Utility of biomarkers and imaging in the development of drugs for the treatment of coronary atherosclerosis
Can J Cardiol. 2012 May 22. [Epub ahead of print]
Biomarkers and imaging trials have often been used as guideposts in the development of drugs for atherosclerosis. This article explores the role of biomarkers and imaging trials in the development of 4 drugs: rimonabant, torcetrapib, ezetimibe, and niacin. Rimonabant, a selective cannabinoid-1 receptor, causes weight loss and exerts favourable effects on lipid biomarkers. An intracoronary ultrasound study showed no effect for the primary but significant benefit for the secondary end point. A large clinical outcomes trial was halted when it became apparent that the drug caused serious psychiatric side effects, including suicide.Torcetrapib, a cholesteryl ester transfer protein inhibitor, lowers low-density lipoprotein (LDL) cholesterol and induces a marked increase in high-density lipoprotein (HDL) cholesterol. However, a large clinical outcomes trial was halted very prematurely due to a 58% increase in all-cause mortality. Neutral imaging studies were reported later. Ezetimibe lowers low density lipoprotein cholesterol but did not reduce carotid intima-media thickness, and there is as yet no clinical trial evidence that it reduces cardiovascular events after a decade on the market. Niacin exerts favourable effects on lipid biomarkers and has shown regression of atherosclerosis in small carotid imaging trials, but did not reduce events in a recent clinical trial that was stopped early due to a lack of efficacy. In summary, favourable effects on lipid biomarkers often do not translate into clinical benefit, and imaging trials, which focus on a narrow measurement of atherosclerosis, are also often not helpful.