Mutation in low-density lipoprotein receptor ( LDLR) or apolipoprotein B (ApoB) genes are major causes of familial hypercholesterolemia. PCSK9 was a third gene involved in familial hypercholesterolemia. Further work confirmed the interest of PCSK9 as an important target for cholesterol control in the general population. Clinical data obtained using antibodies to block its action (Phase 2 data from AMGEN) show up to 60% reduction in levels of LDL-c. With the PCSK9 target validated, companies are turning to the small molecule strategy but none have reported success and none has advanced to the clinical development stage. PCSK9 overexpression is pro-atherogenic, while its absence is protective.
A two-pronged strategy was adopted, such that it consisted of a directed synthesis approach based on human genetic data using cell based assays as well as an in silico screening using several docking pockets. Over 100 compounds from the directed synthesis program were screened in cell based assays and a number of hits compounds and chemical series, with enantiomeric selectivity, were identified which block PCSK9 secretion in HepG2 cells stably transfected with PCSK9 and also in wild type (non-transfected) HepG2 cells. The compounds that block PCSK9 secretion increase LDLR at the cell surface and increase cellular uptake of LDL-c in a dose-dependent manner.