Definition

A fully humanized, Fc-engineered monoclonal antibody with masked antigen-binding regions directed against the human T-cell-expressed receptor cytotoxic T-lymphocyte-associated antigen 4 (CTLA4; CTLA-4), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration and the activation of the antigen-binding regions via cleavage by proteases that are upregulated in the tumor microenvironment (TME), anti-CTLA-4 monoclonal antibody XTX101 targets and binds to CTLA-4 expressed on T cells and inhibits the CTLA-4-mediated downregulation of T-cell activation. This leads to a cytotoxic T-lymphocyte (CTL)-mediated immune response against cancer cells, thereby killing cancer cells. CTLA-4, an inhibitory receptor and member of the immunoglobulin superfamily (IgSF), plays a key role in the downregulation of the immune system.