Evaluation of carrier added (CA) and no carrier added (NCA) 177Lu radionuclide roles in radiolabeling of peptide groups

The peptides radiolabeled with 177Lu are including a wide range of promising radiopharmaceuticals. The NCA form of 177Lu provides a high specific activity that is required in targeted receptor therapy in order to avoid saturation of the targeted receptors. In this study, the outstanding quality of NCA radionuclides especially in the case of 177Lu was evaluated by comparing with CA radionuclide for radiolabeling of DOTATATE peptide and. The NCA 177Lu and CA 177Lu were obtained by chromatography separation of irradiated 176Yb (enrichment: 96.4%) and irradiation of 176Lu (enrichment: 95%) respectively. Radiolabeling of DOTATE with CA and NCA 177Lu was carried out in the same conditions and time. Then, radiolabeling yield was calculated as a function of some parameters like the Ligand: metal ratio and stability of compound after production. The results showed the superiority of NCA 177Lu with respect to CA 177Lu. Not only the particle ratio showed the advantages of the NCA radionuclide, but also the long-term comparison over a period of 14 days revealed the inferior character of CA.177Lu with regard to the high requirements regarding the specific activity set by radio-immunotherapy.