Conatumumab (also known as AMG 655) is an investigational fully human monoclonal antibody that was developed as a pro-apoptotic agent for the treatment of cancer. It functions as an agonist antibody, designed to activate a specific death receptor pathway that triggers programmed cell death in tumor cells. Clinical trials evaluated its efficacy, both as a monotherapy and in combination with chemotherapy or other targeted agents, in a range of solid tumors, including colorectal cancer, non-small cell lung cancer (NSCLC), pancreatic cancer, and soft tissue sarcoma. Despite initial promise, its development was ultimately discontinued after pivotal phase III trials failed to meet their primary survival endpoints.