Samarium-153-(4-[((bis (phosphonomethyl)) carbamoyl) methyl]-7,10-bis (carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid: A novel agent for bone pain palliation therapy

Abstract

Various phosphonate ligands labeled with β--emitting radionuclides have shown good efficacy for bone pain palliation. In this study, a new agent for bone pain palliation has been developed. Samarium-153-(4-[((bis(phosphonomethyl))carbamoyl)methyl]-7,10-bis (carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid (153Sm-BPAMD) complex was prepared using BPAMD ligand and samarium-153 chloride. The effect of various parameters on the labeling yield of 153Sm-BPAMD including ligand concentration, pH, temperature, and reaction time were studied. Production of 153Sm was performed at a research reactor using 152Sm (n, γ)153Sm nuclear reaction. The radiochemical purity of the radiolabeled complex was checked by instant thin layer chromatography. Stability studies of the complex in the final preparation and the presence of human serum were performed up to 48 h. Partition coefficient and hydroxyapatite (HA) binding of the complex were investigated and biodistribution studies using single photon emission computed tomography (SPECT) and scarification were performed after injection of the complex to wild-type mice. 153Sm-BPAMD was prepared in a high radiochemical purity >98% and specific activity of 267 GBq/mmol at the optimal conditions. The complex demonstrated significant stability at the room temperature and in human serum at least for 48 h. HA binding assay demonstrated that at the amount of more than 5 mg, approximately, all radiolabeled complex was bind to HA. At the pH 7.4, log Po/w was - 1.86 ± 0.02. Both SPECT and scarification showed major accumulation of the labeled compound in the bone tissue. The results show that 153Sm-BPAMD has interesting characteristics as an agent for bone pain palliation, however, further biological studies in other mammals are still needed.