The Feasibility Of Targeted Imaging Of Cu-64-Dota-Rituximab Pet In A Xenograft Model Of Human Lymphoma

1051 Purpose: There are increasing needs for the development of radioconjugates using Rituximab because it can be used for selecting proper patients for Rituximab treatment through imaging and for guiding advanced radioimmunotherapy such as alpha particle. The aim of this study is to investigate the feasibility of targeted imaging of 64Cu-DOTA-rituximab PET in a xenograft model of human lymphoma. Methods: CD20 expression was evaluated by western blot in B-cell non-Hodkins lymphoma cell lines (Jurkat, Daudi, and Raji). DOTA-rituximab was conjugated in optimized conditions. 64Cu was chelated to DOTA-rituximab. The number of chelators on rituximab conjugates was verified using MALDI-TOF MS for comparison of rituximab and DOTA-rituximab. Cell binding and saturation assays was performed and analyzed using GraphPad Prism software. Tumor xenograft models were established in balb/c-nu mice using Raji cells. Animal PET/CT imaging was obtained by INVEON scanner (Siemens) after tail vein injection with pre-dose received 2 mg cold rituximab prior to imaging, and without pre-dose.Results: CD20 protein was highly expressed in Daudi and Raji cells. Radiochemical purity of 64Cu-DOTA-rituximab was more than 95%. Binding to jurkat cells was not specific, whereas Daudi and Raji cells was blocked with an excess of cold rituximab, which evaluating the specificity of binding. Saturation assay showed the difference between Daudi (Bmax; 52.8 ± 3.2, and Kd; 30.2 ± 4.4) and Raji (Bmax; 73.0 ± 0.4, and Kd; 32.6 ± 0.4) cells. In PET/CT imaging, binding of 64Cu-DOTA-rituximab was shown in tumors without pre-dose injection group. On the other hand, there was no signal in tumors with pre-dose injection group. Conclusion: We demonstrated that 64Cu-DOTA-rituximab was specifically bound to CD20 positive cell lines, and targeted imaging was feasible in a xenograft model of human lymphoma.