Rejection-resistant off-the-shelf T cells for adoptive cell therapy

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Abstract ‘Off-the-shelf’ (OTS) chimeric antigen receptor (CAR) T cells pre-manufactured from healthy donors are a readily available and less expensive alternative to autologous products. However, immune rejection of OTS cells by host T- and NK-cells may limit their persistence and reduce therapeutic effect. Here, we engineered rejection-resistant OTS T cells that recognize and eliminate alloreactive lymphocytes while retaining desired anti-tumor activity. As T- and NK-cells transiently upregulate 4-1BB after activation, T cells expressing a 4-1BB-specific alloimmune defense receptor (ADR) selectively eliminated activated T- and NK-cells while sparing resting lymphocytes. Using this mechanism, ADR-expressing T cells suppressed alloimmune activation and resisted rejection in a mixed lymphocyte reaction (MLR) model in vitro. Further, T cells co-expressing the ADR and a CD19 CAR retained undiminished activity through both receptors in vitro and in vivo. We established a mouse model of allogeneic cell therapy in which NSG mice were engrafted with systemic CD19+ leukemia and normal human T cells. In this model, adoptively transferred unmodified CD19 CAR T cells from an HLA mismatched donor produced only transient anti-tumor activity and were rapidly rejected by pre-engrafted alloreactive T cells within 7 days, leading to fatal leukemia relapse. In contrast, T cells co-expressing both CAR and ADR were protected from immune rejection, resulting in long-term persistence (>9 weeks) and durable leukemia eradication in most animals. These data support the feasibility of using ADR to generate highly potent OTS CAR T cell products that suppress immune rejection to produce long-term therapeutic benefit even in immunocompetent patients.