Effective alpha-particle-mediated radioimmunotherapy of murine leukemia

The specificity, toxicity, and efficacy of alpha-particle-mediated radioimmunotherapy of murine erythroleukemia was assessed by use of tumor-specific monoclonal antibody 103A labeled with 212Bi. Forty % of the injected dose/g tissue targeted to neoplastic spleens within 1 h after i.v. injection. When 212Bi-103A was injected on day 13 of disease, a dose-dependent response was achieved, as measured by a reduction in splenomegaly and absence of liver metastasis. Mice treated with 212Bi-103A on day 8 of disease showed no histological evidence of erythroleukemia on day 22 and survived significantly longer (median, 118 days) than mice treated with 212Bi-control IgG (78 days) or untreated mice (63 days), indicating successful specific radioimmunotherapy.