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742 Development and Evaluation of a Human Single Chain Variable Fragment (scFv) Derived Bcma Targeted CAR T Cell Vector Leads to a High Objective Response Rate in Patients with Advanced MM

Myeloma: Therapy, excluding Transplantation
Program: Oral and Poster Abstracts
Type: Oral
Session: 653. Myeloma: Therapy, excluding Transplantation I
Monday, December 11, 2017: 3:30 PM
Bldg C, Lvl 1, Hall C1 (Georgia World Congress Center)

Eric L Smith, MD, PhD1, Sham Mailankody, MBBS2*, Arnab Ghosh, MBBS, PhD3*, Reed Masakayan, MS4*, Mette Staehr, PhD5*, Terence J Purdon, MS5*, Elizabeth Halton, NP5*, Claudia Diamonte, RN5*, Pavan Anant5*, Yvette Bernal, MS6*, Xiuyan Wang, PhD7*, Yongzeng Wang, PhD8*, Sarah Garrett9*, Steven Almo, PhD10*, Pei Wang, PhD11*, Hong Liu, MD, PhD12*, Yiyang Xu, PhD11*, Elena Mead, MD13*, Jae H. Park, MD14, Kevin J. Curran, MD3, Craig S. Sauter, MD15, Sergio A. Giralt, MD16, Ola Landgren, MD, PhD17, Ahmet Dogan, MD, PhD18, Mikhail Roshal, MD PhD18, Cheng Liu, PhD11*, Isabelle Riviere, PhD7* and Renier J. Brentjens, MD, PhD19

1Department of Medicine, Myeloma Service, Memorial Sloan-Kettering Cancer Center/New York Presbyterian, New York, NY
2MSKCC, New York, NY
3Memorial Sloan-Kettering Cancer Center, New York, NY
4Agenus Inc, Lexington, MA
5Memorial Sloan Kettering Cancer Center, New York, NY
6Memorial Sloan Kettering Cncer Center, New York
7Cell Therapy and Cell Engineering Facility, Memorial Sloan Kettering Cancer Center, New York, NY
8Memorial Sloan kettering Cancer Center, New York, NY
9Albert Einstein College of Medicine, bronx, NY
10Albert Einstein College of Medicine, Bronx, NY
11Eureka Therapeutics, Inc., Emeryville, CA
12Eureka Therapeutics, Inc., Everyville, CA
13Anesthesiology-Critical Care, Memorial Sloan Kettering Cancer Center, New York, NY
14Leukemia Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
15Adult Bone Marrow Transplant Service, Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
16Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
17Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY
18Hematopathology Service, Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY
19Department of Medicine, Leukemia Service, Memorial Sloan Kettering Cancer Center, New York, NY

Patients with relapsed/refractory MM (RRMM) rarely obtain durable remissions with available therapies. Clinical use of BCMA targeted CAR T cell therapy was first reported in 12/2015 for RRMM, and based on small numbers, preliminary results appear promising. Given that host immune anti-murine CAR responses have limited the efficacy of repeat dosing (Turtle C. Sci Trans Med 2016), our goal was to develop a human BCMA targeted CAR T cell vector for clinical translation.

We screened a human B cell derived scFv phage display library containing 6x1010 scFvs with BCMA expressing NIH 3T3 cells, and validated results on human MM cell lines. 57 unique and diverse BCMA specific scFvs were identified containing light and heavy chain CDR’s each covering 6 subfamilies, with HCDR3 length ranges from 5-18 amino acids. 17 scFvs met stringent specificity criteria, and a diverse set was cloned into CAR vectors with either a CD28 or a 4-1BB co-stimulatory domain. Donor T cells transduced with BCMA targeted CAR vectors that conveyed particularly desirable properties over multiple in vitro assays, including: cytotoxicity on human MM cell lines at low E:T ratios (>90% lysis, 1:1, 16h), robust proliferation after repeat antigen stimulation (up to 700 fold, stimulation q3-4d for 14d), and active cytokine profiling, were selected for in vivo studies using a marrow predominant human MM cell line model in NSG mice. A single IV injection of CAR T cells, either early (4d) or late (21d) after MM engraftment was evaluated. In both cases survival was increased when treated with BCMA targeted CAR T cells vs CD19 targeted CAR T cells (median OS at 60d NR vs 35d p<0.05). Tumor and CAR T cells were imaged in vivo by taking advantage of luciferase constructs with different substrates. Results show rapid tumor clearance, peak (>10,000 fold) CAR T expansion at day 6, followed by contraction of CAR T cells after MM clearance, confirming the efficacy of the anti-BCMA scFv/4-1BB containing construct.

Co-culture with primary cells from a range of normal tissues did not activate CAR T cells as noted by a lack of IFN release. Co-culture of 293 cells expressing this scFv with those expressing a library of other TNFRSF or Ig receptor members demonstrated specific binding to BCMA. GLP toxicity studies in mice showed no unexpected adverse events. We generated a retroviral construct for clinical use including a truncated epithelial growth factor receptor (EGFRt) elimination gene: EGFRt/hBCMA-41BBz.

Clinical investigation of this construct is underway in a dose escalation, single institution trial. Enrollment is completed on 2/4 planned dose levels (DL). On DL1 pts received cyclophosphamide conditioning (3g/m2 x1) and 72x106 mean CAR+ T cells. On DL2 pts received lower dose cyclophosphamide/fludarabine (300/30 mg/m2 x3) and 137x106 mean CAR+ T cells. All pts screened for BCMA expression by IHC were eligible. High risk cytogenetics were present in 4/6 pts. Median prior lines of therapy was 7; all pts had IMiD, PI, high dose melphalan, and CD38 directed therapies. With a data cut off of 7/20/17, 6 pts are evaluable for safety. There were no DLT’s. At DL1, grade 1 CRS, not requiring intervention, occurred in 1/3 pts. At DL2, grade 1/2 CRS occurred in 2/3 pts; both received IL6R directed Tocilizumab (Toci) with near immediate resolution. In these 2 pts time to onset of fever was a mean 2d, Tmax was 39.4-41.1 C, peak CRP was 25-27mg/dl, peak IL6 level pre and post Toci were 558-632 and 3375-9071 pg/ml, respectively. Additional serum cytokines increased >10 fold from baseline in both pts include: IFNg, GM CSF, Fractalkine, IL5, IL8, and IP10. Increases in ferritin were limited, and there were no cases of hypofibrinogenemia. There were no grade 3-5 CRS and no neurotoxicities or cerebral edema. No pts received steroids or Cetuximab. Median time to count recovery after neutropenia was 10d (range 6-15d).

Objective responses by IMWG criteria after a single dose of CAR T cells were observed across both DLs. At DL1, of 3 pts, responses were 1 VGPR, 1 SD, and 1 pt treated with baseline Mspike 0.46, thus not evaluable by IMWG criteria, had >50% reduction in Mspike, and normalization of K/L ratio. At DL2, 2/2 pts had objective responses with 1 PR and 1 VGPR (baseline 95% marrow involvement); 1 pt is too early to evaluate. As we are employing a human CAR, the study was designed to allow for an optional second dose in pts that do not reach CR. We have treated 2 pts with a second dose, and longer follow up data is pending.

Disclosures: Smith: Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: BCMA targeted CAR T cells, Research Funding. Almo: Cue Biopharma: Other: Founder, head of SABequity holder; Institute for Protein Innovation: Consultancy; AKIN GUMP STRAUSS HAUER & FELD LLP: Consultancy. Wang: Eureka Therapeutics Inc.: Employment, Equity Ownership. Xu: Eureka Therapeutics, Inc: Employment, Equity Ownership. Park: Amgen: Consultancy. Curran: Juno Therapeutics: Research Funding; Novartis: Consultancy. Landgren: International Myeloma Foundation: Research Funding; Multiple Myeloma Research Foundation: Research Funding; Novartis: Honoraria; Merck: Honoraria; Janssen: Honoraria; BMS: Honoraria; Celgene: Honoraria; AMGEN: Honoraria; Vivolux: Research Funding; Glenmark: Research Funding; AMGEN: Research Funding; Celgene: Research Funding; Janssen: Research Funding; National Cancer Institute: Research Funding; FDA: Research Funding; Takeda: Research Funding; Takeda: Honoraria; Celectis: Honoraria. Dogan: Celgene: Consultancy; Peer Review Institute: Consultancy; Roche Pharmaceuticals: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Liu: Eureka Therpeutics Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Brentjens: Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

*signifies non-member of ASH