Darzalex (daratumumab) is a targeted monoclonal antibody used to treat multiple myeloma, a cancer that affects plasma cells in the bone marrow, in adults. Darzalex is given as an intravenous (IV) infusion over several hours, and Darzalex Faspro is given as an injection under the skin (subcutaneous injection) over 3 to 5 minutes. darzalex injection price