Definition

A humanized monoclonal antibody directed against the immune checkpoint protein butyrophilin 1A1 (BTN1A1), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti- BTN1A1 monoclonal antibody hSTC810 targets and binds to the extracellular domain of human BTN1A1, which prevents the formation of the BTN1A1-galectin-9 (Gal9)-programmed cell death protein 1 (PD-1) complex, and inhibits downstream signaling pathways. This may restore immune function through the activation of T cells and T-cell-mediated immune responses against tumor cells. The BTN1A1-Gal9-PD-1 axis suppresses T-cell receptor (TCR) signaling and T-cell activation. BTN1A1 does not bind to PD-1 directly but interacts with PD-1 through Gal9. BTN1A1, a member of the butyrophilin superfamily of immunomodulators, is upregulated in a variety of tumor cell types.