A Photocaged <i>N</i>‐Phosphonopiperidinone as a Selective Photo‐Cleavable DPP8/9 Inhibitor

The strategic introduction of photocages into chemical probes represents a powerful approach to generate spatiotemporally controlled tools with promising applications in chemical biology and drug discovery. This approach is particularly useful for inhibitors of proteins with cell-type-dependent functions, as they enable, via light-triggered selection, the study of their function in selected cells within multicellular organisms. The intracellular dipeptidyl peptidases 8 and 9 (DPP8/9) are serine hydrolases that act in a cell type-dependent fashion, in diverse biological processes such as inflammation and tumorigenesis. So far, no photocaged inhibitors for DPP8/9 are available, thus hampering their systematic investigations in biomedical research model systems such as mice. Herein, the development of a green light-cleavable, BODIPY-photocaged N-phosphono-piperidone-based DPP8/9 inhibitor is presented. This covalent-acting inhibitor is characterized by its photolysis properties, including a demonstration of its low phototoxicity, as well as potency and selectivity, in biochemical, biological, and, as an extension to these traditional validation approaches, chemical proteomics assays. These studies not only reveal the suitability of the developed photocages for cellular applications, as a prerequisite for their application in multicellular organisms, but also highlight the benefit of chemical proteomics workflows such as activity-based protein profiling for characterizing proteome-wide potencies and selectivities of photocaged compounds.