PCSK9-IN-28 (Compound C11) is a PCSK9 inhibitor that can be isolated from Euphorbia esula. By binding to HNF1α, PCSK9-IN-28 inhibits PCSK9 transcription by binding to HNF1α and affecting its nuclear distribution, thereby enhancing LDLR and promoting LDL uptake. PCSK9-IN-28 exhibits significant lipid-lowering activity in the high-fat diet (HFD) mouse model and can be used in the study of hyperlipidemia.