Definition

A radioimmunoconjugate consisting of the humanized monoclonal antibody lintuzumab conjugated to the alpha-emitting radioisotope actinium Ac 225 with potential antineoplastic activity. The monoclonal antibody moiety of actinium Ac 225 lintuzumab specifically binds to the cell surface antigen CD33 antigen, delivering a cytotoxic dose of alpha radiation to cells expressing CD33. CD33 is a cell surface antigen expressed on normal non-pluripotent hematopoietic stem cells and overexpressed on myeloid leukemia cells.