99mTc-labeled colchicine for tumor imaging using DTPA as bifunctional chelating agent

For the purpose to develop novel Tc-99m-labeled tumor imaging agents with SPECT, colchicine (CHC) was directly labeled by Tc-99m using diethylene triamine pentacetate acid (DTPA) as bifunctional chelating agent. Trimethylcolchicinic acid, derivatived from colchicine, was conjugated to DTPA to get the new ligand DTPA-CHC, which was labeled by Tc-99m in the presence of SnCl2 as reducing agent. The radiochemical purity of the Tc-99m-DTPA-CHC complex was over 90 %. It had good hydrophilicity and was stable at room temperature. The high initial tumor uptake with moderate retention, good tumor/muscle ratios and satisfactory scintigraphic images highlighted the potential of Tc-99m-DTPA-CHC for tumor imaging.