99mTc(CO)3-VIP analogues: Preparation and evaluation as tumor imaging agent

Vasoactive intestinal peptide (VIP) receptors are expressed abundantly on many types of tumors and, hence, radiolabeled VIP analogues are being explored for tumor imaging and therapy. Here, we report synthesis of three VIP analogues and their radiolabeling with 99mTc via a novel tricarbonyl synthon. The radiolabeled product could be prepared in high yields (>95%) and stability. In vitro studies showed significant uptake of 99mTc(CO)3-VP05 in human colon carcinoma cells. Biodistribution studies in animal tumor model showed 0.4–1% ID/g tumor uptake.