Opdivo 40 mg injection OPDIVO contains nivolumab, a human immunoglobulin G4 (IgG4) monoclonal antibody that acts as an immune checkpoint inhibitor by targeting the programmed death-1 (PD-1) receptor. Under physiological conditions, PD-1 signaling suppresses T-cell activity to prevent autoimmune toxicity. Tumors often exploit this pathway by expressing PD-1 ligands (PD-L1 and PD-L2) to evade immune destruction. Nivolumab selectively binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, relieving PD-1 pathway-mediated suppression of T-cell proliferation and cytokine secretion. This restored T-cell activity enhances anti-tumor immune responses. OPDIVO is indicated for the treatment of various malignancies, including advanced melanoma, non-small cell lung cancer (NSCLC), renal cell carcinoma (RCC), classical Hodgkin lymphoma, squamous cell carcinoma of the head and neck, urothelial carcinoma, MSI-H/dMMR metastatic colorectal cancer, hepatocellular carcinoma, esophageal cancer, and gastric cancer.