The work is aimed at finding an effective way to acquire radiolabeled antibody with excellent in vivo stability. N–Succinimidyl 3–iodo[125I]benzoate(S125IB) was obtained from radioiodination of N–Succinimidyl 3–(tri-n-butylstannyl) benzoate(ATE) . and S125IB was conjugated to Hepama–1. The radioiodination condition was optimized and the stability and biological activity in vitro of 125IBA-Hepama–1 was evaluated. Animal biodistribution studies were carried out. The labeling ratio of radioiodination of ATE using N-chlorosuccinimide(NCS) was more than 98%

and the conjugation efficiency of S125IB and Hepama–1 was up to 90%

with good stability and biological activity. The localization of radioactivity observed in thyroids of mice decreased obviously. The results show that indirect radiolabeling procedure with ATE is an excellent and efficient way for radiohalogenation of Hepama-1 and other proteins or peptides.