Overcoming antigen loss in CAR T therapy with Vγ9Vδ2 CAR T-cells.

BACKGROUND: Vγ9Vδ2 T-cells demonstrate potent antitumor activity in vitro but, despite successful safety studies, the clinical benefit of Vγ9Vδ2 in adoptive cell therapy has been limited. One approach to enhance the therapeutic potential of Vγ9Vδ2 T-cells while maintaining their safety profile is genetic engineering to express a chimeric antigen receptor (CAR). Vγ9Vδ2 CAR T-cells retain the ability to target tumor cells even after target antigen loss, a major cause of CAR treatment relapse. METHODS: Vγ9Vδ2 T-cells were expanded from peripheral blood mononuclear cells in the presence of high levels of interleukin 2 (IL-2) or IL-2 in combination with IL-15. Cells were then virally transduced with a CD19-directed CAR and underwent antigen-specific stimulation to enrich CAR-expressing cells. RESULTS: Vγ9Vδ2 CAR T-cells showed similar cytotoxic activity to conventional αβ-CAR T-cells against CD19-positive tumor cells. They demonstrated superior responses against CD19-negative tumor cells, however, particularly when IL-15 was included during expansion. This enhanced function was further confirmed in co-culture assays with mixed CD19-positive and CD19-negative tumor populations, simulating antigen loss. CONCLUSIONS: Vγ9Vδ2 CAR T-cell therapy presents a promising strategy for B-cell malignancies, offering sustained antitumor activity even after antigen loss. This approach may help overcome a major limitation of conventional CAR T-cell therapy, potentially improving clinical outcomes.