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

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 chlorosydnones moieties allowed a significant detection of the tumor by PET imaging suggesting 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 the tetrazine-cyclooctene ligation, for in vivo chemistry.