Preparation and evaluation of new bifunctional chelating agents: a preliminary report

A scheme has been designed to synthesize a homologous series of new bifunctional chelating agents (BFCAs), which may increase the thermodynamic stability of metal chelates and conjugate at the specific sites on the monoclonal antibody molecule (MoAb) permitting us to analyze the structure-activity relationships of the series of compounds. Four such compounds have been prepared and characterized by FT-i.r. and NMR spectroscopy. One of them has been used to label an antibody with 111In, the stability and distribution of which has been examined in tumor-bearing mice and compared to that of the 111In-MoAb prepared using cyclic anhydride of DTPA. Enhanced tumor/blood ratios (9 vs 6.5), tumour to muscle ratios (7 vs 3), and decreased liver uptake (4 vs 12%) have been obtained.