Biological Characterization of Ga-68 Somatostatin Peptidomimetic PET Imaging Agents

Overexpression of somatostatin receptors (SSTRs) is strongly associated with various endocrine and non-endocrine tumors, where expression of SSTR2 (subtype 2) is the most prevalent. Currently, FDA approved SSTR-targeting imaging agents, Octeoscan and NeoTect, are peptide-based and designed only for Single Photon Emission Computed Tomography (SPECT). However, due to less bio-stability of peptides, many cases of false results have limited their applications. Hence, to overcome these outstanding challenges, there is an utmost need to develop enhanced imaging agents with: (1) improved bio-stability using peptidomimetics; (2) access to a more sensitive imaging technique--Positron Emission Tomography (PET). This project intends to discover highly potent and selective somatostatin (SRIF) peptidomimetics labeled with 68Ga, which may serve as the leads for developing small molecule-based imaging agents targeting at SSTR2 with improved detection sensitivity, and also providing PET tracers for those hospitals without cyclotron for PET tracer production. The synthesis of two L-054,522-based peptidomimetic ligands is undergoing and will be labeled 68Ga in 2008. The specific aim of this subsequent project is to evaluate the feasibility of these novel 68Ga labeled peptidomimetics for in vivo SSTR2 imaging by means of SSTR2(+) tumor bearing mouse model and animal microPET imaging.

Project ID:PC9803-0012
External Project ID:NSC98-NU-E182-004