Preparation and Preliminary Biological Evaluation of 177Lu Labelled Rituximab

For evaluating whether 177Lu-Rituximab could be applied for radioimmunoimaging and radioimmunotherrapy of non-Hodgkin’s Lymphoma， Rituximab, a specific chimeric monoclonal antibody used in CD20-positive B-cell Non-Hodgkin’s Lymphoma, was conjugated to bifunctional chelating agents (CHX-A''-DTPA and p-SCN-Bz-DTPA) and radiolabelled with 177Lu successively. 177Lu-CHX-A''-DTPA-Rituximab and 177Lu-p-SCN-Bz-DTPA-Rituximab were obtained with labelling yield and radiochemical purity higher than 99% at optimized conditions, and showed good in vitro stability in different testing system at room temperature and 37 ℃. However, the results of biodistribution in normal mice showed high uptakes in bone which indicated that 177Lu released from the radiolabelled antibodies. The retention of free 177Lu in the bone was lower for 177Lu-p-SCN-Bz-DTPA-Rituximab compared with 177Lu-CHX-A''-DTPA-Rituximab. Our preliminary work demonstrated that p-SCN-Bz-DTPA may be more suitable for 177Lu labelling of monoclonal antibodies