The US biopharmaceutical company, Actinium Pharmaceuticals Inc., has announced it is starting a Phase I trial of its drug Actimab-M for relapsed and/or refractory myeloma patients. Actimab-M is the anti-CD33 antibody, HuM-195, conjugated to the radioactive compound actinium 225 and has been used in other haematological malignancies including acute myeloid leukaemia. Studies show that CD33 is expressed in 25 – 35% of myeloma patients and appears to be more evident in the heavily pretreated group. The Phase I trial is an open label, dose-escalation study designed to assess the safety and efficacy of Actimab-M in relapsed and/or refractory patients who have had at least three previous lines of treatment or who are refractory to QUAD treatment (carfilzomib, lenalidomide, pomalidomide and dexamethasone). The trial is being conducted initially in the United States of America.