Commentary

Is ezetimibe/simvastatin no better than simvastatin alone? Lessons learned and clinical implications

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Full results are published, and the ACC is misquoted

The ENHANCE study was selected for a special presentation at the ACC annual scientific session on March 30, 2008. The full ENHANCE results were presented by Dr. Kastelein, after which an expert panel led by Harlan M. Krumholz, MD, discussed the trial’s implications. The ENHANCE results were simultaneously published in the New England Journal of Medicine ,1 accompanied by an editorial by B. Greg Brown, MD, and Allen J. Taylor, MD, 7 and another editorial by the editors of that journal, Jeffrey M. Drazen, MD, and colleagues. 8 The expert panel and the editorialists concluded that the ENHANCE trial data raised concerns about the cardiovascular benefits of ezetimibe; that statins should be used as initial therapy for hyperlipidemia and titrated to the goal LDL-C level or to the maximally tolerated dose; and that other drugs such as bile acid sequestrants, fibrates, and niacin should be used in combination with statins before considering ezetimibe. 9

The next day, stories appeared in the media mistakenly stating that the ACC had recommended that ezetimibe/simvastatin be discontinued. This view was fueled by an article in the ACC’s Scientific Session News , penned by a contract writer and editor, with the headline, “ACC on Vytorin: Go Back to Statins” that said, “After waiting for 18 months for the results of the ENHANCE study, an ACC panel on Sunday encouraged physicians to use statins as a first line and prescribe Vytorin only as a last resort for patients unable to tolerate other cholesterol-lowering agents.” 10

The ACC later clarified that this was the opinion of the panelists and not that of the ACC, and they reiterated statements from the AHA/ACC Secondary Prevention Guidelines 11 recommending statins in maximally tolerated doses or titrated to a goal LDL-C level for first-line drug treatment of coronary artery disease, and recommending that patients speak with their physicians before discontinuing any therapy.

WHY WERE THE ENHANCE STUDY RESULTS NEUTRAL?

The ACC expert panel concluded that the most likely reason for the neutral ENHANCE results was that ezetimibe lowers LDL-C but does not confer a cardiovascular benefit. In the words of Dr. Krumholz (as quoted by Shannon Pettypiece and Michelle Fay Cortez on bloomberg.com), ezetimibe is “just an expensive placebo.” 12

There are at least three potential explanations for the lack of benefit with ezetimibe in the ENHANCE trial. I list them below in order of lowest to highest probability, in my opinion:

Theory 1: Ezetimibe lowers LDL-C but is not antiatherogenic

Since almost all experts agree that lowering LDL-C confers cardiovascular benefits, if ezetimibe does not inhibit atherosclerosis it must have some “off-target” effect that negates its LDL-C-lowering benefit. Critics of ezetimibe point out that oral estrogen and torcetrapib also lower LDL-C but do not improve cardiovascular outcomes. 13,14

The lack of benefit with these two other agents can be explained. Oral estrogen does not lower apolipoprotein B (an indication of the number of atherogenic particles), but rather it increases the levels of both triglycerides and C-reactive protein, and it is prothrombotic in some people. 15 Torcetrapib increases aldosterone production and substantially raises blood pressure. 16 Therefore, both drugs have true off-target effects that could explain their failure to reduce cardiovascular risk despite reductions in LDL-C. (Interestingly, though, oral estrogen has been shown to slow the progression of carotid intima-media thickness in newly postmenopausal women. 17

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