Synthesis and preliminary evaluation of a new chelate N2S4 for use in labeling proteins with metallic radionuclides.

The successful attachment of various metallic radionuclides such as 99mTc to monoclonal antibodies for targeting tumor tissue in vivo depends upon the development and use of suitable bifunctional chelating agents. We have successfully synthesized a new N2S4 (compound 4) chelate. This chelate forms a stable complex with 99mTc and is capable of coupling to different proteins. The N2S4 compound is quite stable if kept as a hydrochloride salt and is coupled to antibody under neutral conditions with better than 95% efficiency without the loss of immunoreactivity.