²¹¹At-OKT10-B10 and Fludarabine Alone or in Combination With Cyclophosphamide and Low-Dose TBI Before Donor Stem Cell Transplant for the Treatment of Newly Diagnosed, Recurrent, or Refractory High-Risk Multiple Myeloma

This phase I trial investigates the side effects and best dose of ²¹¹At-OKT10-B10 when given together with fludarabine, alone or in combination with cyclophosphamide and low-dose total-body irradiation (TBI) before donor stem cell transplant in treating patients with high-risk multiple myeloma that is newly diagnosed, has come back (recurrent), or does not respond to treatment (refractory). ²¹¹At-OKT10-B10 is a monoclonal antibody, called OKT10-B10, linked to a radioactive agent called ²¹¹At. OKT10-B10 attaches to CD38 positive cancer cells in a targeted way and delivers ²¹¹At to kill them. Chemotherapy drugs, such as fludarabine and cyclophosphamide, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Radiation therapy such as TBI uses high energy x-rays to kill cancer cells and shrink tumors. Giving ²¹¹At-OKT10-B10 together with chemotherapy and TBI before a donor stem cell transplant helps kill cancer cells in the body and helps make room in the patient's bone marrow for new blood-forming cells. When the healthy stem cells from a donor are infused into a patient, they may help the patient's bone marrow make more healthy cells and platelets and may help destroy any remaining cancer cells.