Solid-Phase Synthesis and Radiolabeling of a Bombesin Peptide Analog for Diagnostic Imaging of Tumors: A Preliminary Report

Abstract

Radiolabeled receptor-binding peptides have emerged as a clinically useful class of radiopharmaceuticals. The high binding affinity for its receptor facilitates retention of the peptide in receptor-expressing tissues while its relatively smaller size (compared to proteins and antibodies) results in rapid clearance from the blood and other non-target tissues [1]. Receptor-binding peptides labeled with γ-emitters can be used to visualize receptor-positive cells in vivo. Bombesin (BN) is a 14-amino acid peptide that binds to its receptor with high affinity. Specific receptors for BN have been identified on a variety of tumors including lung, breast, pancreas and prostate. BN receptors on various cancer cells may be important for the early diagnosis of cancers [2]. The aim of this study was to synthesize and evaluate a bombesin analog coupled to a chelating agent MAG3 (mercaptoacetyltriglycine) for labeling with ^99mTc for diagnostic imaging.