Apamistamab is a murine monoclonal antibody that targets CD45, a pan-leukocyte antigen. Its therapeutic application is as a radioimmunoconjugate, specifically Iodine-131 labeled Apamistamab (131I-Apamistamab, developed as Iomab-B). It is designed for conditioning therapy prior to hematopoietic stem cell transplantation in patients with relapsed or refractory acute myeloid leukemia and other hematologic malignancies. The antibody delivers a targeted, high dose of radiation directly to CD45-expressing bone marrow and leukemia cells, thereby ablating the diseased marrow to create space for donor stem cell engraftment, while aiming to spare non-hematopoietic tissues.