Currently, the most commonly used chelator for labelling antibodies with ⁸⁹Zr for immunoPET is desferrioxamine B (DFO). However, preclinical studies have shown that the limited in vivo stability of the ⁸⁹Zr-DFO complex results in release of ⁸⁹Zr, which accumulates in mineral bone. Here we report a novel chelator DFOcyclo*, a preorganized extended DFO derivative that enables octacoordination of the ⁸⁹Zr radiometal. The aim was to compare the in vitro and in vivo stability of [⁸⁹Zr]Zr-DFOcyclo*, [⁸⁹Zr]Zr-DFO* and [⁸⁹Zr]Zr-DFO.

Azobenzene is the most extensively used class of chromophore in a large variety of applications.