New Immunotherapy Treatment Darzalex for Multiple Myeloma Cancer1 Darzalex (daratumumab) is a recent FDA approved immunotherapy for the treatment of multiple myeloma cancer. In this video, Dr. Stephen Lemon, a medical oncologist, talks about how this immunotherapy treatment works, including what types of side effects it may cause. Visit to watch more new cancer treatments from Dr. Lemon. Darzalex is developed by Janssen Biotech. Stephen Lemon MD is a medical oncologist who is not affiliated with Janssen Biotech.