Preparation, formulation and quality control of one step kit 99m Tc - EDDA/HYNIC-Tyr3-Octreotide as a peptide radiopharmaceutical for imaging somatostatin receptor positive tumors

The high expression of somatostatin receptors in many tumours, have made receptor scintigraphy with 11In-DTPA-Octreotide a widely used procedure in nuclear medicine. Despite its clinical success, some limitation and drawbacks of radiolabelling with 11In remain, especially those concerned with the cost, availability and physical decay properties of this radionuclide. 99m Tc - EDDA/HYNIC-Tyr3-Octreotide was studied as a new agent with the potential to replace octreoscan in somatostatin receptor scintigraphy. This hydrazino nicotinic acid derivatized somatostatin complex contains ethylenediamine N, N diacetic acid as a co-ligand resulting in a high in vitro and in vivo stability. High labeling yields (>90%) were achieved at high specific activities. Characterization via HPLC, biodistribution and receptor binding of the resulting complex are described. The formulation developed enables rapid and simple labeling of 99m Tc - EDDA/HYNIC-TOC in a manner suitable for clinical setting