Preparation and Preliminary Biological Evaluation of Al¹⁸FNOTA-GABA-KE108

Radionuclide labeled somatostatin analogs can specifically bind to somatostatin receptors (SSTRs) on the cell surface of neuroendocrine tumors (NETs) cells, so they can be used as a target for imaging or therapy of nets. In this study, a novel ¹⁸F-radiolabeled targeting SSTRs probe Al¹⁸FNOTA-GABA-KE108 was designed and synthesized, which linked 18F nuclide coupling bifunctional chelator (NOTA). Al¹⁸FNOTA-GABA-KE108 was obtained with high radiolabeling rate (60%-80%) and the total synthesis time was 30 min. After purification, the radiochemical purity was more than 95%. And the stability in vitro is excellent. In the SSTR-positive AR42J and BON1 tumor cells, the binding affinity between Al¹⁸FNOTA-GABA-KE108 and receptor (K_d=（1.34±0.60） μmol/L and （1.45±0.51） μmol/L, respectively) could be specifically inhibited, demonstrating high SSTR targeting ability. In normal KM mice and AR42J tumor bearing mice, Al¹⁸FNOTA-GABA-KE108 has high radioactivity accumulation in liver and kidney, which both indicate the same metabolic pattern. And a high uptake of radioactivity in adrenal gland and a high ratio of tumor to muscle uptake, similarly, demonstrate that Al¹⁸FNOTA-GABA-KE108 has excellent performance. These preliminary results provide some experimental basis for further study of Al¹⁸F labeled somatostatin analogues (KE108 complex) as tumor probes in the diagnosis of SSTR-positive tumors.