Development of [64Cu]-DOTA-anti-CD20 for targeted therapy

Copper-64 was produced as a by-product of Co-55 via Ni-64(p,n)Cu-64 by 15 MeV proton bombardment of Ni-nat resulting in a thick target yield of 5.31 MBq/mu Ah (143.5 mu Ci/mu Ah) and a radiochemical separation yield of 95% (radionuclide purity > 97% after 25 hours of bombardment). Rituximab was successively labeled with [Cu-64]-CuCl2. N-succinimidyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA-NHS) was prepared at 25 degrees C using DOTA and N-hydroxy succinimide (NHS) in CH2Cl2 followed by the addition of 1 ml of a Rituximab pharmaceutical solution. Radiolabeling was performed at 37 degrees C in 3 hours. Radio thin-layer chromatography showed an overall radiochemical purity of 90-95% at optimized conditions (specific activity=30 GBq/mg, labeling efficacy; 82%) using various chromatography systems. The final isotonic (64)CuDOTA-Rituximab complex was passed through a 0.22 mu m filter and checked by gel electrophoresis for radiolysis control. Stability of the final product was checked in the formulation and in presence of human serum at 37 degrees C.