Development and In Vitro Evaluation of [⁶⁴Cu]Cu-NOTA-TP-PSMA, a Novel Radiotheranostic Agent Against Prostate Cancer

Prostate cancer (PCa), particularly in its metastatic form, remains a major clinical challenge due to limited diagnostic and therapeutic options. To address this, we developed a novel radiotheranostic agent, [⁶⁴Cu]Cu-NOTA-TP-PSMA, by conjugating a prostate-specific membrane antigen (PSMA) ligand to a ⁶⁴Cu-radiolabeled terpyridine-platinum (TP) compound previously shown to exert selective cytotoxicity against cancer cells. In this study, the biological performance of [⁶⁴Cu]Cu-NOTA-TP-PSMA was compared with the monomeric analogs [⁶⁴Cu]Cu-NOTA-PSMA and [⁶⁴Cu]Cu-NOTA-TP through in vitro studies in PSMA-positive LNCaP prostate cancer cells and non-malignant HEK-293 cells. [⁶⁴Cu]Cu-NOTA-TP-PSMA showed high stability, PSMA binding affinity and exhibited substantially enhanced uptake, internalization, retention, and nuclear localization in LNCaP cells relative to the monomers, whereas uptake and nuclear accumulation in HEK-293 cells were negligible. Cytotoxicity assays further demonstrated potent and selective activity in LNCaP cells, with EC₅₀ values in the low nanomolar range, and minimal toxicity in HEK-293 cells. Collectively, these results identify [⁶⁴Cu]Cu-NOTA-TP-PSMA as a promising radiotheranostic agent, warranting further in vivo evaluation for prostate cancer imaging and targeted radiotherapy.