Production, quality control, biodistribution assessment and preliminary dose evaluation of (177)Lu-PDTMP as a possible bone palliative agent.

Objectives: In this study, production, quality control, and biodistribution studies of a newly developed therapeutic compound have been presented and are followed by dosimetric evaluation for use in humans based on biodistribution data in wild-type rats.

Materials And Methods: The Lu-1,2-propylene di-amino tetramethylenephosphonic acid (Lu-PDTMP) complex was prepared successfully using synthesized PDTMP ligand and LuCl3. LuCl3 was obtained by thermal neutron irradiation (4×10 n/cm/s) of enriched Lu2O3 samples. The radiochemical purity of Lu-PDTMP was checked by instant thin-layer chromatography. Stability studies of the complex in the final preparation and in the presence of human serum were performed for up to 72 h. The biodistribution of Lu-PDTMP and LuCl3 in wild-type rats was checked in animal tissues for up to 7 days. The absorbed dose of each human organ was calculated by means of the medical internal radiation dose method.

Results: Lu was produced with a specific activity of 100-110 GBq/mg. Lu-PDTMP was prepared with high radiochemical purity of greater than 99% and specific activity of 278 GBq/mmol. The complex demonstrated significant stability at room temperature. The agent demonstrated major accumulation in the bone tissue and a high target/nontarget uptake ratio. Dosimetric results showed that all tissues receive an insignificant absorbed dose in comparison with bone tissue.

Conclusion: The results showed that Lu-PDTMP has considerably better properties compared with clinically used bone-seeking radiopharmaceuticals and therefore can be a good candidate for bone pain palliative therapy in skeletal metastases; however, further biological studies in other mammals are still needed.