The radioactive Pd and Pd palladium bipyridyl-bisphosphonate complexes for radionuclide therapy of bone metastatic tumor cells.

Two radioisotopes of palladium, Pd and Pd, are considered promising candidates for therapeutic applications because they emit Auger electrons, which are known for their effectiveness in targeting and destroying cancerous cells. We synthesized complexes of Pd and Pd with two bipyridyl and one alendronate molecule. The complexes demonstrated stability and a strong affinity for the surface of hydroxyapatite grains, the main mineral component of bones. Radioactive complexes show significantly higher cytotoxicity against human prostate (DU 145) and ovarian Her2 positive (SKOV-3) cancer cell lines compared to trastuzumab labeled with the Auger electron emitter I and cisplatin. The biological studies showed that both Pd, a pure Auger electron emitter, and Pd, which emits both beta and Auger electrons, demonstrate high cytotoxicity. Furthermore, it was observed that in the tested complexes, Ag, a decay product of Pd, was released from the complex following the decay of Pd. In contrast, Rh, a decay product of Pd, remained within the structure of the complex. The release of Rh from the Pd complex is inhibited by the presence of delocalized electrons in the aromatic bipyridyl ligand. The concept of using a Pd/Ag and Pd/Rh generator encourages further exploration of this treatment strategy.