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744 Phase I Trial Using CD19/CD22 Bispecific CAR T Cells in Pediatric and Adult Acute Lymphoblastic Leukemia (ALL)

Program: Oral and Poster Abstracts
Type: Oral
Session: 614. Acute Lymphoblastic Leukemia: Therapy, excluding Transplantation: Chemo Immuno and Targets--Improving Combinations in ALL
Hematology Disease Topics & Pathways:
CRS, Biological, ALL, Leukemia, Diseases, neurotoxicity, Therapies, Adverse Events, CAR-Ts, immunotherapy, Lymphoid Malignancies
Monday, December 9, 2019: 4:00 PM
W224CDGH, Level 2 (Orange County Convention Center)

Liora M Schultz, MD1, Lori S Muffly, MD2, Jay Y. Spiegel, MD, FRCPC3, Sneha Ramakrishna, MD4, Nasheed Hossain, MD5, Christina Baggott, RN, PhD6*, Bita Sahaf, PhD7*, Shabnum Patel, PhD8*, Juliana Craig, BA9*, Jenny Yoon10*, Meena Kadapakkam, MD11*, Robbie G. Majzner, MD12, Matthew J. Frank, MD, PhD13, Courtney Erickson4*, Anne Cunniffe Marcy, MSBH6*, Michelle Fujimoto14*, Neehar Bhatia15*, Everett H Meyer, MD, PhD2*, Katherine A. Kong16*, Emily Egeler17*, Sharon Mavroukakis18*, Haiying Qin, MS19*, Terry J. Fry, MD20, Steven A Feldman, PhD21*, David B Miklos, MD, PhD22, Crystal L. Mackall, MD23 and Kara L. Davis, DO23

1School of Medicine, Department of Pediatrics, Division of Hematology and Oncology, Stanford University, Palo Alto, CA
2Division of Blood and Marrow Transplantation, Department of Medicine, Stanford University Medical Center, Stanford, CA
3Department of Medicine, Division of Oncology, Stanford University School of Medicine, Stanford, CA
4Stanford University School of Medicine, Department of Pediatrics, Division of Hematology and Oncology, Palo Alto, CA
5Loyola University Medical Center, Maywood, IL
6Cancer Clinical Trials Office, Stanford University, Palo Alto, CA
7Stanford University Medical Center, Stanford, CA
8Stanford University, Palo Alto, CA
9Department of Medicine, Division of Blood and Marrow Transplantation, Stanford University School of Medicine, Palo Alto, CA
10Stanford University School of Medicine, Division of Blood and Marrow Transplantation, Palo Alto, CA
11Stanford University School of Medicine, Department of Pediatrics, Division of Hematology Oncology, Palo Alto, CA
12Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA
13Department of Medicine, Division of Blood and Marrow Transplantation, Stanford University, Stanford, CA
14Stanford University, Cancer Clinical Trials Office, CCTO, Palo Alto, CA
15Stanford University School of Medicine, Lab for Cell and Gene Medicine, Palo Alto, CA
16Center for Cancer Cell Therapy, Stanford University School of Medicine, South San Francisco, CA
17Stanford University, School of Medicine, Palo Alto, CA
18Stanford University Medical Center School of medicine, Stanford, CA
19Center for Cancer Research National Cancer Institute, Bethesda, MD
20CCR, NCI NIH, Aurora, CO
21Stanford University School of Medicine, Stanford, CA
22Division of Blood and Marrow Transplantation, Department of Medicine, Stanford University School of Medicine, Stanford, CA
23Department of Pediatrics, Stanford University School of Medicine, Stanford, CA

Introduction: Chimeric antigen receptor (CAR) T cells targeting either CD19 or CD22 have yielded striking complete remission (CR) rates of 70%-90% in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL), but CD19 negative and CD22 low relapse limits the curative potential of these single-antigen CAR T cell approaches. We hypothesized that a bivalent CAR-T construct that can target CD19 and/or CD22 would prevent antigen negative/low relapse. Here we present the combined single institution experience to date of pediatric and adult patients with R/R ALL treated with this novel bispecific CAR.

Methods: We conducted parallel Phase I clinical trials of CD19/CD22 bispecific CAR T cells in pediatric and adult patients with relapsed/refractory ALL. We utilized lentiviral transduction of a bivalent CAR construct incorporating the fmc63 CD19 and m971 CD22 single chain variable fragments (scFvs) and a 41BB costimulatory endodomain. After lymphodepletion with fludarabine and cyclophosphamide, patients were infused with fresh or cryopreserved CAR T cells manufactured using a 7-11 day process. Two dose levels were tested during dose escalation: Dose level 1 was 1x106 CAR T cells/kg and dose level 2 was 3x106 cells/kg. Primary objectives assessed the ability to successfully manufacture CAR19/22 CAR T cells and safety while response at Day 28 post-infusion was a secondary objective. Blood, bone marrow and cerebrospinal fluid samples were obtained at protocol defined intervals for correlative biology studies.

Results: Nineteen patients have been enrolled (10 pediatric; 9 adult) with a median age of 23 years (range, 2-68) and median of 4 (range, 2-11) prior lines of leukemia-directed therapy. Ten patients received prior HCT, 9 were treated with prior Blinatumomab, 3 with prior CD19 directed CAR T cells and 4 with prior Inotuzumab. Fourteen patients (8 pediatric, 6 adult) have been infused to date with CD19/CD22 bispecific CAR T cells; 7 were treated at dose level 1 (DL1) and 7 at dose level 2 (DL2). Successful manufacturing of cells at target dose levels was achieved in all patients. Twelve patients have reached day 28 and are included in the safety and response analysis presented here. Nine of 12 (75%) experienced cytokine release syndrome (CRS) and 2/12 (17%) developed immune-effector cell neurotoxicity syndrome (ICANS). The CRS and ICANS were all grade 1 or 2 across both dose levels and across pediatric and adult patients except for one adult with high disease burden who experienced grade 4 CRS and grade 4 ICANS, both of which were reversible. No differences in toxicities were seen across the patient age spectrum and there were no cases of treatment-related mortality within 28 days following CAR T infusion. Eleven of 12 (92%) patients achieved a CR, 10 of whom achieved CR at day 28 and one with a PR of extramedullary disease at day 28 which improved to CR by day 180 without further leukemia-directed intervention. One patient had primary progressive disease prior to day 28. Peak CAR expansion as detected by peripheral blood flow cytometry reached a median level of 11.13% (DL1) and 29.1% (DL2) CAR T of CD3+ cells with a range of 0.7-22.54% and 3.8-86.96%, respectively. To date, 3 patients (1 pediatric and 2 adult patients) have relapsed, all with retention of CD19. Post-remission practice differed across pediatric and adult patients; Six pediatric patients reaching day 28 underwent consolidative hematopoietic cell transplantation (HCT) whereas no adult patients received subsequent HCT. One patient died from complications post HCT while in remission. Therefore, the overall survival for all infused patients was 92% with a median follow-up of 9.5 months from time of infusion (range, 1-20).

Conclusion: The combined pediatric and adult phase I trials of bispecific CD19/CD22 targeting CAR T cells in relapsed/refractory ALL demonstrates safety and tolerability at two dose levels. Expanded accrual at dose level 2 is ongoing and clinical outcomes will be updated. This work additionally demonstrates feasibility of delivering unified B-ALL CAR T cell therapy across age boundaries. Multi-parametric CyTOF studies permitting CAR T cell phenotyping in conjunction with single cell TCR tracking, proteomics, epigenomics and cytokine profiling are ongoing and will be used to further characterize persisting CAR T cells and define inter-product and inter-patient variability.

Disclosures: Muffly: Pfizer: Consultancy; KITE: Consultancy; Adaptive: Research Funding; Amgen: Consultancy; Servier: Research Funding. Majzner: Xyphos Inc.: Consultancy; Lyell Immunopharma: Consultancy. Feldman: Octane Biotech, Inc.: Employment; Personalized Medicine Initiative Science: Membership on an entity's Board of Directors or advisory committees. Miklos: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Juno: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Becton Dickinson: Research Funding; Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees; AlloGene: Membership on an entity's Board of Directors or advisory committees. Mackall: Obsidian: Research Funding; Lyell: Consultancy, Equity Ownership, Other: Founder, Research Funding; Nektar: Other: Scientific Advisory Board; PACT: Other: Scientific Advisory Board; Bryologyx: Other: Scientific Advisory Board; Vor: Other: Scientific Advisory Board; Roche: Other: Scientific Advisory Board; Adaptimmune LLC: Other: Scientific Advisory Board; Glaxo-Smith-Kline: Other: Scientific Advisory Board; Allogene: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Apricity Health: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees.

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