Synthesis and biodistribution of a new oxo-technetium-99m bis(aminothiol) complex as a potential melanoma tracer.

[123I]-N-(2-Diethylaminoethyl)-4-iodobenzamide (123I-BZA) has been the best scintigraphic agent described so far for malignant melanoma and ocular melanoma diagnosis. We replaced 123I by the more convenient radioisotope 99mTc and synthesized four bis(aminoethanethiol) derivatives. We describe the synthesis of a new oxo-technetium complex (TcO-Cf), prepared in very high yield (radiochemical yield > 95%), that exhibits an affinity for the pigmented tumor cells. This complex was evaluated in vivo in mice bearing C57Bl6 murine melanoma. After injection, a rapid decrease in the radioactivity levels was noted for all tissues and organs except for eyes (1.26 %ID/g at 1 h and 2.69 %ID/g at 24 h postinjection) and the tumor (1.19 %ID/g at 1 h and 0.80 %ID/g at 24 h postinjection), suggesting a specific in vivo binding of this complex to the pigmented cells. These results were compared with those already published for three other technetium-99m bis(aminothiol) complexes with benzamide derivatives.