Darzalex 400mg injection is a targeted therapy for cancer containing the active ingredient Daratumumab, which belongs to the group of medicine called monoclonal antibodies. Monoclonal antibodies are proteins that recognize and attach to the specific target, killing the cancer cells. It is used to treat a type of cancer called multiple myeloma (bone marrow cancer) in adults 18 years or older. Report to your doctor if you have ever had a hepatitis B infection; this medicine may cause the hepatitis B virus to become active again. This medicine can decrease platelets (helps in blood clotting) and white blood cell counts (helps fight infections).