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      T Cells Expressing an Anti-B-Cell Maturation Antigen (BCMA) Chimeric Antigen Receptor with a Fully-Human Heavy-Chain-Only Antigen Recognition Domain Induce Remissions in Patients with Relapsed Multiple Myeloma

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          Abstract

          Chimeric antigen receptor (CAR) T cells expressing B-cell maturation antigen (BCMA) can target and kill multiple myeloma (MM). BCMA was chosen as a target for MM because it is expressed by almost all cases of MM but has a restricted expression pattern on normal cells. CAR antigen-recognition domains made up of monoclonal antibody-derived, single-chain-variable fragments (scFv) are potentially immunogenic. To reduce the risk of recipient immune responses against CAR T cells, we used the sequence of a novel anti-BCMA, fully-human, heavy-chain-only binding domain designated FHVH33. The FHVH33 binding domain sequence was from TeneoBio, Inc. FHVH33 is smaller than a scFv. FHVH33 lacks the light chain, artificial linker sequence, and 2 associated junctions of a scFv, so it is predicted to be less immunogenic than a scFv, especially murine-derived scFvs. We constructed a CAR incorporating FHVH33, CD8α hinge and transmembrane domains, a 4-1BB costimulatory domain, and a CD3ζ T-cell activation domain. The CAR, FHVH33-CD8BBZ, is encoded by a γ-retroviral vector. FHVH33-CD8BBZ-expressing T cells (FHVH-BCMA-T) exhibited a full range of T-cell functions in vitro and eliminated tumors and disseminated malignancy in mice (Lam et al, Blood (ASH abstract) 2017 vol 130: 504).

          We are conducting the first clinical trial of FHVH-BCMA-T. Patients receive conditioning chemotherapy on days -5 to -3 with 300 mg/m2 of cyclophosphamide and 30 mg/m2 of fludarabine followed by infusion of FHVH-BCMA-T on day 0. This dose-escalation trial has 5 planned dose levels (DL). Twelve patients have received FHVH-BCMA-T on 3 DLs, 0.75x106, 1.5x106 and 3x106 CAR+ T cells/kg of bodyweight. Three patients were enrolled on the trial but not treated. The median age of patients enrolled was 63 (range 52-70); patients received a median of 6 lines of anti-myeloma therapy (range 3-10) prior to treatment with FHVH-BCMA-T.

          Ten patients out of 12 patients have achieved objective responses (OR). Five patients have obtained CRs or VGPRs to date. One patient achieved a partial remission (PR) 26 weeks after FHVH-BCMA-T infusion through a continued decrease in a measurable plasmacytoma. Five out of 7 patients who had myeloma with high-risk cytogenetics had an OR (Table). ORs occurred in patients with large soft-tissue plasmacytomas. Loss of BCMA expression on myeloma cells after treatment was documented in 2 patients. Two patients who developed progressive MM after CAR T-cell infusion had evidence of minimal residual disease in bone marrow 1-2 months post infusion of CAR T cells (patients 7,8).

          Eleven out of 12 patients had cytokine release syndrome (CRS); CRS grades ranged from 1-3 (Lee et al. Biol Blood Marrow Transplant 25 (2019) 625-638). The median peak C reactive protein (CRP) of the patients with CRS was 156.3 mg/L. Of 12 patients, 1 received the interleukin-6-receptor antagonist tocilizumab on day +6 to treat grade 3 CRS with hypotension requiring low-dose pressor therapy, grade 2 ejection fraction (EF) decrease and elevation of creatinine kinase (CK). All parameters returned to baseline by day +10. Patient 12 had a grade 3 decrease in EF which resolved by day +29. Two patients had grade 2 neurotoxicity that resolved without intervention: patient 3 had headaches, dysarthria and word-finding difficulties that resolved after 6 days while patient 6 had headaches on day +4. Patient 12 had grade 3 neurotoxicity with confusion on day +2; she was given dexamethasone with improvement in mental status the same day. After attaining a response, patient 6 died from influenza complications 6 weeks after FHVH-BCMA-T infusion.

          A median of 10.6% (range 1.1-46) of bone marrow T cells were CAR+ when assessed 14 days after FHVH-BCMA-T infusion. We assessed blood CAR+ cells by quantitative PCR. The median peak level of CAR+ cells was 76.5 cells/µl (range 3-347 cells/µl) and the median day post-infusion of peak blood CAR+ cell levels was 13 (range 9-14).

          The results from this phase 1 trial demonstrate that FHVH-BCMA-T cells can induce responses at low dose levels. Patients who had no CRS or low-grade CRS achieved objective responses. Toxicity was limited and reversible. Accrual to this trial continues. A maximum tolerated dose has not been determined yet. These results encourage further development of FHVH CAR-T.

          Table

          Disclosures

          Manasanch: Janssen: Honoraria; Sanofi: Honoraria; Takeda: Honoraria; Merck: Research Funding; Skyline Diagnostics: Research Funding; Sanofi: Research Funding; Quest Diagnostics: Research Funding; Celgene: Honoraria. Trinklein:Teneobio, Inc.: Employment, Equity Ownership. Buelow:Teneobio, Inc.: Employment, Equity Ownership. Kochenderfer:Kite and Celgene: Research Funding; Bluebird and CRISPR Therapeutics: Other: received royalties on licensing of his inventions.

          OffLabel Disclosure:

          Cyclophosphamide and fludarabine are used in combination for conditioning chemotherapy prior to CAR T-cell infusion

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          Author and article information

          Journal
          Blood
          American Society of Hematology
          0006-4971
          1528-0020
          November 13 2019
          November 13 2019
          : 134
          : Supplement_1
          : 3230
          Affiliations
          [1 ]Medical Oncology Fellowship, National Institutes of Health Clinical Center, Bethesda, MD
          [2 ]Department of Lymphoma and Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX
          [3 ]Experimental Transplantation and Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD
          [4 ]Department of Laboratory Medicine, National Institutes of Health, Bethesda, MD
          [5 ]Laboratory of Pathology, National Cancer Institute, NIH, Bethesda, MD
          [6 ]Department of Laboratory Medicine, National Cancer Institute, National Institute of Health, Bethesda, MD
          [7 ]Cell Processing Section, Department of Transfusion Medicine, National Institutes of Health, Bethesda, MD
          [8 ]Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda,
          [9 ]Teneobio, Inc., Newark, CA
          [10 ]Teneobio, Inc., Menlo Park, CA
          [11 ]Experimental Transplantation and Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda,
          Article
          10.1182/blood-2019-129088
          c087700e-e6f5-4f13-b244-08d8e02eb363
          © 2019
          History

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