ABSTRACT
Lymphocyte activation gene-3 (LAG-3, CD223) is a class of immunosuppressive receptors, mainly expressed on the cell surface of activated T and natural killer (NK) cells. As with programmed death-1 (PD-1), T cell immunoglobulin domain and mucin domain-3 (TIM-3) and other immune check-points, the expression of LAG-3 in activated T cells is upregulated to prevent the occurrence of autoimmune diseases. In the tumor microenvironment, persistent antigenic stimulation can induce T cells to overexpress LAG-3 and other suppressor molecules, causing local immune suppression in the tumor microenvironment. However, the mechanism by which LAG-3 inhibits downstream signals of T-activation or interacts with other immunosuppressive molecules is still unknown. Preliminary clinical data has shown that anti-LAG-3 and anti-PD-1 antibodies possess synergistic effect on the treatment of tumors. Moreover, LAG-3 has different intracellular domains which are completely different from those of any other immunological negative regulatory molecules, suggesting that LAG-3 might have a unique molecular mechanism and prospect of application. Currently, there are at least 7 kinds of antibody drugs targeting LAG-3 and one kind of LAG-3-Fc fusion protein in clinical research, which indicates that anti-LAG-3 targeted drugs have a broad prospect of clinical application.