Abstract Click to copy section linkSection link copied! UDP-glucuronosyltransferase 1A8 (UGT1A8), a key human phase II metabolic enzyme, is related to the pathogenesis of endometrial and breast cancers. Nevertheless, its roles in drug–drug interactions and disease mechanisms remain unclear due to the lack of selective real-time monitoring tools. In this work, we developed UPro1A8, the first “off-on” fluorescent probe specifically targeting UGT1A8, designed via a “single-end modification strategy”.