Background CAR-T cell therapies have proven safe and efficacious for hematologic malignancies, but there remains a significant unmet need for effective cell therapy options for solid tumors. CAR-engineered induced pluripotent stem cell (iPSC)-derived effector cells allow for the treatment of cancer as an off-the-shelf allogeneic cell therapy. Gamma delta (γδ) T cells exhibit the cytolytic features of conventional alpha beta (αβ) CD8+ T cells with additional capabilities for innate recognition of tumors. For example, expression of CD16 on γδ T cells can mediate antibody-dependent cellular cytotoxicity (ADCC) against tumors. Here we describe development of an iPSC-derived CAR γδ T cell platform which can target solid tumors through both CAR-mediated recognition and ADCC when combined with a therapeutic antibody.
Methods Primary γδ T cells were enriched and expanded in culture to enable reprogramming to iPSCs by delivery of pluripotency genes. These T cell derived iPSCs (TiPSCs) were used to produce γδ T cells using a proprietary differentiation process. The TiPSC line was engineered with a CAR targeting EGFR and a membrane bound form of IL-15 to enhance T cell persistence. Tumor spheroids were generated from EGFR+Her-2+ SKOV-3 ovarian tumor cells. Cytolysis of spheroids was evaluated using CAR-T cells alone or in combination with anti-HER2 antibody (trastuzumab).
Results Batches of CAR-T cells were generated using a proprietary differentiation process yielding >90% pure CAR+ γδ T cells. The TiPSCs contained the rearranged γδ TCR gene and upon differentiation to T cells, uniformly expressed a Vγ9Vδ2 TCR and expressed high levels of CD16. CAR γδ T cells were effective in killing SKOV-3 spheroids. When cultured with SKOV-3 spheroids in an ADCC assay, CAR γδ T cells exhibited enhanced cytotoxicity in the presence of trastuzumab but not isotype control antibody. Activity of the γδ T cells was not reliant on additional exogenous cytokine due to the engineered form of membrane-associated IL-15.
Conclusions We have demonstrated that iPSC-derived γδ T cells mediate anti-tumor activity in human solid tumor models through multiple pathways. The combination of two modes of tumor recognition (CAR and CD16/antibody) enabled more potent killing of solid tumor spheroids. The ability to manufacture large batches of iPSC derived CAR γδ T cells will enable a true off-the-shelf allogenic cell therapy for solid tumors.
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