RESUMEN
Objective:To fulfill the automatic radiolabeling of the norepinephrine transporter (NET) trancer 18F-meta-fluorobenzylguanidine (mFBG), and explore the 18F-mFBG PET/CT imaging effect of pheochromocytoma. Methods:On the basis of the chemical structure of mFBG, a spirocyclic iodonium ylide was used as the precursor to undergo a 3-step reaction sequence (radiofluorination, deprotection and neutralization) on AllinOne synthesis module. Purification by high performance liquid chromatography and formulation were conducted to generate 18F-mFBG. The corresponding quality control tests of 18F-mFBG product was performed. Afterwards, a postoperative patient with pheochromocytoma underwent 18F-mFBG PET/CT imaging. Results:The radiosynthesis was accomplished within 70 min, and 18F-mFBG was obtained in (17.8±2.4)% non-decay-corrected radiochemical yield ( n=5), with radiochemical purity >97% and molar activity >59.2 GBq/μmol. Sterility test, bacterial endotoxins test, abnormal toxicity test and the acetonitrile residue all met the requirements of Pharmacopoeia of the People′ s Republic of China (2020 Volume Ⅳ). The 18F-mFBG PET/CT imaging disclosed high uptake in pheochromocytoma and clear localization of lesions. Conclusions:The automatic radiolabeling of the NET targeted tracer 18F-mFBG is successfully realized by commercially available synthesis module, and the production quality meets all requirements for clinical translation. 18F-mFBG has a potential to image neuroendocrine lesions in clinical setting.
RESUMEN
The 18 kDa translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor, is predominately localized to the outer mitochondrial membrane in steroidogenic cells. Brain TSPO expression is relatively low under physiological conditions, but is upregulated in response to glial cell activation. As the primary index of neuroinflammation, TSPO is implicated in the pathogenesis and progression of numerous neuropsychiatric disorders and neurodegenerative diseases, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), multiple sclerosis (MS), major depressive disorder (MDD) and obsessive compulsive disorder (OCD). In this context, numerous TSPO-targeted positron emission tomography (PET) tracers have been developed. Among them, several radioligands have advanced to clinical research studies. In this review, we will overview the recent development of TSPO PET tracers, focusing on the radioligand design, radioisotope labeling, pharmacokinetics, and PET imaging evaluation. Additionally, we will consider current limitations, as well as translational potential for future application of TSPO radiopharmaceuticals. This review aims to not only present the challenges in current TSPO PET imaging, but to also provide a new perspective on TSPO targeted PET tracer discovery efforts. Addressing these challenges will facilitate the translation of TSPO in clinical studies of neuroinflammation associated with central nervous system diseases.