Human PD-L1 inhibitor III is primarily used in the field of cancer immunotherapy. It works by blocking the interaction between PD-L1 on tumor cells and PD-1 on immune cells, thereby enhancing the immune system's ability to attack and destroy cancer cells. This inhibitor is particularly valuable in the treatment of various cancers, including lung cancer, melanoma, and bladder cancer, where PD-L1 expression is often elevated. By inhibiting this pathway, it helps to reverse immune suppression in the tumor microenvironment, promoting a more robust anti-tumor response. Additionally, it is utilized in research settings to study the mechanisms of immune checkpoint blockade and to develop new therapeutic strategies for overcoming immune evasion by cancer cells.