Molecular rendering of the enzyme proprotein convertase subtilisin/kexin type 9 (PCSK9) (top) and an antibody (bottom). When PCSK9 binds to an LDLR, the receptor is destroyed along with the LDL particle. But if PCSK9 does not bind, the receptor can return to the surface of the cell and remove more cholesterol. New biopharmaceutical monoclonal antibody drugs act as a treatment to lower LDL cholesterol for adults who have a severe form of hereditary high cholesterol (familial hypercholesterolemia (FH) and people who require additional lowering of LDL cholesterol, when diet and statin treatment have not worked. PCSK9 inhibitors reduce the amount of cholesterol in the blood by improving the liver's ability to recycle low-density lipoprotein receptors. The PCSK9 inhibitor Alirocumab, known as brand name Praluent (Sanofi/Regeneron) is the first monoclonal antibody drug approved by the FDA