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

Rituximab was successively labeled with [Ga-67]-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 degrees C using DOTA, N-hydroxy succinimide (NHS) in CH2Cl2. DOTA-Rituximab was obtained by the addition of I mL of a Rituximab pharmaceutical solution (5 mg/mL, in phosphate buffer, pH = 7.8) to a glass tube pre-coated with DOTA-NHS (0.0 1 -0.1 mg) at 25 degrees C with continuous mild stirring for 15 h. Radiolabeling was performed at 37 degrees 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 Ga-67-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 mu m filter. Preliminary biodistribution studies in normal rat model performed to determine complex distribution of the radioimmunoconjugate up to 28 h.