Synthesis and Ready to Use Kit Formulation of EDTMP for the Preparation of 177Lu-EDTMP as a Bone Palliation Radiopharmaceutical

With its suitable nuclear decay characteristics and large-scale production feasibility with adequate specific activity, ¹⁷⁷Lu is regarded as an excellent radionuclide for developing bone pain palliation agent. Ethylenediamine-tetramethylene phosphonic acid (EDTMP) is a preferred carrier molecule for radiolanthanides, such as ¹⁷⁷Lu. The present paper describes the synthesis of EDTMP and the development of a ready-to-use kit for the preparation of ¹⁷⁷Lu-EDTMP and its quality control in accordance with the quality and safety criteria required for medicinal use.

EDTMP was synthesized by a modified Mannich-type reaction, and the structure was characterized using NMR and IR spectroscopy. Optimization of radiolabeling conditions was done with two different salt forms of EDTMP. The labeling yield was checked by paper chromatography with radiation detection. Kit was developed as a lyophilized mixture of EDTMP and sodium bicarbonate in a maximum volume of 5 mL. Labeling efficiency, radionuclidic purity, radiochemical purity, sterility, and pyrogenicity analysis were performed as the quality control of the labeled kit.

The analytical data for the structure determination and purity of the synthesized ligand were in agreement with authentic commercial samples used in radiopharmacy.¹⁷⁷Lu-EDTMP complex was prepared using synthesized EDTMP ligand under optimized labeling conditions with high labelling yield (>99%). The radiolabeling yields of the EDTMP kit at room temperature after 30 min and 48 hours were 99.46% and 99.00%.

The developed EDTMP kit enables an instant one-step preparation of the radiopharmaceutical of high radiochemical purity (>99%) and has a sufficiently long shelf life. This enables the routine production of the ¹⁷⁷Lu-EDTMP in nuclear medicine clinics without requiring experienced staff.