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502 Universal SLAMF7-Specific CAR T-Cells As Treatment for Multiple Myeloma

Program: Oral and Poster Abstracts
Type: Oral
Session: 652. Myeloma: Pathophysiology and Pre-Clinical Studies, excluding Therapy: Novel Immunotherapeutic Strategies in Multiple Myeloma
Sunday, December 10, 2017: 5:15 PM
Bldg B, Lvl 3, B308-B309 (Georgia World Congress Center)

Rohit Mathur, PhD1*, Zheng Zhang2*, Jin He3*, Roman Galetto, PhD4*, Agnès Gouble, PhD4*, Isabelle Chion-Sotinel4*, Stéphanie Filipe, PhD4*, Annabelle Gariboldi4*, Tanooha Veeramachaneni2*, Elisabet E. Manasanch, MD5, Sheeba K. Thomas, MD6, Hans C. Lee, MD7, Krina K. Patel, MD MSc7, Donna M. Weber, MD7, R. Eric Davis, MD8*, Robert J. Orlowski, MD, PhD9*, Julianne Smith, PhD10, Jing Yang, PhD11 and Sattva S. Neelapu, MD12

1MD ANDERSON CANCER CENTER, HOUSTON, TX
2MD Anderson Cancer Center, Houston, TX
3UT MD Anderson Cancer Center, Houston, TX
4Cellectis SA, Paris, France
5Department of Lymphoma and Myeloma, UT MD Anderson Cancer Center, Houston, TX
6Lymphoma and Myeloma, UT M.D. Anderson Cancer Center, Houston, TX
7Lymphoma and Myeloma, University of Texas MD Anderson Cancer Center, Houston, TX
8Department of Lymphoma and Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX
9Lymphoma/Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX
10Cellectis NY, New York
11M.D. Anderson Cancer Center, Houston, TX
12Department of Lymphoma and Myeloma, MD Anderson Cancer Center, Houston, TX

Introduction: Signaling lymphocytic activation molecule F7 (SLAMF7, also called CS1) is highly expressed on multiple myeloma (MM) tumor cells but has limited expression in a subset of hematopoietic cells among normal tissues, making it a rational target for chimeric antigen receptor (CAR) T-cell therapy in MM. Currently, most CAR-T cell therapy products are generated from autologous T-cells, which is a major limitation logistically and likely difficult to do for lymphopenic and most critically ill patients. Therefore, we have designed allogeneic “off-the-shelf” engineered CAR T-cells (derived from normal healthy donor peripheral blood mononuclear cells), which contain an inactivation of the TCRα constant (TRAC) gene using TALEN® gene-editing technology to prevent graft-versus-host disease. The SLAMF7 gene is also inactivated using TALEN® in order to minimize the risk of fratricide of SLAMF7-specific CAR+ T-cells (Galetto et al, ASH 2015, Abstract 116). Here, we report in vitro and in vivo efficacy results from double knock-out (KO) (TRAC and SLAMF7) SLAMF7-specific universal CAR T-cells (UCARTCS1) against MM cell lines and primary MM tumor cells.

Methods: The function of UCARTCS1 cells was tested in vitro against MM cell line (MM.1S) and primary MM tumor cells using flow-cytometry-based cytotoxicity, degranulation, CFSE proliferation, and multiplex cytokine induction assays. The efficacy of UCARTCS1 was also tested in vivo against primary MM xenografts in human fetal bone implanted into NOD/SCID/IL2rgnull mice (NSG-hu). Double KO (TRAC and SLAMF7) T-cells lacking SLAMF7 CAR served as controls. The potential toxicity of UCARTCS1 against hematopoietic cells has also been assessed in vitro using the cytotoxicity assay.

Results: UCARTCS1, but not control double KO T-cells, specifically lysed MM.1S (median, 93% lysis; range, 78-98% with UCARTCS1 vs. median, 17%; range, 15-47% with control T-cells; n=10 experiments) and primary MM tumor cells (n=10 samples) (median 59%; range, 20-90% with UCARTCS1 vs. median 9%; range, 0-36% with control T cells). In agreement with this, we observed specific degranulation in both CD4+ and CD8+ UCARTCS1 cells but not control T-cells in presence of MM.1S cells and primary MM tumor cells. In addition, significant and specific proliferation of both CD4+ and CD8+ UCARTCS1 cells but not control T-cells was observed when they were co-cultured with MM.1S or primary MM tumor samples (n=8). Analysis of culture supernatants for ten cytokines showed that UCARTCS1 cells primarily produced IFN-γ and GM-CSF in presence of primary MM tumor cells (n=6) suggesting a Th1/Tc1 response. On the other hand, UCARTCS1 did not induce any significant lysis of normal donor peripheral blood mononuclear cells or CD34+ hematopoietic cells from bone marrow aspirates of healthy donors.

To test the efficacy of UCARTCS1 cells in vivo we injected 1x106 CD138-purified primary MM tumor cells into the NSG-hu mouse model. After the tumor had been established (6-8 weeks with a serum M-protein level >15 µg/ml), mice were treated intravenously with a single injection of either 10x106 total cells/mouse of UCARTCS1 or control T-cells. Mice treated with control T-cells developed gradual increase in M-protein levels (median, 339 µg/ml; range, 100-700 µg/mL) whereas the M-protein levels rapidly became undetectable in the mice treated with UCARTCS1 cells and remained undetectable until they were euthanized at approximately 50 days after adoptive transfer.

Conclusion: Our studies revealed that UCARTCS1 cells specifically target and lyse primary MM tumor cells both in vitro and in vivo. Further, UCARTCS1 cells specifically degranulated, produced Th1/Tc1 cytokines, and proliferated in response to primary MM tumor cells. Our results support further development and testing of this universal “off-the-shelf” allogeneic SLAMF7-specific CAR-T product in patients with MM.

Disclosures: Galetto: Cellectis SA: Employment. Gouble: Cellectis SA: Employment. Filipe: Cellectis: Employment. Gariboldi: Cellectis SA: Employment. Thomas: Celgene: Research Funding; Bristol Myers Squibb: Research Funding. Lee: Daiichi Sankyo: Research Funding; Celgene: Consultancy; Takeda: Consultancy. Patel: Juno: Consultancy; Celgene: Consultancy; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding. Smith: Cellectis: Employment. Yang: Poseida Therapuetics: Research Funding; Cellectis: Research Funding. Neelapu: Cellectis Inc.: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karus: Research Funding; Bristol-Myers Squibb: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Poseida Therapeutics, Inc: Research Funding.

*signifies non-member of ASH