Co-expression of LAG-3 with PD-1 in melanoma TIL in the B16-F10 model, and correlation of blood LAG-3+CD8+ immune cells with decreased immune checkpoint blockade (ICB) efficacy in melanoma patients led to the hypothesis that co-inhibition of these pathways may improve responses over single-agent anti-PD-1 therapy.3–5 Relatlimab is a fully human IgG4 antibody that binds to human LAG-3. Here, LAG3 is linked to melanoma.