99mTc-exendin-4: Radiolabeling and quality control studies of glucagon-like peptide analog

Abstract

Aim: Exendin-4 is a type 2 diabetes antidiabetic drug that is a peptide agonist of the glucagon-like peptide 1 receptor (GLP-1R). Up to date, different exendin-4 compounds have been radiolabeled with many radioisotopes such as ⁶⁸Ga, ¹⁸F, ⁶⁴Cu and ^99mTc for various purposes like study of over expression of GLP-1R in insulinoma. The purpose of this study is to radiolabel exendin-4 with ^99mTc under appropriate conditions.

Methods: In this study, exendin-4 was labeled with ^99mTc, and quality control tests of ^99mTc-exendin-4 were done using ascending radioactive thin layer chromatography (RTLC). Also, the effects of important parameters such as the amount of reducing agent, pH value, incubation time, and radiation dose on the labeling efficiency were investigated. Then, the stability of ^99mTc-exendin-4 was assessed.

Results: According to the results, ^99mTc-exendin-4 was prepared with over 95 percent labeling efficiency by a novel, easy, and quick direct method with 30-min incubation time at pH 6.6. To achieve the best radiolabeling condition; 10 µg of exendin-4, 50 µg of stannous chloride (reducing agent) and 37 MBq ^99mTc was used. The RTLC studies indicated that ^99mTc-exendin-4 is stable up to 6 h in room temperature.

Conclusion: The obtained results demonstrated that radiolabeled exendin-4 may be a promising agent for GLP-1R imaging studies. Further studies are in progress in order to evaluate receptor binding capacity and biodistribution of the complex in experimental animals.