99m Tc-labeled DTPA-colchicine dimer with improved tumor uptake.

This work reports the synthesis, radiolabeling, and biological studies of 99m Tc-diethylene triamine pentaacetic acid (DTPA)-colchicine dimer in tumor-bearing mice. The novel colchicine dimer was successfully synthesized by conjugation of DTPA to 2 colchicine biomolecules. The ligand could be labeled by 99m Tc in high yield to get 99m Tc-DTPA-colchicine dimer, which was hydrophilic and stable at room temperature. Biodistribution and imaging studies in tumor-bearing mice showed that 99m Tc-DTPA-colchicine dimer accumulated in the tumor with improved uptake and retention. The results indicate the need for synthetic modification of the parent colchicine derivative and the 99m Tc-chelate with a view to improve the tumor-targeting efficacy and in vivo kinetic profiles.

Synthesis, 99m Tc-labeling, and preliminary biological evaluation of DTPA-melphalan conjugates.

Melphalan (MFL) is a typical nitrogen mustard for the treatment of many types of cancer. For the purpose to develop novel 99m Tc-labeled tumor imaging agents with SPECT, MFL was directly labeled by 99m Tc using diethylene triamine pentacetate acid (DTPA) as bifunctional chelating agent. The novel ligands were successfully synthesized by conjugation of DTPA to MFL to get monosubstituted DTPA-MFL and bis-substituted DTPA-2MFL. Radiolabeling was performed in high yield to get 99m Tc-DTPA-MFL and 99m Tc-DTPA-2MFL, respectively, which were hydrophilic and stable at room temperature. The high initial tumor uptake with retention, good tumor/muscle ratios, and satisfactory scintigraphic images suggested the potential of 99m Tc-DTPA-MFL and 99m Tc-DTPA-2MFL for tumor imaging. However, the slow normal tissue clearance would be a great obstacle. Further modification on the linker and/or 99m Tc-chelate to improve the tumor targeting efficacy and in vivo kinetic profiles is currently in progress.