Used in cancer immunotherapy to enhance the body's immune response against tumor cells by blocking the PD-1 receptor on T-cells. This inhibition prevents cancer cells from evading immune detection, allowing T-cells to recognize and destroy tumors more effectively. Investigated in clinical trials for various cancers, including melanoma, non-small cell lung cancer, and hematologic malignancies. Shows potential in combination therapies with other immune checkpoint inhibitors or conventional treatments like chemotherapy and radiation.