A drug used alone or with other drugs to treat adults with multiple myeloma. It is used in patients whose cancer is newly diagnosed and who can or cannot be treated with an autologous stem cell transplant. Daratumumab is also used in patients whose cancer came back or did not get better after treatment with one or more anticancer therapies. It is also being studied in the treatment of other types of cancer. Daratumumab binds to a protein called CD38, which is found on some types of immune cells and cancer cells, including myeloma cells. Daratumumab may block CD38 and help the immune system kill cancer cells. It is a type of monoclonal antibody. Also called Darzalex.