In the placebo-controlled REDUCE-IT trial, icosapent ethyl (IPE) was linked to a significant reduction in major adverse cardiovascular events (MACE) when administered on top of LDL cholesterol control, but a new substudy suggests a greater relative advantage in those with a prior myocardial infarction.
In the study as a whole, IPE (Vascepa, Amarin) was tied to a 20% reduction in CV death (hazard ratio, 0.80; P = .03), but it climbed to a 30% reduction (HR, 0.70; P = .01) in the subgroup with a prior MI, reported a multinational team of investigators led by Prakriti Gaba, MD, a cardiologist at Brigham and Women’s Hospital, Boston.
On the basis of these data, “the imperative to treat patients who have a history of prior MI is even stronger,” said Deepak L. Bhatt, MD, executive director of interventional cardiovascular programs at Brigham and Women’s Hospital.
Dr. Deepak L. Bhatt
The principal investigator of REDUCE-IT and a coauthor of this subanalysis, Dr. Bhatt said in an interview, “The significant reduction in cardiovascular mortality, as well as sudden cardiac death and cardiac arrest, really should make physicians strongly consider this therapy in eligible patients.”
The main results of the REDUCE-IT trial were published more than 3 years ago. It enrolled patients with established CV disease or diabetes with additional risk factors who were on a statin and had elevated triglyceride (TG) levels.
A 25% reduction in MACE reported
In those randomized to IPE, there was about a 25% reduction in the primary composite MACE outcome of cardiovascular death, nonfatal MI, nonfatal stroke, revascularization, and unstable angina relative to placebo. About the same relative reduction was achieved in the key secondary endpoint of CV death, nonfatal MI, and nonfatal stroke.
Some guidelines have been changed on the basis of these data. The National Lipid Association, for example, conferred a class 1 recommendation for adding IPE to other appropriate lipid-reducing therapies in any individual 45 years of age or older with atherosclerotic cardiovascular disease.
This new substudy (J Am Coll Cardiol. 2022 Apr 25; doi: 10.1016/j.jacc.2022.02.035), is likely to be influential for those guidelines not yet revised. In the substudy of the prior MI patients, the relative benefit of IPE for the primary and secondary MACE endpoints were of similar magnitude to the overall study population, but events occurred more frequently in the prior-MI subgroup, greatly increasing the statistical power of the advantage.
More MACE in prior MI patients
For example, the primary outcome was observed in 22% of the placebo patients in the overall REDUCE-IT analysis but in 26.1% of those with prior MI, so even though the relative risk reduction remained at about 25%, the statistical strength was a hundred-fold greater (P = .00001 vs. P < .001).
For the key secondary composite MACE endpoint, the relative reduction for those with a prior MI was modestly greater than the study as a whole (HR 0.71 vs. HR. 075) but the statistical strength was again magnified in those with a prior MI (P = .00006 vs. P < .001). In those with a prior MI , the advantage of receiving IPE was similar whether or not there had been a prior revascularization.
The 20% lower rate of all-cause mortality among prior MI patients receiving IPE rather than placebo fell just short of statistical significance (HR, 0.80; P = .054). Ischemic events on IPE were reduced by 35% (P = .0000001) and recurrent MI was reduced by 34% (P = .00009).
In the substudy as well as in the REDUCE-IT trial overall, IPE was well tolerated. A slightly higher rate of atrial fibrillation was reported in both.
The REDUCE-IT substudy evaluated 3,693 patients with a history of MI, representing 45% of the 8,179 patients randomized.
IPE, an ethyl ester of the omega-3 polyunsaturated fatty acid, initially attracted attention for its ability to reduce elevated TG. It was hoped this would address reduce residual risk in patients on maximally reduced LDL cholesterol. However, it is suspected that IPE exerts benefits additive to or independent of TG lowering, according to the authors of the REDUCE-IT substudy. These include attenuation of the inflammatory response, release of nitric oxide, and effects that support stabilization of atherosclerotic plaque.
The investigators reported that the pattern of response supports this theory. In the newly reported substudy, the primary event curves that included nonthrombotic events separated at about 1 year, but even curves for CV death and sudden cardiac death were more delayed.
This delay might be explained “by the slow but steady reduction in plaque volume, mitigation of inflammation, improvements in endothelial function, and membrane stabilization,” according to the authors, who cited studies suggesting each of these effects might not be wholly dependent on TG reductions alone.