PURPOSE: Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the low 
density lipoprotein receptor (LDLR) and promotes degradation of the LDLR. 
Inhibition of PCSK9 either by reducing its expression or by blocking its 
activity results in the upregulation of the LDLR and subsequently lowers the 
plasma concentration of LDL-cholesterol. As a modality to inhibit PCSK9 action, 
we searched the chemical library for small molecules that block the binding of 
PCSK9 to the LDLR.
MATERIALS AND METHODS: We selected 100 chemicals that bind to PCSK9 where the 
EGF-AB fragment of the LDLR binds via in silico screening of the ChemBridge 
chemical library, using the computational GOLD algorithm analysis. Effects of 
chemicals were evaluated using the PCSK9-LDLR binding assay, immunoblot 
analysis, and the LDL-cholesterol uptake assay in vitro, as well as the fast 
performance liquid chromatography assay for plasma lipoproteins in vivo.
RESULTS: A set of chemicals were found that decreased the binding of PCSK9 to 
the EGF-AB fragment of the LDLR in a dose-dependent manner. They also increased 
the amount of the LDLR significantly and subsequently increased the uptake of 
fluorescence-labeled LDL in HepG2 cells. Additionally, one particular molecule 
lowered the plasma concentration of total cholesterol and LDL-cholesterol 
significantly in wild-type mice, while such an effect was not observed in Pcsk9 
knockout mice.
CONCLUSION: Our findings strongly suggest that in silico screening of small 
molecules that inhibit the protein-protein interaction between PCSK9 and the 
LDLR is a potential modality for developing hypercholesterolemia therapeutics.