Preclinical evaluation of [(58m)Co]Co-DOTA-PSMA-617 for Auger electron therapy of prostate cancer

Prostate-specific membrane antigen (PSMA), highly expressed in prostate cancer, is a promising target for radionuclide therapy. Auger electron-emitting radionuclides are well suited for targeted radionuclide therapy if they can be delivered close to the DNA of the targeted cells. This preclinical study evaluated the theranostic pair [(55/58m)Co]Co-DOTA-PSMA-617 for PET imaging and Auger electron therapy of prostate cancer. [(58m)Co]Co-DOTA-PSMA-617 was successfully prepared with > 99% radiochemical yield and purity. In vitro, uptake and subcellular distribution assays in PSMA-positive prostate cancer cells showed PSMA-specific uptake with high cell-associated activity in the nucleus. Incubation with [(58m)Co]Co-DOTA-PSMA-617 reduced cell viability and clonogenic survival in a significant dose-dependent manner (p < 0.05). Biodistribution of xenografted mice showed high specific tumor uptake of the cobalt-labeled PSMA ligand for all time points with rapid clearance from normal tissues, which PET imaging confirmed. In vivo, therapy with [(58m)Co]Co-DOTA-PSMA-617 in tumor-bearing mice demonstrated significantly increased median survival for treated mice compared to control animals (p = 0.0014). In conclusion, [(55/58m)Co]Co-DOTA-PSMA-617 displayed excellent in vitro and in vivo properties, offering significant survival benefits in mice with no observed toxicities.