Role of 99mTc in the Development of Rhenium Radiopharmaceuticals. Chapter 16

Due to the chemical analogy between rhenium and technetium, some potentially valuable therapeutic 188Re and 186Re radiopharmaceuticals have come about through prior experience with 99mTc. These include the pentavalent Re(V)-DMSA complex and labelling methods for biomolecules such as cysteine containing peptide sequences and MAG3 for labelling with the Re(V)oxo core, and polyhistidine sequences for labelling with the Re(I)tricarbonyl core. However, emerging rhenium radiopharmaceuticals often show significant differences from their technetium counterparts in terms of preparation methods, and the structure, stability and biological behaviour of the products. Exceptions are the DMSA and tricarbonyl complexes which appear to be highly analogous in structure and oxidation state, if not in preparation. Many currently investigated rhenium radiopharmaceuticals are particulate in nature and in these instances technetium chemistry has little to contribute to their development. Despite the differences, the similarity between rhenium and technetium has been a useful guide in radiopharmaceutical development. (author)