALL cells with various concentrations of SF2535 and studied its effect on specific pharmacological on-target mechanisms such as apoptosis, cell cycle, cell proliferation, and adhesion molecules expression usingin vitro and in vivo models. SF2535 significantly downregulates both c-Myc mRNA and protein expression through inhibition of BRD4 at the c-Myc promoter site and decreases p-AKT expression through inhibition of the PI3Kδ/AKT pathway. SF2535 induced apoptosis in B-ALL by downregulation of BCL-2 and increased cleavage of caspase-3, caspase-7, and PARP. Moreover, SF2535 induced cell cycle arrest and decreased cell counts in B-ALL. Interestingly, SF2535 decreased the mean fluorescence intensity (MFI) of integrin α4, α5, α6, and β1 while increasing MFI of CXCR4, indicating that SF2535 may work through inside-out signaling of integrins. Taken together, our data provide a rationale for the clinical evaluation of targeting PI3Kδ/BRD4 in refractory or relapsed B-ALL using SF2535.

Blinatumomab Nonresponse and High-Disease Burden Are Associated With Inferior Outcomes After CD19-CAR for B-ALL.

CD19-targeted chimeric antigen receptor T cells (CD19-CAR) and blinatumomab effectively induce remission in relapsed or refractory B-cell acute lymphoblastic leukemia (ALL) but are also associated with CD19 antigen modulation. There are limited data regarding the impact of prior blinatumomab exposure on subsequent CD19-CAR outcomes. We conducted a multicenter, retrospective review of children and young adults with relapsed or refractory ALL who received CD19-CAR between 2012 and 2019. Primary objectives addressed 6-month relapse-free survival (RFS) and event-free survival (EFS), stratified by blinatumomab use. Secondary objectives included comparison of longer-term survival outcomes, complete remission rates, CD19 modulation, and identification of factors associated with EFS. Of 420 patients (median age, 12.7 years; interquartile range, 7.1-17.5) treated with commercial tisagenlecleucel or one of three investigational CD19-CAR constructs, 77 (18.3%) received prior blinatumomab. Blinatumomab-exposed patients more frequently harbored KMT2A rearrangements and underwent a prior stem-cell transplant than blinatumomab-naïve patients. Among patients evaluable for CD19-CAR response (n = 412), blinatumomab nonresponders had lower complete remission rates to CD19-CAR (20 of 31, 64.5%) than blinatumomab responders (39 of 42, 92.9%) or blinatumomab-naive patients (317 of 339, 93.5%), P < .0001. Following CD19-CAR, blinatumomab nonresponders had worse 6-month EFS (27.3%; 95% CI, 13.6 to 43.0) compared with blinatumomab responders (66.9%; 95% CI, 50.6 to 78.9; P < .0001) or blinatumomab-naïve patients (72.6%; 95% CI, 67.5 to 77; P < .0001) and worse RFS. High-disease burden independently associated with inferior EFS. CD19-dim or partial expression (preinfusion) was more frequently seen in blinatumomab-exposed patients (13.3% v 6.5%; P = .06) and associated with lower EFS and RFS. With the largest series to date in pediatric CD19-CAR, and, to our knowledge, the first to study the impact of sequential CD19 targeting, we demonstrate that blinatumomab nonresponse and high-disease burden were independently associated with worse RFS and EFS, identifying important indicators of long-term outcomes following CD19-CAR.