Chemically Controlled, Immunosuppression-Resistant, Anti-Bcma CAR-T Cells for Treatment of Antibody-Mediated Autoimmunity

Auto-reactive antibody production by plasma cells is the direct cause of many auto-immune diseases. In such cases elimination of plasma cells would ameliorate the disease. Chimeric antigen receptor T (CAR-T) cells with cytotoxicity toward cells expressing B-cell maturation antigen (BCMA) have shown remarkable promise for the treatment of multiple myeloma, a plasma cell neoplasm. Elimination of non-malignant plasma cells is a side-effect of anti-BCMA CAR-T treatment of multiple myeloma, suggesting the use of these anti-BCMA CAR T cells for auto-immune indications. Unfortunately, CAR-T administration requires use of lymphodepletion to achieve efficient cell engraftment, and is often accompanied by cytokine release syndrome (CRS), a potentially life-threatening side-effect.

As lymphodepletion and CRS pose morbidity/mortality risks that are unacceptable for therapy of many auto-immune diseases, we have utilized CRISPR-Cas9 gene editing to develop a controllable CAR-T cell platform that provides for (1) engraftment with non-cytotoxic transient immunosuppression; and (2) small-molecule dependent CAR T-cell expansion. We have implemented this platform using a unique dual targeting approach in which a BCMA CAR transgene is integrated into the TRAC locus, and additional payloads are integrated into a second locus, thus also enabling an allogeneic manufacturing process. Transgene integration occurred in >50% of cells individually with several percent of cells targeted at two loci. TRAC-targeted, anti-BCMA CAR T cells demonstrated CAR-dependent, target-cell-BCMA-dependent cytotoxicity towards both high-BCMA- and low-BCMA-expressing cell lines and in multiple myeloma cells xenografted into NSG mice. Drug-regulation properties and immunosuppression resistance are the subject of ongoing experiments. Anti-BCMA CAR T cells that are chemically controlled, incapable of graft-versus-host disease, and insensitive to immunosuppression may be an attractive treatment option a variety of antibody-mediated auto-immune conditions.