Synthesis of DFO*-pPh-NCS: towards a bifunctional ligand for targeted radionuclide therapy

Targeted radionuclide therapy (TRT) is a promising therapeutic method for patients with tumor metastases and inoperable tumors. To perform TRT, a radiopharmaceutical is needed. This radiopharmaceutical contains a bifunctional chelator, which can form a stable complex with a radionuclide. The complex has to be stable because leaching of the radionuclide is not desirable as this would lead to unwanted damage to healthy cells. The bifunctional chelator is also coupled to a targeting vector, i.e. a biomolecule which directs the radiopharmaceutical to the tumor cells once it is injected into the body. Different types of radionuclides can be used in the radiopharmaceutical. Gamma and positron emitters are used for the imaging of the tumor cells. Beta minus and alpha emitters are used for TRT. In this study, the already existing chelator DFO*-pPh-NCS, which is the bifunctional octadentate derivative of the natural siderophore deferoxamine (DFO), was evaluated for the chelation of the radionuclides 153Sm, 161Tb, 177Lu and 225Ac. Studies for complex formation of this chelator with Zr(IV) and Ga(III) have already been performed, but never with f-block elements.