Synthesis and biological evaluation of 99m Tc(CO) 3 (IDA‐CPT) for tumor imaging

This work reports the synthesis, radiolabeling, and preliminary biodistribution results in tumor‐bearing mice of 99m Tc(CO) 3 (IDA‐CPT). The novel camptothecin (CPT) derivate was successfully synthesized by conjugation of iminodiacetic acid (IDA) to camptothecin via a short carbonyl‐methylene linker. Radiolabeling was performed in high yield with [ 99m Tc(CO) 3 ] + core to get 99m Tc(CO) 3 (IDA‐CPT), which was hydrophilic and stable at room temperature. Biodistribution studies in tumor‐bearing mice showed that 99m Tc(CO) 3 (IDA‐CPT) accumulated in the tumor with good uptake and retention. However, its clearance from normal organs was slow, resulting in poor T/NT ratios. Further modification on the linker or/and 99m Tc‐chelate to improve the tumor‐targeting efficacy and in vivo kinetic profiles is currently in progress. Copyright © 2009 John Wiley & Sons, Ltd.