Definition

A radiopharmaceutical tracer composed of the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 in which the serine residues (ser39) are replaced with cysteine (cys39) linked by the macrocyclic chelating agent 1,4,7-triazacyclononane-N,N’,N”-triacetic acid (NOTA), which is linked to maleimide (MAL), to the positron-emitting radionuclide gallium Ga 68, with potential use in diagnostic imaging upon positron emission tomography (PET)/computed tomography (CT). Upon administration of gallium Ga 68-NOTA-MAL-Cys39-exendin-4, the exendin-4 moiety binds to GLP-1R. The radionuclide moiety can be detected using PET/CT and GLP-1R-expressing tumors can be localized and visualized. GLP-1R, which is located on beta cells and regulates insulin secretion, is overexpressed on insulinomas, which are insulin-secreting neuroendocrine tumors (NETs).