Imaging
Imaging study shows plaque regression with niacin vs placebo
October 30, 2009 Shelley Wood
Oxford, UK - A new imaging study is providing a first hint at the potential for niacin to help with plaque regression when used on top of optimized statin therapy. Writing in an early online edition of the
Journal of the American College of Cardiology (JACC)
, Dr Justin MS Lee (University of Oxford, UK) and colleagues report that 2 g of modified-release nicotinic acid (Niaspan, Abbott Laboratories) daily,
on top of statin, resulted in a 1.64 mm reduction in carotid wall area on MRI, compared with placebo, in patients with vascular disease and low HDL.
The paper comes as anticipation builds for the
ARBITER-HALTS6 study results. ARBITER-HALTS 6 is an imaging study comparing changes in carotid intima-media thickness in patients treated with
ezetimibe (Zetia, Merck/Schering-Plough) or extended-release
niacin; market analysts are already for niacin. As previously reported by
heartwire, ARBITER-HALTS 6 was stopped early: full results will be presented Monday, November 16, 2009 at the American Heart Association meeting in Orlando.
In the current study, niacin-treated patients experienced increases in HDL and decreases in LDL and triglycerides, accompanied by a 1.1 mm reduction in carotid wall area over the course of the 12-month study. By contrast, HDL levels in placebo-treated patients stayed more or less static, with more modest decreases in LDL and triglycerides, while carotid wall area actually increased by 1.32 mm
"There are a number of studies before this one—
HATS and
ARBITER 3—that have suggested findings consistent with ours, and I think what's new and important about this study is that it is the first one to show regression in patients who were taking established best contemporary treatment," senior author on the
JACC paper,
Dr Robin P Choudhury (University of Oxford, UK), told
heartwire. "This feeds into a bigger understanding of how this drug works, and it is very encouraging. To me, it absolutely focuses interest on those outcome studies, but we do need those studies."
Not only are large outcome trials key, but experts not involved in the study point out that an important question not answered by the imaging end points used in this study is whether nicotinic acid reduces the volume of lipid-rich core, something other MRI studies have specifically addressed. In an accompanying editorial,
Dr Farouc A Jaffer (Massachusetts General Hospital, Boston) writes, "it may be important to ascertain whether [nicotinic acid] therapy reduces carotid plaque lipid-rich/necrotic cores." Likewise,
Dr Roger Blumenthal (Johns Hopkins University, Baltimore, MD), commenting on the study for
heartwire, said he was not so sure that a regression of 1 mm in carotid wall area is "clinically meaningful."
"Usually with MRI, you talk about volume of plaque, and they are talking about area of plaque, which is a little bit confusing. . . . It's not like 30% of the lipid-rich core has gone away—that would be meaningful. These are minute changes and, in my mind, whether those will translate into better clinical outcomes in the two ongoing niacin studies remains to be determined."
The two much-anticipated outcome studies are
AIM-HIGH, due out in 2011, and
HPS2-THRIVE, anticipated to wind up in 2013.
To
heartwire, Choudhury agreed that the change in carotid wall area is "very modest."
"So, in terms of relieving a stenosis, for example, it is not clinically relevant. The point is the direction of change. Atherosclerosis has, for years, been considered a relentlessly progressive disease process.
To bring about a demonstrable reversal, however small, in only 12 months is mechanistically significant," he said. "Furthermore, remember that the plaque is heterogeneous. We don't know what compositional changes have been induced but if, for example, the lipid component had been reduced—and there are data from other studies to suggest this happens—then even a small change in total size could be very relevant to plaque behavior."
Asked why plaque volume was not the primary end point in the study, Choudhury said that carotid wall area is "effectively the same thing" as plaque volume.
"Volume is generated in other studies by multiplying the area of the wall by the MR slice thickness," he stated.
New results
The Merck KGaA-funded study by Lee et al was investigator-initiated and randomized 71 patients with low HDL (<40 mg/dL) to 2 g daily nicotinic acid (up-titrated over the first eight weeks), or placebo, on top of statin therapy, as dosed by the treating physician. To be enrolled in the study, patients needed to have carotid atherosclerosis, peripheral arterial disease, or type 2 diabetes and coronary artery disease. MRI was performed at baseline and at six and 12 months, with blood samples taken at the time of MRI.
In addition to the primary end point of absolute change in carotid artery wall area at one year—which was statistically significant, favoring the niacin-treated patients—investigators assessed change in aortic wall area and other measures of vascular function by MRI, none of which were statistically different between the niacin and placebo groups at one year.
Known side effects of niacin—flushing, itching, and gastrointestinal upset—were common in the study, and a full 20% of patients randomized to niacin withdrew because of drug side effects or MRI claustrophobia.
As Choudhury reminded
heartwire, niacin has "been around a long time," but, due largely to its side-effect profile, is now scarcely used in the UK and, to the best of his knowledge, is prescribed infrequently in the US. "It was the first drug that was demonstrated to be of benefit in secondary prevention after MI, but it fell by the wayside because the early preparations had problems with toxicity and tolerance. And in the meantime, statins came on the scene and of course were very effective in reducing mortality in a wide variety of patient groups."
Some caveats
On that background, however, Choudhury says the results of this latest study are intriguing, but with two caveats.
"One, we absolutely have to wait for the outcome studies before we make any comments on the appropriateness of niacin treatment in these patients. This is a very interesting study, but it's not definitive. Second, most patients experience some side effects with niacin, and the large majority experience some flushing. But with appropriate precautions, such as taking the drug at night, with aspirin, and perhaps having a light snack, [side effects] are manageable in most patients. So if it turns out in the outcome studies that there are, indeed, very significant benefits, then these side effects, in my view, are certainly liveable with."
Blumenthal, speaking with
heartwire, was more guarded, and said he felt the discussion in Lee et al's paper "went a bit overboard [portraying] niacin as a clear winner."
"I think they were very strong in their support of niacin, based on an absolute difference of 2/100ths of a square millimetre," he noted.
My English is not good. What does Niacin "on top of statins" mean?
Does that mean niacin "tops" statin for regression?
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