The Feasibility of ⁶⁴Cu-PSMA I&T PET for Prostate Cancer

The goal of this research was to investigate the feasibility of ⁶⁴Cu labeling in prostate-specific membrane antigen imaging and therapy (PSMA I&T) for PSMA positron emission tomography (PET) imaging and biodistribution evaluation. PSMA I&T was labeled with ⁶⁴Cu, and stability in human and mouse sera was evaluated. Prostate cancer cell lines were used for specific uptake assays (22RV1 for PSMA-positive, PC-3 for -negative). Both PC-3 and 22RV1 cells were transplanted into the left and right thighs in a mouse for PET/computed tomography (CT) imaging. Biodistribution was performed using 22RV1 tumor models. Labeling yield (decay corrected) of ⁶⁴Cu-PSMA I&T was more than 95% compared to the free ⁶⁴Cu peak. The serum stability of ⁶⁴Cu-PSMA I&T was maintained at more than 90% until 60 h. Regarding the specific binding of ⁶⁴Cu-PSMA I&T was 7.5-fold higher to 22RV1 cells than PC-3 cells (p < 0.001). On PET/CT imaging, more specific ⁶⁴Cu-PSMA I&T uptake was observed to 22RV1 tumors than to PC-3 tumors. In the PSMA blocking study using 2-phosphonomethoxypropyl adenine (2-PMPA), the ⁶⁴Cu-PSMA I&T signal significantly decreased in the 22RV1 tumor region. In the biodistribution study, the kidney uptake was the highest among all organs at 2 h (52.6 ± 20.8%ID/g) but sharply decreased at 24 and 48 h. Also, the liver showed similar uptake over time (range, 10-12%ID/g). On the contrary, ⁶⁴Cu-PSMA I&T uptake of the tumors increased with time and peaked at 48 h (5.6 ± 0.1%ID/g). PSMA I&T labeled with ⁶⁴Cu showed the feasibility of the PSMA specific PET imaging through in vitro and in vivo studies. Furthermore, ⁶⁴Cu-PSMA I&T might be considered as the candidate of future clinical trial.