68Ga-DATATOC: Synthesis and first radiolabeling of a kit-type octreotide derivative

272 Objectives 68Ga-DOTATOC is currently used as standard for diagnostic imaging of NETs and its metastases. Radiolabeling can be performed manually and automated at 95 °C. In order to approach application of 68Ga following a kit-type procedure quite similar to the well-accepted 99mTc-radiopharmaceuticals preparation, a DATA-based chelator (6-Amino-1,4-diazepine-triacetate) was used as it has shown to radiolabel under very mild conditions. Conjugation with TOC may enable radiolabeling of the peptide at room temperature quantitatively. Methods DATATOC was synthesized in a seven step synthesis and coupled with [Tyr3]-octreotide. Radiolabeling with 68Ga, purified with any of the established post-processing procedures was performed manually at room temperature and stability was assessed in human serum. An automated setup was also examined using the Modular-Lab eazy (Eckert & Ziegler, Berlin, Germany). Stability of 68Ga-DATATOC was assessed in human serum. Results Radiolabeling was performed at room temperature. Using N2 solution, NaOAc-buffer for example and 13.3 nmol DATATOC, a RCY of 96.3 ± 1.2 % was obtained within 3 min. The complex stability was tested in human serum over a period of 2 h (Δ = 1.3 %). Automated labeling with 23 nmol precursor achieved quantitative complexation of 68Ga (> 99 %). Conclusions DATATOC can be labeled with 68Ga in a manual or automated setup rapidly at room temperature, offering significant advantages over similar DOTA-based derivatives. Because of quantitative labeling yields, product purification is unnecessary. With the perspective towards a kit-type formulation, the superior characteristics of this new compound pave the way for a new generation of 68Ga radiopharmaceuticals. Based on this promising properties first in vivo PET/CT-studies have been started by the Dresden-Rossendorf group and will be presented seperately.