Labeling of DOTA-Tyr3-octreotate with 177Lu - stability and biodistribution study

ABSTRACT

The labeling with 177Lu and quality control procedures to produced DOTA (1,4,7,10-N,N´,N´´,N´´´, tetraazaciclododecane tetraacetic acid) coupled octreotate labeled peptide was evaluated. The labeling was performed using 30µg of DOTA-Tyr3-octreotate and 500 and 1110 MBq of 177Lu, buffered with sodium acetate/acetic acid 0.4M pH 4.5 for 20 minutes at 100ºC. The radiochemical purity was determined by ITLC na HPLC. Biological distribution studies were performed on Nude mices with tumours (AR42J rat pancreatic tumour cells) by invasive method. The stability of the 177Lu-DOTA-Tyr3-octreotate was followed by 7 days, and in both labeling procedures, the radiochemical purity were superior than 98 percent. Biodistribution studies showed fast blood clearance and the kidneys were the critical organs. The uptake in tumour were significant after 24 hours and the labeled peptide showed high in vivo stability.