 Pembrolizumab MK-3475 is a humanized monoclonal antibody. An antibody is a common type of protein made in the body in response to a foreign substance. Antibodies attack foreign substances and protect against infection. Antibodies can also be produced in the laboratory for use in treating patients, an antibody that is made in the lab is also known as a humanized monoclonal antibody. There are now several approved antibodies for the therapy of cancer and other disease. Pembrolizumab MK-3475 has been studied in lab experiments and in other types of cancer. Information from these studies suggests that Pembrolizumab MK-3475 may be beneficial in your type of cancer. 