Development of a Marrow Transplant Regimen for Acute Leukemia Using Targeted Hematopoietic Irradiation Delivered by I3lI-Labeled Anti-CD45 Antibody, Combined With Cyclophosphamide and Total Body Irradiation

In an attempt t o decrease the relapse rate after bone marrow transplantation (BMT) for advanced acute leukemia, we initiated studies using '3'1-labeled anti-CD45 antibody (BC81 to deliver radiation specifically t o hematopoietic tissues, followed by a standard transplant preparative regimen. Biodistribution studies were performed in 23 patients using 0.5 mg/kg trace '3'1-labeled BC8 antibody. The BC8 antibody was cleared rapidly from plasma with an initial disappearance half-time of 1.5 f 0.2 hours, presumably reflecting rapid antigen-specific binding. The mean radiation absorbed doses (cGy/mCi l3lI administered) were as follows: marrow, 7.1 +0.8; spleen, 10.8 f 1.4; liver, 2.7 f 0.2; lungs, 2.1 C 0.1; kidneys, 0.7 f 0.1; and total body, 0.4 f 0.03. Patients with acute myelogenous leukemia (AML) in relapse had a higher marrow dose (11.4 cGy/mCi) than those in remission (5.2 cGy/mCi; P = .001) because of higher uptake and longer