Abstract: Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. In the primary analysis of the global phase II ELIANA trial (ClinicalTrials.gov identifier: NCT02435849 ), tisagenlecleucel provided an overall remission rate of 81% in pediatric and young adult patients with relapsed or refractory B-cell acute lymphoblastic leukemia (R/R B-ALL), with 59% of responders remaining relapse-free at 12 months. Here, we report an update on efficacy, safety, and patient-reported quality of life in 79 pediatric and young adult patients with R/R B-ALL following a median follow-up of 38.8 months. The overall remission rate was 82%. The median event-free survival was 24 months, and the median overall survival was not reached. Event-free survival was 44% (95% CI, 31 to 57) and overall survival was 63% (95% CI, 51 to 73) at 3 years overall (most events occur within the first 2 years). The estimated 3-year relapse-free survival with and without censoring for subsequent therapy was 52% (95% CI, 37 to 66) and 48% (95% CI, 34 to 60), respectively. No new or unexpected long-term adverse events were reported. Grade 3/4 adverse events were reported in 29% of patients 〉 1 year after infusion; grade 3/4 infection rate did not increase 〉 1 year after infusion. Patients reported improvements in quality of life up to 36 months after infusion. These findings demonstrate favorable long-term safety and suggest tisagenlecleucel as a curative treatment option for heavily pretreated pediatric and young adult patients with R/R B-ALL.

Abstract: Introduction Chimeric antigen receptor (CAR) T cell therapy has been extremely efficacious in pediatric patients with multiply relapsed and/or refractory B-cell acute lymphoblastic leukemia (B-ALL) with overall remission rates of 81% by three months post-infusion (Maude et al., N Engl J Med, 2018), and achieved FDA approval for this indication. In order for the product to meet the standards of this approval for commercial release, both the leukapheresis and manufactured products must meet a variety of specific requirements, some of which are more stringent than those in these pivotal clinical trials. The Managed Access Program (MAP) provides access to tisagenlecleucel for patients with B-ALL or diffuse large B-cell lymphoma that is out of specification (OOS) for whom repeat leukapheresis is not feasible. Patients may also receive OOS tisagenlecleucel by applying for a single-patient Investigational New Drug (IND). Previous reports have shown no difference in efficacy or toxicity between patients receiving tisagenlecleucel that meets commercial release specifications and those receiving OOS tisagenlecleucel (Grupp, et al., Blood Abstr 614, 2019; Jaglowski, et al., Blood Abstr 627, 2019). This study seeks to evaluate outcomes in pediatric and young adult patients who received tisagenlecleucel via the MAP or a single-patient IND in our Pediatric Real World CAR Consortium (PRWCC). Methods Retrospective data were abstracted from the PRWCC database of patients with relapsed/refractory B-ALL from fifteen different US institutions who received tisagenlecleucel as an FDA-approved therapy outside the context of a clinical trial. Patients whose cellular product was obtained through the MAP (NCT03601442) or with single patient IND approval due having either a cryopreserved leukapheresis product and/or manufactured tisagenlecleucel that did not meet specifications for commercial release were categorized as MAP/IND and those whose product met all release criteria were categorized as standard of care (SOC). Results Among 185 total infused patients in our database, 24 (13%) received tisagenlecleucel either via the MAP (n=14) or a single patient IND (n=10). Baseline patient and disease characteristics were not significantly different for MAP/IND patients versus the SOC cohorts (Table 1). Median duration of follow-up post-CAR T cell infusion for these infused patients was 342.5 days (range 107-780) versus 318 days (range 6-863) for the SOC cohort (p=0.43). Reasons for products being OOS included cell viability & lt;80% (n=17), total nucleated cell count & lt;2x109 in leukapheresis product (n=3), failed interferon gamma release assay (n=2), cryopreserved leukapheresis product collected & gt;9 months prior (n=1), and determination of residual beads & gt;50 beads/3x106cells (n=1). Overall survival at 6- and 12-months was 96% versus 83% and 85% versus 70% for the MAP/IND versus SOC, respectively. Event-free survival at 6- and 12-months was 65% versus 63% and 55% versus 51%, respectively. Probability of continued remission at 6- and 12-months among patients who achieved a complete remission (CR) at day 28 was 79% versus 75% and 66% versus 63% for the MAP/IND versus SOC, respectively (Figure 1). Comparing toxicities between patients in the MAP/IND versus SOC cohorts, cytokine release syndrome (CRS, any grade) occurred in 46% versus 61%, CRS ( & gt;grade 3) in 17% versus 19%, immune effector cell-associated neurotoxicity syndrome (ICANS) in 8% versus 22%, and infectious complications in 54% vs. 37%, respectively (p=ns for all). Conclusions In our retrospective cohort evaluating the use of tisagenlecleucel to treat pediatric and young adult patients with relapsed/refractory B-ALL in the real-world setting, neither the efficacy nor safety of tisagenlecleucel seem to be compromised by use of products OOS for commercial release. Larger studies are needed to further delineate specific cut-offs outside of which either efficacy and/or safety may truly be impacted. Disclosures Phillips: Novartis: Membership on an entity's Board of Directors or advisory committees. Stefanski:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Margossian:Novartis: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Verneris:Novartis: Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Consultancy, Current equity holder in publicly-traded company; Bmogen: Consultancy, Current equity holder in publicly-traded company; Uptodate: Consultancy. Myers:Novartis: Consultancy, Honoraria, Other: ELIANA trial Steering Committee, Speakers Bureau. Brown:Janssen: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Qayed:Mesoblast: Consultancy; Novartis: Consultancy. Hermiston:Novartis: Membership on an entity's Board of Directors or advisory committees; Sobi: Membership on an entity's Board of Directors or advisory committees. Satwani:Mesoblast: Consultancy; Takeda: Consultancy. Curran:Novartis: Consultancy, Research Funding; Celgene: Research Funding; Mesoblast: Consultancy. Mackall:Apricity Health: Consultancy, Current equity holder in private company; Lyell Immunopharma: Consultancy, Current equity holder in private company; BMS: Consultancy; Nektar Therapeutics: Consultancy; Allogene: Current equity holder in publicly-traded company; NeoImmune Tech: Consultancy. Laetsch:Novartis: Consultancy, Research Funding; Bayer: Research Funding; Pfizer: Research Funding; Cellectis: Consultancy.

Abstract: Background: Tisagenlecleucel is an anti-CD19 chimeric antigen receptor (CAR)-T cell therapy approved for pediatric and young adult patients with relapsed/refractory (r/r) B-cell acute lymphoblastic leukemia (B-ALL) and adult patients with r/r diffuse large B-cell lymphoma. The ELIANA trial showed efficacy (81% overall remission rate [ORR]; 60% complete remission [CR] ) and safety of tisagenlecleucel in r/r B-ALL (Maude et al. N Engl J Med. 2018). In the ELIANA trial, sustained remissions were associated with B-cell aplasia, an expected on-target effect of tisagenlecleucel and a pharmacodynamic marker for tisagenlecleucel persistence. In some patients who demonstrated short CAR-T cell persistence, reinfusion with 1 or more additional doses of tisagenlecleucel has restored B-cell aplasia and produced a 60% CR rate in patients who were reinfused with humanized CD19-targeted CAR-T cell therapy (Maude et al. J Clin Oncol. 2016). This prolongs the period of tisagenlecleucel activity and immunosurveillance and may therefore prolong durable remission. We introduce a trial in progress investigating the efficacy and safety of tisagenlecleucel reinfusion in pediatric and young adult patients with B-ALL experiencing a loss of B-cell aplasia. Study Design and Methods: HESTER (NCT04225676) is a phase II, open-label, multicenter trial to determine the efficacy and safety of tisagenlecleucel reinfusion in pediatric and young adult patients with B-ALL experiencing loss of B-cell aplasia. Eligible patients must be ≤25 years of age with a confirmed diagnosis of CD19(+) leukemia. Patients must have been previously infused with commercial tisagenlecleucel and have at least 1 additional dose of commercial tisagenlecleucel prescribed to them in the course of medical practice. Commercial tisagenlecleucel must be given for reinfusion within 9 months of the initial manufacturing date. Patients must have loss of B-cell aplasia defined as peripheral blood (PB) absolute B lymphocyte count ≥50/μL or PB B lymphocyte ≥10% of the total lymphocytes; patients are not required to be minimal residual disease negative (MRD)(-). Karnofsky (age ≥16 years) or Lansky (age & lt;16 years) performance status must be ≥50 at screening. Patients treated with prior gene/adoptive T-cell therapy other than tisagenlecleucel and patients with active central nervous system involvement by malignancy are excluded. The primary efficacy endpoint is the proportion of patients who reestablish B-cell aplasia within 12 months of reinfusion as measured by circulating B lymphocytes ( & lt;50/μL) and presence of tisagenlecleucel cells by quantitative polymerase chain reaction (qPCR) in the PB. Secondary outcomes include the ORR (CR + CR with incomplete blood count recovery) during the 12 months post reinfusion, event-free survival, overall survival, MRD status, and safety; immunogenicity and tisagenlecleucel persistence (by qPCR) are exploratory endpoints. Subgroup analysis of efficacy outcomes will include patients with a loss of B-cell aplasia within 9 months of first infusion who are MRD(+) at time of enrollment, as well as patients with very early ( & lt;3 mo), early (≤3 to & lt;6 mo), and later (≥6 mo) loss of B-cell aplasia following first infusion. Safety will be assessed throughout the trial. For the primary analysis, a minimum of 10% of patients reestablishing B-cell aplasia within 12 months after reinfusion is expected with an estimated true rate of 25%. All secondary and exploratory variables will be summarized descriptively. Estimated enrollment is about 54 patients in the United States. Clinical Trial Information: NCT04225676 Disclosures Boyer: Thunder Biotech Inc: Consultancy. Grupp:Servier: Research Funding; Cellectis: Other; Roche: Consultancy; Adaptimmune: Other: SAB; Jazz: Other: SSC; TCR2: Other: SAB; GlaxoSmithKline: Consultancy; CRISPR Therapeutics/Vertex Pharmaceuticals: Other; Juno/BMS: Other; Janssen/JnJ: Consultancy; Humanigen: Consultancy; CBMG: Consultancy; Kite/Gilead: Research Funding; Allogene: Other; Novartis: Consultancy, Other: SSC, Research Funding. Hermiston:Novartis: Membership on an entity's Board of Directors or advisory committees; Sobi: Membership on an entity's Board of Directors or advisory committees. Kovacs:Novartis: Current Employment. Magley:Novartis: Current Employment. Myers:Novartis: Consultancy, Honoraria, Other: ELIANA trial Steering Committee, Speakers Bureau. Phillips:Novartis: Membership on an entity's Board of Directors or advisory committees. Pulsipher:Bellicum: Honoraria; Mesoblast: Honoraria; Miltenyi: Honoraria, Research Funding; Adaptive: Research Funding; Novartis: Honoraria; Jasper: Honoraria. Purkayastha:Novartis: Current Employment. Willert:Novartis: Current Employment.

Abstract: Introduction Detection of minimal residual disease (MRD) is an important predictor of patient outcome following treatment of B-cell acute lymphoblastic leukemia (B-ALL). We assessed concordance between two MRD assays, with different assay sensitivities, to determine which MRD detection method could support early relapse detection. Immunoglobulin next generation sequencing (Ig NGS) and flow cytometry (FC) were tested in samples from two clinical trials ELIANA (NCT02435849) and ENSIGN (NCT02228096) for pediatric relapsed and refractory B-ALL patients treated with tisagenlecleucel. We also assessed whether using blood with Ig NGS would be comparable to BM testing with FC. Finally we analyzed whether clonal evolution, as detected by Ig NGS, occurred during of the course of therapy for both CD19+ and CD19- relapse patients. Methods In this analysis, bone marrow and peripheral blood specimens at screening (pre-tisagenlecleucel infusion), post-infusion and relapse were tested. Ig NGS was performed in 300 samples from 88 patients. 237 samples from 83 patients also had FC MRD results available. MRD was measured on fresh blood and bone marrow using a 3-tube FC assay (CD10, CD19, CD13, CD20, CD22, CD33, CD34, CD38, CD45, CD58, CD123). The FC MRD assay has a lower limit of sensitivity of 0.01% of white blood cells. Ig NGS detection of MRD was performed using the Adaptive Biotechnology's NGS MRD assay. MRD quantitative values, along with the qualitative MRD calls at each assay sensitivity level (10-4, 10-5 and 10-6) were reported. At baseline, 85 out of 88 samples had informative clones. Results and Conclusions To examine the comparability of flow cytometry and Ig NGS methods in assessing MRD, baseline and post-treatment samples were tested. Baseline samples, which had a high disease burden, showed 100% MRD concordance between both assays. However, post-treatment, where the leukemic burden was dramatically reduced, Ig NGS detected a greater number of MRD positive samples compared to FC, at each sensitivity level tested (10-4, 10-5 and 10-6). At the highest sensitivity level of 10-6, Ig NGS was able to detect 18% more MRD positive post-treatment samples. Importantly, Ig NGS was able to detect MRD positivity 1-4 months ahead of clinical relapse in a small number of relapsed patients, whether relapse was CD19+ or CD19-. This may provide an important window of opportunity for pre-emptive treatment while a patients' tumor burden is still low. In B-ALL, it has previously been described that MRD levels can be one to three logs lower in blood compared to bone marrow (VanDongen JJ et al. Blood 2015). Our results support these findings whereby MRD burden in bone marrow was higher than in blood using both FC and Ig NGS. We next set out to determine if the increased sensitivity afforded by the Ig NGS assay could provide a level of MRD detection in the blood comparable to FC in the bone marrow. In patients with matching data available, Ig NGS was able to detect more MRD positive blood samples than FC MRD positive bone marrow samples. This suggests that monitoring of MRD using Ig NGS in the blood holds the potential to be used as a surrogate for FC MRD in bone marrow. The relationship between MRD and prognosis was examined. Patients who were MRD negative by both Ig NGS and FC at the end of first month post-infusion had better progression-free survival and overall survival compared to those with detectable MRD. Tumor clonality will be further analyzed to understand sub-clone composition at baseline and clonal evolution following tisagenlecleucel treatment. Taken together, these results highlight the importance of using a highly sensitive assay, such as Ig NGS, when monitoring for MRD. MRD detection by Ig NGS holds the potential to identify early response/relapse in patients, which could provide a window of opportunity for additional intervention before morphological relapse. Ongoing studies with larger patient groups will provide further information on the applicability of Ig NGS MRD detection and its association with long-term outcome in tisagenlecleucel-treated pediatric r/r B-ALL patients. Disclosures Pulsipher: Novartis: Consultancy, Honoraria, Speakers Bureau; CSL Behring: Consultancy; Amgen: Honoraria; Adaptive Biotech: Consultancy, Research Funding. Han:Novartis Pharmaceuticals Corporation: Employment, Equity Ownership. Quigley:Novartis Pharmaceuticals Corporation: Employment. Kari:Adaptimmune LLC: Other: previous employment within 2 years; Novartis Pharmaceuticals Corporation: Employment. Rives:Shire: Consultancy, Other: Symposia, advisory boards ; Amgen: Consultancy, Other: advisory board ; Novartis Pharmaceuticals Corporation: Consultancy, Other: Symposia, advisory boards ; Jazz Pharma: Consultancy, Other: Symposia, advisory boards . Laetsch:Bayer: Consultancy; Eli Lilly: Consultancy; Pfizer: Equity Ownership; Novartis Pharmaceuticals Corporation: Consultancy; Loxo Oncology: Consultancy. Myers:Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Research Funding, Speakers Bureau. Qayed:Novartis: Consultancy. Stefanski:Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Speakers Bureau. Baruchel:Shire: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy; Servier: Consultancy; Roche: Consultancy; Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Travel, accommodations or expenses; Celgene: Consultancy. Bader:Cellgene: Consultancy; Riemser: Research Funding; Medac: Patents & Royalties, Research Funding; Neovii: Research Funding; Novartis: Consultancy, Speakers Bureau. Yi:Novartis Pharmaceuticals Corporation: Employment. Kalfoglou:Novartis Pharmaceuticals Corporation: Employment. Robins:Adaptive Biotechnologies: Consultancy, Employment, Equity Ownership, Patents & Royalties. Yusko:Adaptive Biotechnologies: Employment, Equity Ownership. Görgün:Novartis Pharmaceuticals Corporation: Employment. Bleickardt:Novartis Pharmaceuticals Corporation: Employment. Wong:Novartis Pharmaceuticals Corporation: Employment, Equity Ownership. Grupp:Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; Adaptimmune: Consultancy; University of Pennsylvania: Patents & Royalties.

Abstract: 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]

Abstract: Chimeric antigen receptor (CAR) T cells provide a therapeutic option in hematologic malignancies. However, treatment failure after initial response approaches 50%. In allogeneic hematopoietic cell transplantation, optimal fludarabine exposure improves immune reconstitution, resulting in lower nonrelapse mortality and increased survival. We hypothesized that optimal fludarabine exposure in lymphodepleting chemotherapy before CAR T-cell therapy would improve outcomes. In a retrospective analysis of patients with relapsed/refractory B-cell acute lymphoblastic leukemia undergoing CAR T-cell (tisagenlecleucel) infusion after cyclophosphamide/fludarabine lymphodepleting chemotherapy, we estimated fludarabine exposure as area under the curve (AUC; mg × h/L) using a validated population pharmacokinetic (PK) model. Fludarabine exposure was related to overall survival (OS), cumulative incidence of relapse (CIR), and a composite end point (loss of B-cell aplasia [BCA] or relapse). Eligible patients (n = 152) had a median age of 12.5 years (range, & lt;1 to 26), response rate of 86% (n = 131 of 152), 12-month OS of 75.1% (95% confidence interval [CI], 67.6% to 82.6%), and 12-month CIR of 36.4% (95% CI, 27.5% to 45.2%). Optimal fludarabine exposure was determined as AUC ≥13.8 mg × h/L. In multivariable analyses, patients with AUC & lt;13.8 mg × h/L had a 2.5-fold higher CIR (hazard ratio [HR], 2.45; 95% CI, 1.34-4.48; P = .005) and twofold higher risk of relapse or loss of BCA (HR, 1.96; 95% CI, 1.19-3.23; P = .01) compared with those with optimal fludarabine exposure. High preinfusion disease burden was also associated with increased risk of relapse (HR, 2.66; 95% CI, 1.45-4.87; P = .001) and death (HR, 4.77; 95% CI, 2.10-10.9; P & lt; .001). Personalized PK-directed dosing to achieve optimal fludarabine exposure should be tested in prospective trials and, based on this analysis, may reduce disease relapse after CAR T-cell therapy.