Imaging Somatostatin Positive Tumors with Tyr3-Octreotate/Octreotide Conjugated to Desferrioxamine B Squaramide Radiolabeled with either Zirconium-89 or Gallium-68

Abstract

Radiolabeled derivatives of Tyr3-octreotide and Tyr3-octreotate, synthetic analogues of the peptide hormone somatostatin, can be used for positron emission tomography (PET) imaging of somatostatin receptor expression in neuroendocrine tumors. In this work, a squaramide ester derivative of desferrioxamine B (H3DFOSq) was used attach either Tyr3-octreotide or Tyr3-octreotate to the metal binding ligand to give H3DFOSq-TIDE and H3DFOSq-TATE. These new peptide-H3DFOSq conjugates form stable complexes with either of the positron-emitting radionuclides gallium-68 (t1/2 = 68 min) or zirconium-89 (t1/2 = 3.3 days). The new complexes were evaluated in an AR42J xenograft model that has endogenous expr..