@article {Jeong830, author = {Jae Min Jeong and Mee Kyung Hong and Young Soo Chang and Yun-Sang Lee and Young Joo Kim and Gi Jeong Cheon and Dong Soo Lee and June-Key Chung and Myung Chul Lee}, title = {Preparation of a Promising Angiogenesis PET Imaging Agent: 68Ga-Labeled c(RGDyK){\textendash}Isothiocyanatobenzyl-1,4,7-Triazacyclononane-1,4,7-Triacetic Acid and Feasibility Studies in Mice}, volume = {49}, number = {5}, pages = {830--836}, year = {2008}, doi = {10.2967/jnumed.107.047423}, publisher = {Society of Nuclear Medicine}, abstract = {Arg-Gly-Asp (RGD) derivatives have been labeled with various radioisotopes for the imaging of angiogenesis in ischemic tissue, in which αvβ3 integrin plays an important role. In this study, cyclic Arg-Gly-Asp-d-Tyr-Lys [c(RGDyK)] was conjugated with 2-(p-isothiocyanatobenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (SCN-Bz-NOTA) and then labeled with 68Ga. The labeled RGD so produced was subjected to an in vitro binding assay and in vivo biodistribution and PET studies. Methods: A mixture of SCN-Bz-NOTA (660 nmol) and c(RGDyK) (600 nmol) in 0.1 M sodium carbonate buffer (pH 9.5) was allowed to react for 20 h at room temperature in the dark for thiourea bond formation. The conjugate obtained was purified by semipreparative high-performance liquid chromatography (HPLC). The purified c(RGDyK){\textendash}SCN-Bz-NOTA (NOTA-RGD) was then labeled with 68Ga from a 68Ge/68Ga generator and purified by semipreparative HPLC. A competitive binding assay for c(RGDyK) and NOTA-RGD was performed with 125I-c(RGDyK) as a radioligand and αvβ3 integrin{\textendash}coated plates as a solid phase. 68Ga-NOTA-RGD (0.222 MBq/100 μL) was injected, through a tail vein, into mice with hind limb ischemia and into mice bearing human colon cancer SNU-C4 xenografts. Biodistribution and imaging studies were performed at 1 and 2 h after injection. Results: The labeling of NOTA-RGD with 68Ga was straightforward. The Ki values of c(RGDyK) and NOTA-RGD were 1.3 and 1.9 nM, respectively. In the biodistribution study, the mean {\textpm} SD uptake of 68Ga-NOTA-RGD by ischemic muscles was 1.6 {\textpm} 0.2 percentage injected dose per gram (\%ID/g); this uptake was significantly blocked by cold c(RGDyK) to 0.6 {\textpm} 0.3 \%ID/g (P \< 0.01). Tumor uptake was 5.1 {\textpm} 1.0 \%ID/g, and the tumor-to-blood ratio was 10.3 {\textpm} 4.8. Small-animal PET revealed rapid excretion through the urine and high levels of tumor and kidney uptake. Conclusion: Stable 68Ga-NOTA-RGD was obtained in a straightforward manner at a high yield and showed a high affinity for αvβ3 integrin, specific uptake by angiogenic muscles, a high level of uptake by tumors, and rapid renal excretion. 68Ga-NOTA-RGD was found to be a promising radioligand for the imaging of angiogenesis.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/49/5/830}, eprint = {https://jnm.snmjournals.org/content/49/5/830.full.pdf}, journal = {Journal of Nuclear Medicine} }