Characterization of 405B8H3(D‐E), a newly engineered high affinity chimeric LAG‐3 antibody with potent antitumor activity

Abstract

Lymphocyte activation gene-3 (LAG-3) is a type I transmembrane protein with structural similarities to CD4. Overexpression of LAG-3 enables cancer cells to escape immune surveillance, while its blockade reinvigorates exhausted T cells and strengthens anti-infection immunity. Blockade of LAG-3 may have antitumor effects. Here, we generated a novel anti-LAG-3 chimeric antibody, 405B8H3(D-E), through hybridoma technology from monoclonal antibodies produced in mice. The heavy-chain variable region of the selected mouse antibody was grafted onto a human IgG4 scaffold, while a modified light-chain variable region was coupled to the human kappa light-chain constant region. 405B8H3(D-E) could effectively bind LAG-3-expressing HEK293 cells. Moreover, it could bind cynomolgus monkey (cyno) LAG-3 expressed on HEK293 cells with a higher affinity than the reference anti-LAG-3 antibody BMS-986016. Furthermore, 405B8H3(D-E) promoted interleukin-2 secretion and was able to block the interactions of LAG-3 with liver sinusoidal endothelial cell lectin and major histocompatibility complex II molecules. Finally, 405B8H3(D-E) combined with anti-mPD-1-antibody showed effective therapeutic potential in the MC38 tumor mouse model. Therefore, 405B8H3(D-E) is likely to be a promising candidate therapeutic antibody for immunotherapy. Triebel et al.[1] first discovered lymphocyte activation gene-3 (LAG-3) among molecules differentially expressed in interleukin-2 (IL-2)-dependent natural killer cells (NK). LAG-3 is composed of 525 amino acids, with four Ig-like domains, termed domain 1 (D1) to domain 4 (D4). The D1 region contains a proline-rich ring structure, which specifically binds to major histocompatibility complex II (MHC-II) molecules [2]. Like CD4, LAG-3 binds the MHC-II on antigen-presenting cells, but with a much stronger affinity, which effectively inhibit T-cell activation [2]. LAG-3 is expressed on CD4+ and CD8+ T cells,