99mTc-Markierung des monoklonalen Antikörpers IOR CEA 1: Bewertung unterschiedlicher Methoden

Aim: The aim of this study was to investigate the in vivo and in vitro properties of 99mTc labelled monoclonal antibody, IOR CEA 1 when radio-labelled by different methods. Methods: To achieve that purpose IOR CEA was directly radiolabeled via 2-mercaptoethanol (2-Me) and stannous ion (SnCI2) reduction and indirectly via the 2-iminothiolane (2-lm) conjugation. The resulting 99mTc-MoAbs were analysed for number of free sulfhydryl groups, chemical and radiochemical purity (checked by HPLC and SDS PAGE), immunoreactivity and biological distribution in mice. Results: Experimental results indicated a similar radiochemical purity and immunoreactivity for direct labelling methods and a decrease of both for 2-lm method. 2-Me antibody reduction led to a high antibody fragmentation as indicated by non-denaturing SDS PAGE analysis. Nevertheless SnCI2 and 2-lm labels revealed lower in vivo stability. Conclusion: 99mTc-(2-Me) IOR CEA presented favorable in vitro and in vivo properties. Therefore this label was compared to 99mTc-monoclonal antibody BW 431/26. Similar characteristics were found. Clinical studies also revealed identical biodistribution profile.