J Nucl Med. 2007; 48 (Supplement 2):73P
Radiopharmaceutical Chemistry: Radiopharmacy
Radiopharmacology/Radiometals/Pharmacy Practice |
Labelling of different DOTA-derivatised peptides with 68Ga applying fully automated synthesis
Clemens Decristoforo1,
Roger Knopp2,
Marco Rupprich1,
Elisabeth von Guggenberg1,
Michael Gabriel1,
Irene Virgolini1 and
Roland Haubner1
1 Department of Nuclear Medicine, Medizinische Universität Innsbruck, Innsbruck, Austria;
2 Eckert & Ziegler Eurotope GmbH, Berlin, Germany
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Objectives: PET imaging of tumours using 68Ga-labelled peptides has shown clinical usefulness for a number of applications. A variety of peptides have been suggested for imaging neuroendocrine tumours including DOTA-TOC, DOTA-TATE, DOTA-NOC and DOTA-Lanreotide. We have developed a fully automated system for preparation of 68Ga-labelled peptides. Here we describe the comparison of labelling of a variety of DOTA-dervatised peptides. Methods: A commercially available 68Ga-Generator (Cyclotron Co Ltd, Obninsk, Russia) was eluted with 0.1N HCl. A fully automated system allowing fractionated elution, peptide labelling and final SPE-purification was developed. Reaction parameters such as buffer conditions, pH-range, reaction temperature and time, volumes of reaction solution and generator fraction were initially optimized for labelling DOTA-TOC and applied for DOTA-TATE, DOTA-NOC, DOTA-RGD, DOTA-Minigastrin and DOTA-Lanreotide. Breakthrough of 68Ge and final 68Ge content as well as overall reaction yields, pH, sterility and endotoxins were determined. Results: The decsribed system allows fully automated labelling of DOTA-derivatised peptides in quantitative yields by adding 10-50 nmol of peptide and 1 N Acetate solution (pH 3.6-4.0) and heating for 5 min at 95°C. The RP-SPE-purification, necessary to reduce the amount of 68Ge below 100 Bq/ml, resulted in variable activity retention up to 20% on the SPE cartridge. Final yields of 68Ga- DOTA-derivatised peptides varied between 35 and 55% of total 68Ga-activity (not decay corrected, overall synthesis time: 12min), mainly dependent on cartridge retention. Conclusions: The described system allowed the fully automated preparation of a variety of 68Ga-DOTA-derivatised peptides in very short times in amounts suitable for clinical application. Moreover it has been used successfully and reliably for routine preparations of 68Ga-DOTA-TOC in clinical studies.
