Production, biodistribution assessment and dosimetric evaluation of 177Lu-TTHMP as a bone pain palliation agent

Objective(s): Recently, bone-avid radiopharmaceuticals have been shown to have potential benefits for the treatment of widespread bone metastases. Although 177Lutriethylene tetramine hexa methylene phosphonic acid (abbreviated as 177Lu- TTHMP), as an agent for bone pain palliation, has been evaluated in previous studies, there are large discrepancies between the obtained results. In this study, production, quality control, biodistribution, and dose evaluation of 177Lu-TTHMP have been investigated and compared with the previously reported data. Methods: TTHMP was synthesized and characterized, using spectroscopic methods. Radiochemical purity of the 177Lu-TTHMP complex was determined using instant thin-layer chromatography (ITLC) and high performance liquid chromatography (HPLC) methods. The complex was injected to wild-type rats and biodistribution was studied for 7 days. Preliminary dose evaluation was investigated based on biodistribution data in rats. Results: 177Lu was prepared with 2.6-3 GBq/mg specific activity and radionuclide purity of 99.98%. 177Lu-TTHMP was successfully prepared with high radiochemical purity (>99%). The complex showed rapid bone uptake, while accumulation in other organs was insignificant. Dosimetric results showed that all tissues received almost insignificant absorbed doses in comparison with bone tissues. Conclusion: Based on the obtained results, this radiopharmaceutical can be a good candidate for bone pain palliation therapy in skeletal metastases.