A new 18F-heteroaryltrifluoroborate radio-prosthetic with greatly enhanced stability that is labelled by 18F–19F-isotope exchange in good yield at high specific activity

Abstract

An ¹⁸F-heteroaryltrifluoroborate was designed as a novel radioprosthetic for PET imaging. The stability of the new prosthetic was confirmed using ¹⁹F-NMR spectroscopy: the solvolytic half-life was measured to be >16 000 min. Conjugation to RGD gave a stable radiotracer precursor for kit-like labeling by ¹⁸F–¹⁹F isotope exchange in 15 min. The total radiosynthetic procedure including HPLC purification requires <45 min. A plasma stability assay showed negligible defluoridation following 150 min and stability is corroborated by in vivo imaging showing minimal bone uptake. With Curie levels of ¹⁸F–fluoride, yields of 20% and specific activities as high as 3 Ci μmol⁻¹ (110 GBq μmol⁻¹) are achieved (n = 3).