The Radiolabeling of [161Tb]-PSMA-617 by a Novel Radiolabeling Method and Preclinical Evaluation by In Vitro/In Vivo Methods

BACKGROUND: Prostate cancer (PC) is the most common type of cancer in elderly men, with a positive correlation with age. As resistance to treatment has developed, particularly in the progressive stage of the disease and in the presence of microfocal multiple bone metastases, new generation radionuclide therapies have emerged. Recently, [(161)Tb], a radiolanthanide introduced for treating micrometastatic foci, has shown great promise for treating prostate cancer. RESULTS: In this study, Terbium-161 [(161)Tb]Tb was radiolabeled with prostate-specific membrane antigen (PSMA)-617 ([(161)Tb]-PSMA-617) and the therapeutic efficacy of the radiolabeled compound investigated in vitro and in vivo. [(161)Tb]-PSMA-617 was found to have a radiochemical yield of 97.99 ± 2.01% and was hydrophilic. [(161)Tb]-PSMA-617 was also shown to have good stability, with a radiochemical yield of over 95% up to 72 hours. In vitro, [(161)Tb]-PSMA-617 showed a cytotoxic effect on LNCaP cells but not on PC-3 cells. In vivo, scintigraphy imaging visualized the accumulation of [(161)Tb]-PSMA-617 in the prostate, kidneys, and bladder. CONCLUSIONS: The results suggest that [(161)Tb]-PSMA-617 can be an effective radiolabeled agent for the treatment of PSMA positive foci in prostate cancer.