High-yield synthesis of the terminal 188Re(N) multiple bond from generator-produced [188ReO4]-

A novel procedure for the high-yield preparation of Re-188 radiopharmaceuticals containing a terminal Re(N) multiple bond is described. This method involves the reaction of [188ReO4]- with N-methyl S-methyl dithiocarbazate, as donor of nitrido nitrogen atoms, sodium oxalate and SnCl2 to afford a mixture of two intermediate compounds. When this mixture is reacted with the sodium salt of a dithiocarbamate ligand (L), the formation of the bis-substituted neutral complexes [188Re(N)(L)2] is easily obtained in high yield (95%). The complexes [188Re(N)(L)2] were characterised by chromatographic methods and by comparison with the corresponding complexes prepared at macroscopic level starting from a non-radioactive rhenium precursor. Biodistribution studies were carried out in rats. Results showed that the complexes [188Re(N)(L)2] exhibited the same biological behaviour of the analogous Tc-99m complexes reported previously. The easy application of the new synthetic procedure indicates that it could be conveniently employed for preparing a large class of new Re-188 complexes having potential utilisation in Nuclear Medicine as therapeutic agents