Gal-ARV-771, PROTAC prodrug, is a gal modified ARV-771. Gal-ARV-771 can be activated in SA-β-Gal-expressed cancer senescent cells to release ARV-771. Gal-ARV-771 induces selective degradation of BRD4 protein by the ubiquitin-proteasome pathway in senescent cells. Gal-ARV-771 promotes apoptosis of senescent cancer cells.