Noninvasive Evaluation of CD20 Expression Using 64Cu-Labeled F(ab')2 Fragments of Obinutuzumab in Lymphoma.

摘要: CD20-overexpressed non-Hodgkin lymphoma typically indicates progressive malignancy. Obinutuzumab is a next-generation Food and Drug Administration-approved humanized monoclonal antibody that targets CD20. Previous studies with 89Zr-labeled obinutuzumab have successfully imaged CD20 in vivo. However, delayed tumor uptake increased radioactive exposure caused by long blood circulation limit its clinical translation. This study aimed to develop 64Cu-labeled F(ab')2 fragments of for imaging xenograft models. Methods: were produced from using an IgG-degrading enzyme Streptococcus pyogenes (IdeS) purified protein A beads. Sodium dodecyl sulfate polyacrylamide gel electrophoresis high-performance liquid chromatography performed evaluate the products their stability. conjugated p-SCN-Bn-NOTA (NOTA) 64Cu radiolabeling. Western blotting was screen expression levels cells. Enzyme-linked immunosorbent assay, flow cytometry, confocal used test binding affinity vitro. Serial PET biodistribution subcutaneous lymphoma-bearing mice 64Cu-NOTA-F(ab')2-obinutuzumab or 64Cu-NOTA-F(ab')2-IgG. Results: F(ab')2-obinutuzumab F(ab')2-IgG IdeS digestion system confirmed sodium chromatography. The radiochemical purity no less than 98%, specific activity 56.3 ± 7.9 MBq/mg (n = 6). Among 5 cell lines, Ramos showed strongest CD20, CLL-155 lowest, as enzyme-linked imaging. revealed rapid sustained tumor-bearing mice. peak (9.08 1.67 percentage injected dose per gram tissue [%ID/g]) model significantly higher CCL-155 (2.78 0.62 %ID/g) 64Cu-NOTA-F(ab')2-IgG control (1.93 0.26 %ID/g, n 4, P < 0.001). tumor-to-blood tumor-to-muscle ratios 7.3 1.6 21.9 9.0, respectively, at 48 h after injection group. Of measured off-target organs, kidneys highest uptake. Ex vivo immunofluorescent staining verified differential Conclusion: demonstrated had CD20-positive high contrast, which could enable noninvasive evaluation clinic.