Radiolabeling and physicochemical characterization of terbium-161 DOTATATE

To standardize the in-house radiolabeling procedure of [161Tb]Tb-DOTATATE and to assess its physicochemical characteristics to facilitate the clinical application of somatostatin receptor-targeted radionuclide therapy.

[161Tb]Tb-DOTATATE was prepared by reconstituting DOTATATE in sodium acetate buffer (pH 4.5), along with ascorbic acid as a radio-stabilizer. The mixture was then incubated for 1 h at 100 °C. The radiochemical yield and radiochemical purity (RCP) of the final product were determined using radio-thin-layer chromatography (TLC) and radio-HPLC. Radionuclide identification was confirmed by high-purity germanium (HPGe) spectroscopy. In addition, the labeled product partition coefficient (log Po/w) and in-vitro plasma protein binding (PPB) were also tested. The in-vitro stability of the product was studied in saline and human serum using instant thin layer chromatography (ITLC) methods for up to 7 days.

Heating time affected the radiolabeling yield, which was greater than 99% at 1 h and 40% at 30 min in a dry bath. The RCP obtained was greater than 99% as measured by the radio TLC scanner using the ITLC method. HPGe spectroscopy confirmed the radionuclide identity. The radiolabeled product exhibits good hydrophilicity, acceptable PPB, and stable in-vitro behavior in both saline and human serum for up to 7 days.

The radiolabeling protocol produced high-quality, reproducible [161Tb]Tb-DOTATATE with excellent physicochemical properties. This validates the feasibility of in-house production of [161Tb]Tb-DOTATATE and provides a basis for future preclinical and clinical research into its therapeutic potential.