Abstract: Childhood Cancer Data Initiative is a national commitment to harnessing data in ways that accelerate childhood cancer research.

Abstract: Tisagenlecleucel is indicated 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 (DLBCL). The tisagenlecleucel chimeric antigen receptor (CAR) contains a murine single-chain variable fragment domain; we examined the effects of humoral and cellular immune responses to tisagenlecleucel on clinical outcomes using 2 validated assays. Data were pooled from the ELIANA (registered at www.clinicaltrials.gov as #NCT02435849) and ENSIGN (#NCT02228096) trials in r/r B-ALL (N = 143) and the JULIET trial (#NCT02445248) in r/r DLBCL (N = 115). Humoral responses were determined by flow cytometric measurement of anti-murine CAR19 (mCAR19) antibodies in serum. Cellular responses were determined using T-cell production of interferon-γ in response to 2 different pools of mCAR19 peptides. Pretreatment anti-mCAR19 antibodies were detected in 81% of patients with r/r B-ALL and 94% of patients with r/r DLBCL. Posttreatment anti-mCAR19 antibodies were higher than patient-specific baseline in 42% of r/r B-ALL and 9% of r/r DLBCL patients. Pretreatment and posttreatment anti-mCAR19 antibodies did not affect tisagenlecleucel cellular kinetics, including maximum concentration and persistence (r2 & lt; 0.05), clinical response (day-28 response, duration of response, and event-free survival), and safety. T-cell responses were consistent over time, with net responses & lt;1% at baseline and posttreatment time points in a majority of patients and no effect on transgene expansion or persistence or outcomes. Presence of baseline and/or posttreatment anti-mCAR19 antibodies or T-cell responses did not alter the activity of tisagenlecleucel in patients with r/r B-ALL or r/r DLBCL.

Abstract: Introduction: Chimeric antigen receptor (CAR) T-cells redirected against CD19 have demonstrated remarkable clinical activity in children and adults with relapsed/refractory (r/r) B-cell malignancies. The risk of lineage switch (LS) following CD19-directed therapies has been well documented but has been primarily limited to case reports. Additionally, the risk of subsequent malignant neoplasms (SMN) following CAR T-cells has not yet been described. Distinguishing LS (B-ALL to myeloid malignancy) from a therapy-related myeloid neoplasm is both clinically and biologically relevant. The former emerges from a highly refractory leukemic clone, likely resistant to salvage therapy, whereas the latter represents a new malignancy that can be associated with long-term survival. Methods: We conducted a multicenter, retrospective review of children and young adults with r/r B-acute lymphoblastic leukemia (B-ALL) who received either commercial tisagenlecleucel or 1 of 3 investigational murine-based CD19-CAR constructs on clinical trials at 7 US centers between 2012-2019. Patients diagnosed with B-ALL before age 25 years were included and patients who had received any prior CAR product were excluded. Results: Of 420 CAR-treated patients, with a median follow-up of 30.1 months, 12 (2.9%) experienced LS and 6 (1.4%) developed a SMN (Table). The median time to diagnosis of LS following CAR T-cell infusion was significantly shorter compared to diagnosis of SMN (65.5 days vs. 883.5 days; p=0.005). Eleven of 12 patients (91.7%) with LS converted to acute myeloid leukemia (AML). One patient converted to mixed phenotype acute leukemia, B/myeloid type. The leukemia of 10 of 12 patients with LS harbored cytogenetics similar to those at initial diagnosis. For the remaining 2 patients with LS, cytogenetics were unavailable, but the leukemias were considered LS by the treating institution. KMT2Ar rearrangement (KMT2Ar) was a predominant cytogenetic abnormality seen in patients with LS. Overall, 38 of 420 patients (9%) had a KMT2Ar. KMT2Ar was present in 9 of 12 (75%) patients with LS compared to 20 of 408 (7.1%) non-LS patients (p & lt;0.001). Patients with LS were younger at initial diagnosis compared to the remaining cohort (median age, 1.6 years vs. 7.7 years; p=0.001), reflecting the inherent association between KMT2Ar and infant ALL. Otherwise, there were no significant differences in gender, prior hematopoietic stem cell transplant (HSCT), prior blinatumomab exposure, or CAR response. Within the KMT2Ar cohort, 31 (81.6%) patients achieved a complete remission post-CAR. Eight of these patients received a consolidative HSCT (representing 4 first and 4 second HSCTs). No KMT2Ar patient experienced a post-HSCT LS and 3 are alive with a median follow-up of 1164 days post-CAR. In contrast, of the 23 KTM2Ar patients who did not receive HSCT post-CAR, 7 developed LS and 14 are alive with a median follow-up of 864 days post-CAR. Relative contraindications to post-CAR HSCT included a prior HSCT (n=11) or early LS (n=5). Of the 7 CAR non-responding patients with KMT2Ar, 2 (28.6%) had rapid emergence of LS by the first restaging timepoint. There are no long-term survivors following LS, regardless of KMT2A status, dying a median of 123 days (range, 36-594 days) after diagnosis of LS. The 6 SMNs were cholangiocarcinoma, synovial sarcoma, malignant melanoma and 3 therapy-related myeloid neoplasms (MDS/AML), distinguished from LS based on loss of original cytogenetics. Notably, 4/6 (67%) patients that developed a SMN had received an allogeneic HSCT prior to development of SMN. Four patients (67%) remain alive and in remission with a median follow-up of 304 days after diagnosis of SMN, including 2 patients with MDS/AML. Conclusions: In the largest series of pediatric patients treated with CAR T-cell therapy, we show that LS occurs in 2.9% of children. The presence of a KMT2Ar was the biggest risk factor, with 23.7% of these patients experiencing LS. We found that LS can occur very early in a patient's post CAR T-cell course, and despite a variety of treatment approaches, the outcomes for these patients are dismal. Given the predisposition to LS, the role for consolidative HSCT in KMT2Ar patients warrants further study. Limited by a short follow-up period, we saw SMNs in only 1.4% of our patients. Causality is unknown and likely unrelated to CAR-T, but this further supports the long-term safety of CAR T-cells in children with B-ALL. Figure 1 Figure 1. Disclosures Borowitz: Amgen, Blueprint Medicines: Honoraria. Lee: Harpoon Therapeutics: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Other: trial funding; Gilead: Other: trial funding. Grupp: Novartis, Adaptimmune, TCR2, Cellectis, Juno, Vertex, Allogene and Cabaletta: Other: Study steering committees or scientific advisory boards; Novartis, Roche, GSK, Humanigen, CBMG, Eureka, and Janssen/JnJ: Consultancy; Novartis, Kite, Vertex, and Servier: Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Steering committee, Research Funding. Verneris: jazz: Other: advisory board; Novartis: Other: advisory board; Fate Therapeutics: Consultancy. Gore: Mirati: Current equity holder in publicly-traded company; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Honoraria; Clovis: Current equity holder in publicly-traded company; Celgene: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Sanofi Paris: Current equity holder in publicly-traded company; Anchiano: Current equity holder in publicly-traded company; Blueprint Medicines: Current equity holder in publicly-traded company. Brown: Novartis: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Kura: Membership on an entity's Board of Directors or advisory committees; KIte: Membership on an entity's Board of Directors or advisory committees. Pulsipher: Equillium: Membership on an entity's Board of Directors or advisory committees; Adaptive: Research Funding; Jasper Therapeutics: Honoraria. Rheingold: Pfizer: Research Funding; Optinose: Other: Spouse's current employment. Gardner: BMS: Patents & Royalties; Novartis: Consultancy.

Abstract: A single-center trial of CD19 directed, lentiviral transduced chimeric antigen receptor (CAR) T cells (CTL019) for relapsed and refractory (r/r) B-ALL pediatric patients showed rates of CR 〉 90% with prolonged CAR T cell persistence/CR without further therapy in the majority of patients infused (Maude NEJM 2014). We report here the feasibility, safety and efficacy of the first multicenter global pivotal registration CAR T cell trial. Features of this trial include: i) the first trial in which industry-manufactured cells were provided to all patients; ii) enrollment across 25 centers in the US, EU, Canada, Australia, and Japan; iii) successful transfer and manufacturing of cells in a global supply chain; and iv) successful implementation of cytokine release syndrome (CRS) management across a global trial. All patients had CD19 positive B-ALL with morphologic marrow tumor involvement at registration ( 〉 5% blasts), and were either primary refractory; chemo-refractory after first relapse, relapsed after second line therapy; or ineligible for allogeneic SCT. CTL019 was manufactured from patient PBMC under GMP conditions in the US, at a centralized "sponsor-owned" manufacturing facility, and supplied to all sites. The primary endpoint of overall remission rate (CR+CRi) within 3 months and secondary endpoints (EFS, DOR, OS and safety) were assessed by an independent review committee. Based on preliminary data as of March 2016, 57 patients were enrolled. There were 3 manufacturing failures (5%), 5 patients were not infused due to death or adverse events (9%), and 15 patients were pending infusion at the data cut off. Following fludarabine/cyclophosphamide lymphodepleting chemotherapy in the majority of the patients, 34 patients (median age 11 [3-23], 50% with prior HSCT) were infused with a single dose of CTL019 at a median dose of 2.9 x106 transduced CTL019 cells/kg (0.2 to 4). Among 29 patients reaching D28 prior to the data cutoff, 83% (24/29) achieved CR or CRi by local investigator assessment, all of which were MRD-negative. Two early deaths occurred prior to initial disease assessment, one due to disease progression and one due to intracranial hemorrhage. Two patients did not respond. One patient was in CR by BM at D28, but CSF was not assessed, therefore this patient was classified as "incomplete" assessment. Safety was managed by a protocol-specified CRS algorithm with no cases of refractory CRS. Using the Penn CRS grading scale, 82% of patients experienced CRS, with 7 grade 3 (21%) and 8 grade 4 (24%) events. 44% patients with CRS required anti-cytokine therapy; all received tocilizumab with or without other anti-cytokine therapy, with complete resolution of CRS. Besides CRS, the most common grade 3 and 4 non-hematologic AEs were febrile neutropenia (29%), increased bilirubin (21%), increased AST (21%), and hypotension (21%). 21% of patients experienced grade 3 or 4 neuropsychiatric events including confusion, delirium, encephalopathy, agitation and seizure; no cerebral edema was reported. CTL019 in vivo cellular kinetics by qPCR demonstrated transgene persistence in blood in responding patients at and beyond 6 months. Overall exposure (AUC 0-28d) and maximal expansion (Cmax) of CTL019 DNA measured by qPCR was higher in responding compared with non-responding patients. In summary, this pivotal global study in pediatric and young adult patients with r/r B-ALL receiving CTL019, confirms a high level of efficacy and a similar safety profile to that shown in the prior single center experience. Safety was effectively and reproducibly managed by appropriately trained investigators. The study has completed accrual. At the meeting, updated data from a planned formal interim analysis including safety, efficacy (primary and selected secondary endpoints), cellular kinetics, and impact of anti-cytokine therapy will be presented for more than 50 patients infused at 25 global sites. Disclosures Grupp: Jazz Pharmaceuticals: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy. Laetsch:Novartis: Consultancy; Loxo Oncology: Consultancy. Bittencourt:Seattle Genetics: Consultancy; Jazz Pharmaceuticals: Consultancy, Other: Educational Grant. Maude:Novartis: Consultancy. Myers:Novartis Pharmaceuticals: Consultancy. Rives:Novartis: Consultancy; Jazz Pharma: Consultancy. Nemecek:Medac, GmbH: Research Funding; Novartis: Consultancy; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees. Schlis:Novartis: Honoraria. Martin:Jazz Pharmaceuticals: Other: One time discussion panel; Novartis: Other: Support of clinical trials. Bader:Medac: Consultancy, Research Funding; Riemser: Research Funding; Neovii Biotech: Research Funding; Servier: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Peters:Novartis: Consultancy; Jazz: Speakers Bureau; Amgen: Consultancy; Pfizer: Consultancy; Medac: Consultancy. Biondi:Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; Cellgene: Other: Advisory Board; BMS: Membership on an entity's Board of Directors or advisory committees. Baruchel:Servier: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Jazz: Consultancy; Baxalta: Research Funding. June:University of Pennsylvania: Patents & Royalties; Johnson & Johnson: Research Funding; Celldex: Consultancy, Equity Ownership; Pfizer: Honoraria; Immune Design: Consultancy, Equity Ownership; Novartis: Honoraria, Patents & Royalties: Immunology, Research Funding; Tmunity: Equity Ownership, Other: Founder, stockholder . Sen:Novartis: Employment. Zhang:Novartis: Employment. Thudium:Novartis: Employment. Wood:Novartis Pharmaceuticals: Employment, Other: Stock. Taran:Novartis: Employment. Pulsipher:Chimerix: Consultancy; Jazz Pharmaceutical: Consultancy; Novartis: Consultancy, Other: Study Steering Committee; Medac: Other: Housing support for conference.

Abstract: Olaratumab is a monoclonal antibody that specifically binds to platelet‐derived growth factor receptor alpha (PDGFRα) and blocks receptor activation. We conducted a phase 1 trial to evaluate the safety of olaratumab and determine a recommended dose in combination with three different chemotherapy regimens in children. Patients 〈 18 years with relapsed/refractory solid or central nervous system tumors were enrolled to two dose levels of olaratumab. Patients received olaratumab monotherapy at 15 mg/kg (Part A) or 20 mg/kg (Part B) on Days 1 and 8 of the first 21‐day cycle, followed by olaratumab combined with standard fixed doses of chemotherapy with doxorubicin, vincristine/irinotecan, or high‐dose ifosfamide by investigator choice for subsequent 21‐day cycles. In Part C, patients received olaratumab 20 mg/kg plus assigned chemotherapy for all cycles. Parts A‐C enrolled 68 patients across three chemotherapy treatment arms; olaratumab in combination with doxorubicin (N = 16), vincristine/irinotecan (N = 26), or ifosfamide (N = 26). Three dose‐limiting toxicities (DLTs) occurred during olaratumab monotherapy (at 15 mg/kg, grade [G] 4 alanine aminotransferase [ALT] ; at 20 mg/kg, G3 lung infection and G3 gamma‐glutamyl transferase). One DLT occurred during vincristine/irinotecan with olaratumab 20 mg/kg therapy (G3 ALT). Treatment‐emergent adverse events ≥G3 in 〉 25% of patients included neutropenia, anemia, leukopenia, lymphopenia, and thrombocytopenia. Pharmacokinetic profiles of olaratumab with chemotherapy were within the projected range based on adult data. There was one complete response (rhabdomyosarcoma [Part B vincristine/irinotecan arm]) and three partial responses (two rhabdomyosarcoma [Part A doxorubicin arm and Part C doxorubicin arm] ; one pineoblastoma [Part B vincristine/irinotecan arm]). Olaratumab was tolerable and safely administered in combination with chemotherapy regimens commonly used in children and adolescents.

Abstract: Tisagenlecleucel is a chimeric antigen receptor–T cell therapy that facilitates the killing of CD19 + B cells. A model was developed for the kinetics of tisagenlecleucel and the impact of therapies for treating cytokine release syndrome (tocilizumab and corticosteroids) on expansion. Data from two phase II studies in pediatric and young adult relapsed/refractory B cell acute lymphoblastic leukemia were pooled to evaluate this model and evaluate extrinsic and intrinsic factors that may impact the extent of tisagenlecleucel expansion. The doubling time, initial decline half‐life, and terminal half‐life for tisagenlecleucel were 0.78, 4.3, and 220 days, respectively. No impact of tocilizumab or corticosteroids on the expansion rate was observed. This work represents the first mixed‐effect model‐based analysis of chimeric antigen receptor–T cell therapy and may be clinically impactful as future studies examine prophylactic interventions in patients at risk of higher grade cytokine release syndrome and the effects of these interventions on chimeric antigen receptor–T cell expansion.

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.