111In-[Lys40(Ahx-DTPA)NH2]exendin (9–39) probe showed reasonable affinity to GLP-1R in vitro, whereas a biodistribution study demonstrated low specific uptake without efficient retention or internalization of the probe, with lower accumulation in rat insulinoma INS-1 tumors and lower INS-1 tumor/pancreas contrast ratio compared with GLP-1R agonist-based counterparts (77). The gene discussed is GLP1R; the disease is pancreatic insulinoma.