Torcetrapib and cholesterol. Computer illustration showing the structure of a molecule of the cholesterol-lowering drug torcetrapib (green), bound to a cholesteryl ester transfer protein (CETP) and high-density lipoprotein (HDL, yellow) complex. Lipoproteins are the major carriers of cholesterol in the blood and are mainly composed of lipids. CETP, also called plasma lipid transfer protein, is a plasma protein that facilitates the transport of cholesteryl esters and triglycerides between the lipoproteins. Torcetrapib was being developed to treat high cholesterol levels (hypercholesterolemia) and to prevent cardiovascular disease. However, its development was stopped in 2006 when phase III studies showed excessive mortality in the treatment group receiving a combination of atorvastatin (Lipitor) and torcetrapib.