On the Viability of Tadalafil-Based F-Radiotracers for Phosphodiesterase 5 (PDE5) PET Imaging.

Phosphodiesterase 5 (PDE5) is a clinically relevant biomarker and therapeutic target for many human pathologies, yet a noninvasive agent for the assessment of PDE5 expression has yet to be realized. Such agents would improve our understanding of the nitric oxide (NO)/cyclic guanosine 3',5'-monophosphate (cGMP)/PDE5 pathway in human pathologies and potentially lead to novel uses of PDE5 inhibitors to manage lung conditions like SARS-CoV-2-mediated pulmonary inflammatory responses. In this study, efforts were made to produce an F-labeled analogue of the PDE5 inhibitor tadalafil to visualize PDE5 expression with positron emission tomography (PET).

Recent Advances in the Clinical Translation of Silicon Fluoride Acceptor (SiFA) F-Radiopharmaceuticals.

The incorporation of silicon fluoride acceptor (SiFA) moieties into a variety of molecules, such as peptides, proteins and biologically relevant small molecules, has improved the generation of F-radiopharmaceuticals for medical imaging. The efficient isotopic exchange radiofluorination process, in combination with the enhanced [F]SiFA in vivo stability, make it a suitable strategy for fluorine-18 incorporation. This review will highlight the clinical applicability of [F]SiFA-labeled compounds and discuss the significant radiotracers currently in clinical use.