New fluorine-18 pretargeting PET imaging by bioorthogonal chlorosydnone–cycloalkyne click reaction

Abstract

We report the first pretargeting in vivo study using the Strain-Promoted Sydnone–Alkyne Cycloaadition (SPSAC) reaction. The injection of a fluorine-18 labeled cyclooctyne three days after cetuximab bearing chlorosydnone moieties allowed a significant detection of the tumor by PET imaging suggesting an efficient click reaction inside the tumoral site. With a kinetic constant superior to 300 M⁻¹ s⁻¹, the SPSAC reaction might be an interesting tool, in addition to tetrazine-cyclooctene ligation, for in vivo chemistry.