Relatlimab is a human immunoglobulin G4 monoclonal antibody targeting the Lymphocyte-Activation Gene-3 (LAG-3) receptor, which is the first LAG-3 inhibitor approved for clinical use. It works by blocking the interaction between LAG-3 and its ligands, reducing immunosuppression and promoting T-cell proliferation to induce tumor cell death. In March 2022, the U.S. FDA approved the fixed-dose combination of relatlimab with nivolumab (Opdualag) for the treatment of unresectable or metastatic melanoma in adults and pediatric patients aged 12 and older. This article comprehensively discusses the mechanism of action, clinical trials, and safety of relatlimab, as well as an overview of current immune checkpoint drugs used in melanoma treatment. The combination of relatlimab and nivolumab has shown significant efficacy in improving progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) compared to nivolumab monotherapy, with a manageable safety profile. However, treatment-related adverse events are still common, and long-term data on durability of response is needed. The article also highlights ongoing clinical trials testing relatlimab in other cancer types and the potential for combining multiple immune checkpoint inhibitors.Relatlimab is a human immunoglobulin G4 monoclonal antibody targeting the Lymphocyte-Activation Gene-3 (LAG-3) receptor, which is the first LAG-3 inhibitor approved for clinical use. It works by blocking the interaction between LAG-3 and its ligands, reducing immunosuppression and promoting T-cell proliferation to induce tumor cell death. In March 2022, the U.S. FDA approved the fixed-dose combination of relatlimab with nivolumab (Opdualag) for the treatment of unresectable or metastatic melanoma in adults and pediatric patients aged 12 and older. This article comprehensively discusses the mechanism of action, clinical trials, and safety of relatlimab, as well as an overview of current immune checkpoint drugs used in melanoma treatment. The combination of relatlimab and nivolumab has shown significant efficacy in improving progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) compared to nivolumab monotherapy, with a manageable safety profile. However, treatment-related adverse events are still common, and long-term data on durability of response is needed. The article also highlights ongoing clinical trials testing relatlimab in other cancer types and the potential for combining multiple immune checkpoint inhibitors.