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Compare and contrast: two review articles on ezetimibe

For the past several years I have been following the ezetimibe controversy (see these posts on Gooznews and this blog here, here, here, here, here, here, here, here, here, here, here, here, here, here, and here).  In my view, we continue to lack evidence of ezetimibe’s clinical benefit, or even safety, 10 years after FDA approval.

I have a Google Scholar Alert for ezetimibe, so often links to articles on ezetimibe arrive in my email inbox.  Recently, two review articles on ezetimibe were published that were a study in contrasts.  The first, by Sheila Doggrell, takes a skeptical view toward ezetimibe and reaches the following conclusion:

The comparison of clinical trials with simvastatin and ezetimibe alone and together has clearly shown that simvastatin decreases LDL-cholesterol and this is associated with improved clinical outcomes. Also, ezetimibe alone or in the presence of simvastatin lowers LDL-cholesterol. However, ezetimibe alone or in the presence of simvastatin has not been shown to have any irrefutable beneficial effects on clinical outcomes. Thus, until/unless the use of ezetimibe is clearly shown to improve clinical outcomes, its use should be largely restricted to clinical trials investigating clinical outcomes, and ezetimibe should not be used routinely in everyday practice.

The second, by Binh An Phan, Thomas Dayspring and Peter Toth, takes a much more optimistic view:

In the current treatment of cardiovascular disease, many subjects fail to reach LDL-C targets or remain at high risk for CHD events despite optimal statin and medical therapy. Ezetimibe inhibits intestinal cholesterol absorption and is effective in lowering cholesterol as monotherapy or in combination with statins in several populations, including those with FH, sitosterolemia, and insulin resistance. Significant controversy has been generated regarding the clinical effectiveness of ezetimibe, particularly after the publication of ENHANCE and ARBITER-6 despite both trials having significant methodological flaws that limited their ability to evaluate the benefit of ezetimibe. Growing data suggest that ezetimibe in combination with statin has a positive effect on the progression of atherosclerosis and reduces cardiovascular events in subjects at risk for CHD, including those with chronic kidney disease. Results from IMPROVE-IT are forthcoming and may help to guide better the use of ezetimibe in very high-risk CHD populations. Until that time and based upon the current available data, ezetimibe should remain a viable adjunct to statin therapy in the treatment of hypercholesterolemia.

Dr. Phan and colleagues find reasons to dismiss the negative results of ENHANCE and ARBITER 6-HALTS as due to “methodological flaws” and use copious amounts of hand-waving to find support for ezetimibe in the SEAS and SHARP trials, even though those trials compared the combination of simvastatin and ezetimibe with placebo and thus can tell us nothing about what, if anything, ezetimibe added to those results.  Could the differing views of Doggrell and Phan et al. have anything to do with the fact that Dr. Doggrell declares no conflicts of interest relating to ezetimibe, while Phan, Dayspring and Toth declare the following conflicts:

Binh An Phan is a speaker for Abbott. Thomas Dayspring consults for Abbott, GSK, Health Diagnostic Labs, Kowa Company, Eli Lilly, Merck, Genentech, The Roche Group, Genzyme, and Omthera. He is on the Lecture Bureau for Abbott, GSK, Health Diagnostic Labs, Kowa, Eli Lilly, LipoScience, Merck. Peter P Toth is a speaker for Abbott, AstraZeneca, Amylin, Boehringer-Ingelheim, GSK, Kowa, Merck and consults for Abbott, Aegerion, AstraZeneca, Atherotech, Genzyme, Genentech, Kowa, and Merck.

It is not too surprising that authors who are consultants and on the speaker’s bureau for Merck would take a favorable view of ezetimibe.  What is surprising is that anyone would take their word for it.

References

Doggrell SA. The ezetimibe controversy — can this be resolved by comparing the clinical trials with simvastatin and ezetimibe alone and together? Expert Opin. Pharmacother. (2012) 13(10):1469-1480.

Phan BAP, et al. Ezetimibe therapy:  mechanism of action and clinical update. Vascular Health and Risk Management 2012:8:415-427.

Why the new indication for Vytorin and Zetia should not be approved

I have a guest post up at Merrill Goozner’s blog explaining why Merck’s application for a new indication for its drugs Vytorin (simvastatin/ezetimibe) and Zetia (ezetimibe) should not be approved.  The proposed indication is for the reduction of major cardiovascular events in patients with chronic kidney disease and is based on the results of the SHARP trial.  However, because SHARP compared the combination of simvastatin and ezetimibe with placebo — there was no simvastatin arm — we have no way of knowing if ezetimibe contributed anything to the result.  The FDA requires that combination drugs have additive effects over either drug alone.  Merck has not shown that ezetimibe contributed anything to the effect in SHARP, so the new indication should not be approved.

Addendum January 25, 2012:  Merck issued a press release today stating that the FDA did not approve the new indication.  “Because SHARP studied the combination of simvastatin and ezetimibe compared with placebo, it was not designed to assess the independent contributions of each drug to the observed effect; for this reason, the FDA did not approve a new indication for VYTORIN or for ZETIA® (ezetimibe) and the study’s efficacy results have not been incorporated into the label for ZETIA.”  The SHARP results were incorporated into the Vytorin label (see pages 27-28).

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