A comparative distribution study of 111In-labeled DTPA and TTHA monoclonal antibody conjugates in a choriocarcinoma xenograft model

Abstract

Conjugates of the chelating agents DTPA and TTHA with a monoclonal anti-HCG were prepared. The tissue distribution of the 111In-labeled conjugates and also 111In-citrate was studied in mice bearing human choriocarcinoma xenografts. The antibody conjugates both gave high liver and spleen radionuclide accumulation. Elevated femur levels were observed for the TTHA conjugate and 111In-citrate. Generally the DTPA conjugate showed the highest tumor/tissue ratios, although its tumor/blood ratio was lower than the other two materials. The results infer that the DTPA conjugate has the greatest utility as an imaging agent but that it would require a background subtraction technique.