A drug used to treat multiple myeloma. It is used with dexamethasone and lenalidomide or bortezomib in patients whose cancer was treated with at least one anticancer therapy. It is used alone in patients whose cancer was treated with at least three anticancer therapies, including a proteasome inhibitor and an immunomodulating agent. It is also being studied in the treatment of other types of cancer. Darzalex binds to a protein called CD38, which is found on some types of immune cells and cancer cells, including myeloma cells. Darzalex may block CD38 and help the immune system kill cancer cells. It is a type of monoclonal antibody. Also called daratumumab.