This is a humanized IgG4 antibody using the same sequences as the therapeutic antibody relatlimab. It reacts with human LAG3, also known as CD223. Lymphocyte-activation protein 3 belongs to Ig superfamily and contains 4 extracellular Ig-like domains. LAG3 shares approximately 20% amino acid sequence homology with CD4, but has similar structure and binds to MHC class II with higher affinity, providing negative regulation of T cell receptor signaling. LAG3 has been shown to promotes immune responses by activating antigen-presenting cells, and relatlimab is an LAG3 inhibitor. A combination of relatlimab with the immunomodulatory drug lenalidomide significantly increases IL2 production by T cells and antibody-dependent cytotoxicity mediated by NK cells. In humans, antibody-mediated down‑regulation of LAG3 and PD1 allows more effective control of chronic malaria.