18F-4FMFES

**18F-4FMFES** is a novel fluorine-18-labeled estradiol analogue developed as a PET radiotracer for non-invasive imaging of estrogen receptor (ER) expression, primarily in breast cancer. Structurally modified from parent 18F-fluoroestradiol (18F-FES) to introduce a fluorine at the 4-position and a methoxy group at the 11β-position, 18F-4FMFES exhibits improved metabolic stability, lower binding to plasma globulins, and reduced nonspecific tissue uptake, leading to significantly improved tumor-to-background contrast. Mechanistically, it acts as an estrogen receptor ligand, allowing highly sensitive and specific visualization of ER+ tumors, and can detect more breast cancer lesions than 18F-FES, improving diagnostic confidence in ER+ breast cancer imaging. It is not an approved commercial drug but is being evaluated in clinical studies, including phase II trials for ER+ breast cancer[1][6].

Other names

18F-4FMFES4-fluoro-11β-methoxy-16α-18F-fluoroestradiol