Synthesis and 99(m)Tc-labelling of bz-MAG3-triprolinyl-peptides, their radiochemical evaluation and in vitro receptor-binding

Here we describe a convenient and general solid-phase synthetic method to p repare bifunctional peptides for efficient complexation with Tc-99m. This a pproach permits the reproducible, efficient, and convenient preparation of very pure (typically >90%) peptide-chelator-radiometal complexes by incorpo rating a triproline (P-3) spacer between a benzoyl-protected mercaptoacetyl triglycine (bz-MAG3) bifunctional chelating agent (BFCA) and the targeting peptide. Synthesis and radiochemical evaluation of a number of different bz -MAG3-P-3-peptide conjugates show that they can be efficiently labeled with Tc-99m under mild conditions, can bind to their cellular targets, are resi stant to cysteine challenge, and show good stability in plasma.