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.