Copper-67-labeled monoclonal antibody Lym-1, a potential radiopharmaceutical for cancer therapy: Labeling and biodistribution in RAJI tumored mice

Copper-67 (⁶⁷Cu) is one of the most compromising radiometals for radioimmunotherapy because of its 61.5 hr physical half-life, abundant beta particles, and gamma emmissions suitable for imaging. However, ⁶⁷Cu is readily tranferred from the usual chelates of EDTA or DTPA to albumen. We developed a new macrocycle (6-p-nitrobenzyl-TETA) to chelate copper. Bifunctional chelating agent p-bromoacetamidobenzyl-TETA was conjugated to Lym-1, a monoclonal antibody against human B cell lymphoma, without significantly altering its immunoreactivity. This conjugate was stably labeled with ⁶⁷Cu under conditions chosen to optimize the yield of a high specific activity radiopharmaceutical. The biodistribution in RAJI tumor bearing mice demonstrated significant tumor uptake (14.7% ID per gram) and extended residence time (120 hr) in contrast to normal organs. After 24 hr, radioactivity was continuously cleared from all tissues except the tumor. This study suggests ⁶⁷Cu labeled Lym-1 to be a promising radiopharmaceutical for potential use for radioimmunotherapy of B cell lymphoma.