Senolysis Enabled by Senescent Cell‐Sensitive Bioorthogonal Tetrazine Ligation

Abstract Although the clearance of senescent cells has been proven to slow down the aging process and promote anti‐cancer chemotherapy, the development of senolytics remains challenging. Herein, we report a senolytic strategy enabled by senescent cell‐sensitive bioorthogonal tetrazine ligation. Our design is based on linking dihydrotetrazine (Tz) to a galactose (Gal) moiety that serves both as a recognition moiety for senescence‐associated β‐galactosidase and a caging group for the control of tetrazine activity. Gal‐Tz enables efficient click‐release of a fluorescent hemicyanine and doxorubicin from a trans ‐cyclooctene‐caged prodrug to detect and eliminate senescent HeLa and A549 cells over non‐senescent counterparts with a 16.44 senolytic index. Furthermore, we leverage the strategy for the selective activation and delivery of proteolysis‐targeting chimeras (PROTACs) as senolytics. PROTAC prodrug TCO‐ARV‐771 can be selectively activated by Gal‐Tz and delivered into senescent HeLa and A549 cells to induce the degradation of bromodomain‐containing protein 4. Senolytic PROTACs may offer an efficient way for intervention on cell senescence thanks to their unique capacity to degrade target proteins in a sub‐stoichiometric and catalytic fashion. The results of this study establish the bioorthogonal tetrazine ligation approach as a viable strategy for selective removal of senescent cells.