UGT1A1-IN-1 (Compound 2) is a non-competitive inhibitor of UGT1A1. UGT1A1-IN-1 inhibits the 1-O-glucuronidation process mediated by UGT1A1 with an IC50 and a Ki value of 1.33 and 5.02 μM. UGT1A1-IN-1 can bind on UGT1A1 at the same ligand-binding site as Bilirubin . UGT1A1-IN-1 displays good reactivity in and human liver microsome (HLM). UGT1A1-IN-1 can serve as a fluorescent probe substrate for UGT1A1 or study bilirubin metabolism disorders.