Study on the Solution for the Reduced [68Ga]Ga-PSMA-11 Synthesis Yield

Abstract

[68Ga]Ga-PSMA-11 is a prostate-specific membrane antigen (PSMA)-targeting radiopharmaceutical based on lysine-urea-glutamic acid derivatives. This study aimed to identify the cause of the irregular decrease in the radiosynthesis yield of [68Ga]Ga-PSMA-11 and to suggest a solution. An irregular decrease in production yield occurred during the synthesis of [68Ga]Ga-PSMA-11 using a cassette-based automatic synthesizer. Although the reagents used in synthesizing [68Ga]Ga-PSMA-11 were replaced with new products, the irregular decrease in radiosynthesis yield continued. In addition, cassettes, equipment, and operating programs used in the cassette-based automatic synthesizer operated normally. On the other hand, when eluting with 0.6 N hydrochloric acid(HCl), leakage was found at the outlet line connection site of the 68Ge/68Ga generator. The 68Ge/68Ga generator was eluted with 0.6 N HCl two to four hours before synthesis to remove impurities and improve the synthetic yield reduction. No further irregular yield reduction occurred after using this method. In the event of an irregular decrease in the radiolabeling yield, the pretreatment method developed in this study would help produce [68Ga]Ga-PSMA-11 injections with a stable labeling yield.