Synthesis, quality control and biological evaluation of tris[(1,10-phenanthroline)[¹⁵³Sm]samarium(III)]trithiocyanate complex as a therapeutic agent

Abstract

Therapeutic radiopharmaceuticals are designed to deliver high doses of radiation to selected target organs or tissues with an aim of minimizing unwanted radiation to surrounding healthy tissue. In this work, [tris(1,10-phenanthroline) [¹⁵³Sm]samarium(III)]trithiocyanate (¹⁵³Sm-TPTTC) was developed for possible therapeutic properties. The cold compound, i.e.^natSm-TPTTC was prepared and characterized by IR, UV, mass and ¹H-NMR spectroscopy. ¹⁵³Sm-TPTTC was prepared in two steps using [¹⁵³Sm]SmCl₃, obtained by neutron activation of an enriched ¹⁵²Sm sample. Stability tests, partition coefficient determination, toxicity tests and biodistribution studies of the complex in wild-type and fibrosarcoma-bearing mice were determined. The radiolabeled complex was prepared in high radiochemical purity (> 99% precipitation method) and specific activity of 278 GBq/mmol and demonstrated significant stability at 4, 25 and 37 ºC (in presence of human serum). Initial complex biodistribution data showed significant liver accumulation in wild-type mice and significant tumor accumulation in fibrosarcoma-bearing mice with tumor:blood and tumor:muscle ratios of 3.55 (2 h) and 38.26 (96 h) respectively. ¹⁵³Sm-TPTTC properties suggest an efficient tumor targeting agent with high tumor-avidity. Further investigation on the therapeutic properties must be conducted.