A now well established approach to cancer immunotherapy is using antibodies that are directed against substance (antigen) on a cancer cell surface. A monoclonal antibody is a molecule that attaches to the cancer cell and causes changes within it or in immune cells around it, or it can carry a toxin or a radioactive material to the cancer cell. A fully human monoclonal antibody directed against the human cell surface receptor PD-1 (programmed death-1 or programmed cell death-1/PCD-1) it activates the immune T cells and induces cell-mediated immune responses against tumor. These antibodies can restore the immune efforts to kill cancer cells or to inhibit their growth. First use in humans was published by Berger et al in 2008 and showed that a single administration is safe and well tolerated in patients with advanced hematologic malignancies. A more recent report in 2012 in the prestigious New England Journal of Medicine in 296 patients found cumulative response rates (all doses) of 18% among patients with non–small-cell lung cancer (14 of 76 patients), 28% among patients with melanoma (26 of 94 patients), and 27% among patients with renal-cell cancer (9 of 33 patients). On the other hand, Grade 3 or 4 drug-related adverse events occurred in 14% of patients; there were three deaths from pulmonary toxicity. Ongoing studies should bring more clarity to how this agent can contribute to treating cancer.
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