Abstract
The π-clamp-mediated conjugation method, which enables site-specific modification of cysteine residues, is a promising strategy for developing well-defined radiolabelled biomolecules for positron emission tomography (PET) imaging. We have applied this method to site-specifically attach the macrocyclic chelators "NODA" and "NODAGA" to the somatostatin receptor 2-targeted peptide, octreotate. The resulting novel NODA-octreotate and NODAGA-octreotate compounds can be radiolabelled with either [(18)F]AlF(-) or [(68)Ga]Ga(3+) respectively. In vivo PET imaging shows that the [(68)Ga]Ga(3+)-labelled derivative exhibits high stability and favourable pharmacokinetic properties.