Bispecific anti-CD3 x anti-B7-H3 antibody mediates T cell cytotoxic ability to human melanoma in vitro and in vivo

Inhibition of the B7-H3 immune checkpoint is reported to limit the tumor growth of B7-H3⁺ tumors. In this study, we demonstrated B7-H3 expression in human melanoma cells, including a primary culture and several cell lines. Furthermore, we investigated whether B7-H3 could serve as a target for T cell-mediated immunotherapy against melanoma. The cytotoxic capacity of activated T cells (ATCs) armed with an anti-CD3 x anti-B7-H3 bispecific antibody (B7-H3Bi-Ab) to melanoma cells was measured using a bioluminescent signal through a luciferase reporter on tumor cells. In contrast to unarmed ATCs, B7-H3Bi-Ab-armed ATCs exhibited increased cytotoxicity against melanoma cells at effector/target ratios from 1:1 to 20:1. Moreover, B7-H3Bi-Ab-armed ATCs secreted more interferin-gamma (IFN-γ), accompanied by higher levels of activating marker CD69 and CD25 expression. Infusion of B7-H3Bi-Ab-armed ATCs suppressed melanoma growth in a xenograft mouse model. Taken together, our results indicate that B7-H3Bi-Ab-armed ATCs may be a promising approach to immunotherapy for melanoma patients.