[en] Objective: To investigate a new agent ¹⁵³Sm-ethylene diamine tetramethylene phosphonic acid (EDTMP)-nano-Hydroxyapatite (nano-HA) and the in vitro and in vivo performance of three derivatives of this agent aiming to explore a new radiopharmaceutical for targeting therapy of bone metastases. Methods: The nano-HA was synthesized by collosol-gelatum method, and was evaluated by transmission electron microscope (TEM) and X-ray diffraction (XRD). ¹⁵³Sm was produced with a high specific activity and excellent radionuclidic purity; adopting independent variable method, that nano-HA being labeled with ¹⁵³Sm by EDTMP transfer ligands in the best condition was investigated. The stability of ¹⁵³Sm-EDTMP-nano-HA in vitro was studied. ¹⁵³Sm-EDTMP-nano-HA was injected into normal rabbits for in vivo study. Both SMMC-7721 and MCF-7 cell lines were divided into three groups, treated with nano-HA, ¹⁵³Sm-EDTMP and ¹⁵³Sm-EDTMP-nano-HA, respectively, and the survival rate was measured by mono-nuclear cell direct cytotoxicity assay method. Results: The detection with TEM, XRD showed that nano-HA consisted of needle-like microcrystals. The labelling rate of ¹⁵³Sm-EDTMP-nano-HA was more than 95%, and was extremely stable in vitro. The scanning of normal rabbits showed that the skeletal system was clear , but other systems, for example, liver, spleen and kidney also were seen. The cell culture experiments in vitro indicated that ¹⁵³Sm-EDTMP-nano-HA strongly inhibited the proliferation of SMMC-7721 and MCF-7 cells. The half effective inhibition concentrations of ¹⁵³Sm-EDTMP-nano-HA were 1.98 and 0.075 mg/L, respectively; the half effective inhibition concentrations of nano-HA were 3.31 and 0.52 mg/L, respectively; the half effective inhibition concentrations of ¹⁵³Sm-EDTMP were 4.32 and 0.67 mg/L, respectively. Conclusion: ¹⁵³Sm-EDTMP-nano-HA shows it's fine biological properties, and it is well worth further researching as a promising radiopharmaceutical in nuclide treatment for bone metastases. (authors)