Introduction: Peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogues has become an established method of treatment of disseminated neuroendocrine tumor (NET). Recent advances in somatostatin analogues have paved the way to the development of octreotate, which can be labeled with both 177Lu and 90Y radionuclide and is characterized by a higher affinity for somatostatin receptor type 2 leading to high tumor uptake. 90Y emits beta particles with a high maximum energy (Emax 2.27 MeV) and long maximum particle range in tissues (10 mm), whereas 177Lu has lower energy (Emax 0.497 MeV) and a shorter particle range in tissues (maximum 2–4 mm).

Objetive: The aim of this work was to establish the labeling and the quality control procedures of 90Y-Tyr3-octreotate, using DOTA (1,4,7,10-tetrazacyclododecane-N,N´,N”,N´”-tetra acetic acid) as chelating agent.

Material and methods: The labelling of DOTATATE (Pichem) with 90-Ytrium (90YCl3, Perkin Elmer) was based in previously described procedures. The labelling was performed at pH 4.5 with 555 – 1,850MBq of 90YCl3 in sodium acetate buffer at 85oC for 25 minutes using peptide: radionuclide ratios of 1 - 2 ug / 3.7MBq). Manual procedures and an automatic synthesis module were used. The stability of the final product was evaluated up to 24 hours under refrigeration. The radiochemical purity was determined by TLC-SG in 0.1M sodium citrate, pH 5.5, as solvent. The labeled peptide migrates from the origin Rf = 0.1–0.2 and the radionuclide migrates with the solvent front Rf = 1.0. Radiochemical purity was also determined using Sep-Pak, C18. The free radionuclide was eluted with 5 mL of 0.1M buffer acetate pH 5.5 and the labeled peptide with 5 mL of methanol.

Results: The labeling conditions, in a manual procedure with a relation of 37MBq/2ug of peptide, at 85 oC for 25 minutes, presented a radiochemical purity of (99.66±0.22)% and (99.07±1.07)%, at 1 and 24h after labeling, respectively (n = 5), meanwhile, no significant difference in the radiochemical purity was observed using the automatic synthesis module from Eckert & Ziegler, (99.60±0.21)% and (99.5±0.47)%, at 1 and 24h after labeling, respectively (n = 3).

Conclusion: The labeling and quality control procedures have been developed at the Radiopharmacy Directory of IPEN– CNEN/SP and it is under validation process. Further studies will be performed in order to provide high quality peptide radiopharmaceuticals for clinical use for PRRT in Brazil.