TC-99M LABELING OF THE IOR CEA-1 MONOCLONAL-ANTIBODY - EVALUATION OF DIFFERENT METHODS

Aim: The aim of this study was to investigate the in vivo and in vitro properties of Tc-99m labelled monoclonal antibody, IOR CEA 1 when rad iolabelled by different methods. Methods: To achieve that purpose IOR CEA was directly radiolabelled via 2-mercaptoethanol (2-Me) and stanno us ion (SnCl2) reduction and indirectly via the 2-iminothiolane (2-lm) conjugation. The resulting Tc-99m-MoAbs were analysed for number of f ree sulfhydryl groups, chemical and radiochemical purity (checked by H PLC and SDS PAGE), immunoreactivity and biological distribution rn mic e. Results: Experimental results indicated a similar radiochemical pur ity and immunoreactivity for direct labelling methods and a decrease o f both for 2-lm method. 2-Me antibody reduction led to a high antibody fragmentation as indicated by non-denaturing SDS PAGE analysis. Never theless SnCl2 and 2-lm labels revealed lower in vivo stability. Conclu sion: Tc-99m-(2-Me) IOR CEA presented favorable in vitro and in vivo p roperties. Therefore this label was compared to Tc-99m-monoclonal anti body BW 431/26. Similar characteristics were found. Clinical studies a lso revealed identical biodistribution profile.