Synthesis and evaluation of 76Br labeled compound for tumor diagnosis with PET

^<18>F- fdg是PET诊断肿瘤最有价值的工具，但^<18>F因其半衰期短（110分钟）而受到限制。通常，半衰期长的放射性药物使用方便。目前用于PET诊断的所有正电子发射器都不适合标记抗体。与这些放射性核素相比，^<76> Br和^<64> Cu具有合适的性质（^<76> Br: T_<1/2> = 16.1hr, ^<64> Cu: T_1/2 = 12.7hr），它们可能具有很大的免疫pet潜力。^<76> Br或^<64> Cu标记抗体适用于肿瘤诊断。特别是^<76> Br是^<18 >f或^<123 >i等放射性卤素，适合用于标记以^<18 >f或^<123 >i标记的各种化合物，因此我们希望开发以^<76 >br标记的放射性药物用于PET诊断肿瘤。在本研究中，我们合成了抗cd20单克隆抗体（mAb）， NuB2，标记为^<76> Br或^<64> Cu，并评估了在体内诊断肿瘤的潜力。采用与蛋白质碘化类似的直接溴化法对NuB2进行了^<76 bb0 Br标记。为了标记^<64> Cu，通过与对^<64> Cu具有高亲和力的螯合剂- 1,4,8,11 -四氮杂环十四酸-N， N‘， N’， N'-四乙酸（TETA）反应，制备了稳定的免疫偶联物。为了在小动物体内进行生物分布和肿瘤定位研究，我们制备了^<76> Br或^<64> Cu标记的NuB2，并将其用于CD20+肿瘤的SCID小鼠。我们还在注射放射性标记的NuB2后24小时进行了PET成像研究。^<76> Br-NuB2的放射化学产率约为10%，^<64> Cu-TETA-NuB2的放射化学产率约为90%。肿瘤定位研究结果表明，两种化合物的肿瘤放射性浓度在整个实验过程中稳步增加，^<76> Br-NuB2在2天达到10%剂量/g， ^<64> Cu-TETA-NuB2达到13%剂量/g。PET研究也得到了相同的结果。在本研究中，我们成功制备了PET放射标记单克隆抗体，对CD20+肿瘤具有高亲和力。^<76> Br-NuB2和^<64> Cu-TETA-NuB2向肿瘤高度积聚，PET能清晰显示这些图像，离体研究结果相同。^<76> Br-NuB2的肿瘤摄取低于^<64> Cu-TETA-NuB2似乎是由于脱卤作用。从这些数据来看，使用^<76> Br和^<64> Cu进行免疫pet具有很大的肿瘤诊断潜力。少

^<18>F-FDG is most valuable tool for tumor diagnosis with PET, but ^<18> F is limited to use for its short half-life, 110 minutes. Usually, radiopharmaceuticals with long half-life are convenient to use. All positron emitters, now using for PET diagnosis, don't suit for labeling of antibody. Compared with these radionuclides, ^<76> Br and ^<64> Cu have appropriate properties ( ^<76> Br: T_<1/2> = 16.1hr, ^<64> Cu: T_1/2 = 12.7hr) and they may have great potentials for immuno-PET. ^<76> Br or ^<64> Cu labeled antibody is suitable for tumor diagnosis. Especially, ^<76> Br is a radioactive halogen such as ^<18> F or ^<123> I, and it is suitable for labeling of various compounds developed for labeling with ^<18> F or ^<123> I. So we hoped to develop radiopharmaceuticals labeled with ^<76> Br for tumor diagnosis with PET. In this study, we synthesized anti-CD20 monoclonal antibody (mAb), NuB2, labeled with ^<76> Br or ^<64> Cu, and evaluated potential for in vivo diagnosis of tumor. Direct … More bromination similar with iodination of proteins has been applied for ^<76> Br labeling of NuB2. For labeling with ^<64> Cu, a stable immunoconjugate was prepared by reacting NuB2 with 1, 4, 8, 11-tetraazacyclotetradecan-N, N', N', N'-tetraacetic acid (TETA), a chelator exhibiting high affinity for ^<64> Cu. For in vivo biodistribution and tumor localization studies in small animals, ^<76> Br or ^<64> Cu labeled NuB2 was prepared and administered to SCID mice bearing CD20+ tumor. We also performed imaging study with PET at 24hr after injection of radiolabeled NuB2. Radiochemical yield of ^<76> Br-NuB2 was approximately 10 % and that of ^<64> Cu-TETA-NuB2 was approximately 90 %. The results of tumor localization studies show that the tumor concentration of radioactivity increased steadily throughout the course of experiment for both compounds, and reached to 10 %dose/g for ^<76> Br-NuB2 and 13 %dose/g for ^<64> Cu-TETA-NuB2 at 2 days. Same results were also obtained from PET studies. In this study, we successfully prepared radiolabeled mAbs for PET, exhibiting high affinity for CD20+ tumor. ^<76> Br-NuB2 and ^<64> Cu-TETA-NuB2 were highly accumulated to tumor, and PET could show these images clearly, which were same results with ex vivo studies. Lower tumor uptake of ^<76> Br-NuB2 than that of ^<64> Cu-TETA-NuB2 seems to be owing to dehalogenation. From these data, the use of ^<76> Br and ^<64> Cu for immuno-PET has great potential for tumor diagnosis. Less