|Lintuzumab is a monoclonal antibody directed against CD33, a surface antigen found on myeloid leukemia cells. A modified version of lintuzumab that is conjugated with the chelator satetraxetan to facilitate actinium (225Ac) radiolabelling (a radioimmunotherapeutic) has been developed (see Patent US6670456  and IMGT/mAb-db ID 936). 225Ac emits α particles and is used as these cause less nonspecific cytotoxicity than β particles (i.e. decreased killing of bystander cells). 225Ac has been termed a 'nano-generator' as for each decay producing a high-energy α particle, a series of daughter atoms generate additional α particles, effectively amplifying the radioactive dose at the target site. Lintuzumab is a humanized version of the murine anti-CD33 antibody, M195 .