Definition

A monoclonal antibody directed against the inhibitory receptor lymphocyte activation gene-3 protein (LAG-3; LAG3; CD223), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, fianlimab binds to LAG-3 expressed by tumor infiltrating lymphocytes (TILs) and blocks LAG-3 binding to tumor cells expressing major histocompatibility complex (MHC) class II molecules. This may activate antigen-specific T lymphocytes and enhance cytotoxic T-lymphocyte (CTL)-mediated tumor cell lysis, which leads to a reduction in tumor growth. LAG-3, a member of the immunoglobulin superfamily (IgSF), is expressed on various immune cells; its expression on TILs is associated with tumor-mediated immune suppression and the negative regulation of both cellular proliferation and T-cell activation.