Synthesis and evaluation of 68Ga-labeled ODAP-PSMA targeting probe / 中华核医学与分子影像杂志

ABSTRACT

Objective:To synthesize a 68Ga-labeled oxalyldiaminopropionic acid (ODAP)-urea based prostate specific membrane antigen (PSMA) targeting probe, and evaluate its properties in vitro and in vivo. Methods:Ligand P151 was synthesized by solid-phase synthesis and its Ki value was determined. The ligand P151 was added into the mixture of 68GaCl 3 and NaOAc solution and was reacted at 95 ℃ for 10 min. The labeling yield and in vitro stability of 68Ga-P151 were determined by high performance liquid chromatography (HPLC). The lipid-water partition coefficient (log P) and cell binding ability were determined. The biodistribution of 68Ga-P151 in normal KM mice was determined. MicroPET imaging of 68Ga-P151 was carried out in prostate cancer 22Rv1 tumor-bearing mice and compared with 68Ga-PSMA 617. Independent sample t test was used to analyze the data. Results:P151 was successfully synthesized with the Ki of 0.58 nmol/L, the labeling yield more than 95% and the radiochemical purity more than 95%. After placement in saline or human serum albumin (HSA) solution at 37 ℃ for 2 h, the radiochemical purity of 68Ga-P151 was still more than 95%, indicating a good stability in vitro. The lipid-water partition coefficient (log P) of 68Ga-P151 was -2.65±0.17, indicating a good hydrophilicity. 68Ga-P151 specifically bound to PSMA in prostate cancer LNCaP cells with the uptake value of (0.83±0.04) percentage injection activity (%IA)/10 5 cells. Biodistribution of normal mice showed that 68Ga-P151 was mainly excreted through kidneys and other organs showed low uptake. MicroPET imaging of tumor-bearing mice showed the maximum standardized uptake value (SUV max 0.79±0.23 vs 0.54±0.05; t=2.12), tumor/kidney ratio (2.04±0.65 vs 1.88±0.33; t=0.44) and tumor/muscle ratio (12.83±5.18 vs 6.95±1.63; t=2.17) between 68Ga-P151 and 68Ga-PSMA 617 were not significantly different (all P>0.05). Conclusions:68Ga-P151 can be prepared simply and labeled in high yield and show improved pharmacokinetic properties in vivo. The imaging of 68Ga-P151 on PSMA positive tumor is comparable to that of 68Ga-PSMA 617, making it a potential radiopharmaceutical for the diagnosis of prostate cancer.