Rhenium diamino dithiol complexes. III - Lipophilic ligands for endotherapeutic radiopharmaceuticals

The chemistry and physical properties of a series of rhenium diamino dithio l (dadt) complexes are described. Liposolubility was enhanced by N-substitu tion of alkyl chains of C-1-C-14 length on one ligand structure, with longe r chain lengths showing the higher solubility, but with a reduction of radi olabelling yield with (99)m Tc and Re-186. Among the Re-V=O [dadt] complexe s synthesized, we found that 2,2,9,9-tetramethyl-4-N-alkyl-4,7-diaza-1,10-d ecanedithiol (alkyl = C-1-C-10) resulted in stable and lipiodol-soluble com plexes. Biological characteristics of the C-6 ligand labelled with Tc-99m a nd Re-186 were compared, and indicated that the complexes behaved in a simi lar manner in rodents. The dadt ligands in combination with Re-188 or Re-18 6 and fatty acid oils merit further consideration as endotherapeutic radiop harmaceuticals for treatment of hepatoma and metastatic liver cancer.