Preparation Method, Quality Control, and Stability Studies of the Radiopharmaceutical Gallium [68Ga] PSMA-11

ABSTRACT Purpose: Gallium-68-based radiopharmaceuticals are widely employed in Nuclear Medicine for PET/CT imaging, particularly in the diagnosis of prostate cancer. This study focuses on the evaluation of the radiochemical and chemical purity of Gallium [68Ga]PSMA-11, also known as [68Ga]Ga-PSMA-HBED-CC, to determine its shelf-life following the end of synthesis (EOS). Methods: The stability study was carried out in accordance with Chapter 10 of the Good Preparation Guidelines for Radiopharmaceuticals, under both standard and "worst-case" conditions. All analytical methods complied with the specifications of the European Pharmacopoeia Monograph 04/2021:3044 (Ph. Eur.), Gallium (68Ga) PSMA-11 Injection. Results: Under standard conditions, Gallium [68Ga] PSMA-11 maintained a radiochemical purity above the threshold specified by the European Pharmacopoeia (≥ 95%) throughout the entire observation period. The assessment of chemical purity confirms these findings, with total impurities maintained at negligible levels. Under "worst-case" storage conditions, a similar stability pattern was observed for samples stored in syringes and for those stored at 4°C and 40°C. However, for samples stored at -22°C, radiochemical purity dropped significantly below the acceptable limit (approximately 83%) at 3 hours after synthesis. Conclusion: The radiopharmaceutical Gallium [68Ga] PSMA-11 prepared using an automated synthesis module is stable for up to 3 hours after synthesis. No significant differences in stability are observed between storage in glass vials and plastic syringes. While exposure to temperatures up to 40°C or refrigeration at 4°C does not alter the product quality, freezing at -22°C compromises the complex structure and radiochemical purity.