Definition

A monoclonal antibody targeting the co-inhibitory receptor lymphocyte-activation gene 3 protein (LAG-3; LAG3; CD223), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, anti-LAG-3 monoclonal antibody LBL-007 targets and binds to LAG-3 expressed by tumor infiltrating lymphocytes (TILs) and blocks the interaction between LAG-3 and major histocompatibility complex class II (MHC II) molecules on the surface of antigen-presenting cells (APCs) and tumor cells. This prevents the negative regulation of T-cell activity that occurs via LAG-3-MHC II binding and enhances a cytotoxic T-lymphocyte (CTL)-mediated immune response against tumor cells, leading to a reduction in tumor growth. LAG-3, a member of the immunoglobulin superfamily (IgSF), negatively regulates both the proliferation and activation of T cells. Its expression on TILs is associated with tumor-mediated immune suppression.