This booklet discusses Darzalex® and Darzalex Faspro® -- two different formulations of an equally effective monoclonal antibody that target the CD38 protein on the surface of myeloma cells. This targeted therapy enlists the cells of the immune system to help attack and kill myeloma cells. CD38 is found in very high amounts on the surface of myeloma cells but only in very low amounts on healthy cells in the bone marrow. This medication mostly attacks the cancer, making it easier for healthy cells to recover after treatment.