Preliminary evaluation of synthesis and quality control results for ⁶⁸Ga-labeled exendin using an automated module

To share our experience regarding the synthesis and quality control of generator-based ⁶⁸Ga-labeled exendin using an automated module. A 50 mCi ⁶⁸Ge/ ⁶⁸Ga generator (ITG, Germany) was eluted with 0.05 M HCl. Eluate in the form of gallium chloride was passed through a cation exchange. It removes the impurities and preconcentrates the solution. ⁶⁸GaCl 3 was adsorbed onto the cartridge and rest passed into waste. N2 solution (mixture of acetone, metal-free water, and concentrated HCl) was used to release concentrated and purified ⁶⁸Ga from the strata X-C cartridge, which then reached the reaction vial. This contained the precursor, i.e., exendin dissolved in metal-free water. The reaction vessel was kept at 80°C-85°C temperature for 18 min. It was then cooled and diluted by adding 3 ml of metal-free water. The product was transferred to the tC18 cartridge for purification. From this cartridge, the product was transferred into product vial with the help of pure ethanol. The product was passed through 0.22 µm Millipore filter and diluted by adding 25 ml normal saline in the product vial. All the synthesis steps were carried out in an automated module (Modular Lab, Eckert and Ziegler, Germany). Radiation levels were monitored outside the hot cell using portable radiation survey meter. The total synthesis time was approximately 36 min. Quality control testing (clarity, pH, and radiochemical purity) was performed using visual, pH paper, and thin layer chromatography scanner, respectively. The maximum yield of ⁶⁸Ga-exendin was 19 mCi. The labeled preparation was clear with mean pH around 6.0. ⁶⁸Ga-exendin conjugate was prepared with very high radiochemical purity (99%). The product was stable up to 4 h. Outside the hot cell, radiation level was near to background level during the entire process. We formulated generator-based positron emission tomography radiotracer ⁶⁸Ga-exendin with high radiochemical purity and good stability using automated module. (author)