PCSK9-IN-28 (Compound C11) is a PCSK9 inhibitor that can be isolated from Euphorbia esula. It functions by binding to HNF1α, affecting its nuclear distribution, and thereby inhibiting PCSK9 transcription, which in turn enhances LDLR and promotes LDL uptake. In a high-fat diet (HFD) mouse model, PCSK9-IN-28 demonstrates significant lipid-lowering activity and can be utilized for hyperlipidemia research.