Preparation, quality control and biodistribution studies of [67Ga]-DOTA-anti-CD20

Abstract

Rituximab was successively labeled with [ 67 Ga]-gallium chloride. The macrocyclic bifunctional chelating agent, N -succinimidyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA-NHS) was prepared at 25 °C using DOTA, N -hydroxy succinimide (NHS) in CH 2 Cl 2 . DOTA-Rituximab was obtained by the addition of 1 mL of a Rituximab pharmaceutical solution (5 mg/mL, in phosphate buffer, pH=7.8) to a glass tube pre-coated with DOTA-NHS (0.01–0.1 mg) at 25 °C with continuous mild stirring for 15 h. Radiolabeling was performed at 37 °C in 3 h. Radio-thin layer chromatography showed an overall radiochemical purity of 90%–95% at optimized conditions (specific activity = 30 GBq/mg, labeling efficacy; 82%). The final isotonic 67 Ga-DOTA-rituximab complex was checked by gel electrophoresis for radiolysis. Radio-TLC was performed to ensure that only one species was present after filtration through a 0.22 μm filter. Preliminary biodistribution studies in normal rat model performed to determine complex distribution of the radioimmunoconjugate up to 28 h.