SLAMF7 is highly expressed in multiple myeloma (MM), but also in subsets of normal T, B, and NK cells. Gogishvili et al. engineered SLAMF7-CAR T cells from both healthy donors and MM patients that effectively targeted newly diagnosed and relapsed/refractory myeloma in vitro and demonstrated complete resolution of MM manifestations after a single dose in a murine xenograft model (although MM eventually reemerged from anatomical sanctuaries). Subsets of normal B, T, and NK cells that were SLAMF7-/low were spared from fratricide and remained functional.

SLAMF7 is under intense investigation as a target for immunotherapy in multiple myeloma. Here, we redirected the specificity of T-cells to SLAMF7 through expression of a chimeric antigen receptor (CAR) derived from the huLuc63 antibody (Elotuzumab), and demonstrate that SLAMF7-CAR T-cells prepared from patients and healthy donors confer potent antimyeloma reactivity. We confirmed uniform, high-level expression of SLAMF7 on malignant plasma cells in previously untreated and in relapsed/refractory (R/R) myeloma patients who had received prior treatment with proteasome-inhibitors and immunomodulatory agents (IMiDs). Consequently, SLAMF7-CAR T-cells conferred rapid cytolysis of previously untreated and R/R primary myeloma cells in vitro Further, a single administration of SLAMF7-CAR T-cells led to resolution of medullary and extramedullary myeloma manifestations in a murine xenograft model in vivo SLAMF7 is expressed on a fraction of normal lymphocytes, including subsets of NK-cells, T-cells and B-cells. Following modification with the SLAMF7-CAR, both CD8+ and CD4+ T-cells rapidly acquired and maintained a SLAMF7- phenotype, and could be readily expanded to therapeutically relevant cell doses. We analyzed recognition of normal lymophocytes by SLAMF7-CAR T-cells and show that they induce selective fratricide of SLAMF7+/high NK-cells, CD4+ and CD8+ T-cells and B-cells. Importantly however, the fratricide conferred by SLAMF7-CAR T-cells spares the SLAMF7-/low fraction in each cell subset and preserves functional lymphocytes, including virus-specific T-cells. In aggregate, our data illustrate the potential to utilize SLAMF7-CAR T-cell therapy as an effective treatment against multiple myeloma and provide novel insights into the consequences of targeting SLAMF7 for the normal lymphocyte compartment.

Author Info: (1) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (2) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (3) Medizi

Author Info: (1) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (2) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (3) Medizinische Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (4) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (5) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (6) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (7) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany. (8) Medizinische Klinik und Poliklinik II, Universitaetsklinikum Wuerzburg, Germany; hudecek_m@ukw.de.