The open-label randomized RESPECT-EPA study showed a reduction of borderline statistical significance in its primary endpoint of a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal ischemic stroke, unstable angina, and coronary revascularization in patients allocated to the EPA product at a dosage of 1,800 mg/day.
The results were presented at the American Heart Association scientific sessions by Hiroyuki Daida, MD, Juntendo University Graduate School of Medicine, Japan.
However, the trial has several limitations, including a high number of patient withdrawals or protocol deviations, and as such, its conclusions are uncertain.
Regardless, it has inevitably added to the debate on the cardiovascular benefits of EPA, which were shown in the REDUCE-IT trial. However, that trial has been dogged with controversy because of concerns that the mineral oil placebo used may have had an adverse effect.
Commenting on the new RESPECT-EPA trial for this article, lead investigator of the REDUCE-IT trial, Deepak Bhatt, MD, said the results were consistent with REDUCE-IT and another previous Japanese trial, the Japan EPA Lipid Intervention Study (JELIS), and added to the evidence supporting cardiovascular benefits of EPA.
“In isolation, this study may not be viewed as showing conclusive benefits, but looking at the totality of the data from this trial and from the field more widely, this together shows a convincing cardiovascular benefit with EPA,” Dr. Bhatt said. “We now have 3 randomized controlled trials all showing benefits of highly purified EPA in reducing cardiovascular events.”
However, long-time critic of the REDUCE-IT trial, Steve Nissen, MD, Cleveland Clinic, was not at all impressed with the RESPECT-EPA trial and does not believe it should be used to support the EPA data from REDUCE-IT.
“The many limitations of the RESPECT-EPA trial make it uninterpretable. It just doesn’t meet contemporary standards for clinical trials,” Dr. Nissen said in an interview. “I don’t think it sheds any light at all on the debate over the efficacy of EPA in cardiovascular disease.”
Dr. Nissen was the lead investigator of another largescale trial, STRENGTH, which showed no benefit of a different high dose omega-3 fatty acid product including a combination of EPA and docosahexaenoic acid (DHA).
In his AHA presentation on the RESPECT-EPA study, Dr. Daida explained as background that in 2005, JELIS first demonstrated a beneficial effect of highly purified EPA on cardiovascular outcomes in patients with and without coronary artery disease.
Recently, optimal medical therapy, particularly with high-intensity statins, has become the gold standard of care for patients with coronary artery disease, but they are still at substantially high residual risk, he noted.
Despite of the evidence provided by JELIS, the conflicting results in recent omega-3 fatty acid trials (REDUCE-IT and STRENGTH) have led to an intense controversy regarding the relevance of EPA intervention on top of the latest optimal medical therapy, Dr. Daida said.
The current study – Randomized trial for Evaluating the Secondary Prevention Efficacy of Combination Therapy Statin and EPA (RESPECT-EPA) – was conducted to determine the effect of highly purified EPA on cardiovascular events in Japanese patients with chronic coronary artery disease and a low EPA/arachidonic acid (AA) ratio (< 0.4), who were already receiving statins.
They were randomly assigned to highly purified EPA (icosapent ethyl, 1,800 mg/day) plus statin therapy or to statin therapy alone.
The enrollment period started in 2013 and continued for 4 years. Patients were followed for a further 4 years from the end of the enrollment period.
The trial included 2,506 patients, 1,249 assigned to the EPA group and 1,257 to the control group. In both groups there were a high number of early withdrawals or protocol deviations (647 in the EPA group and 350 in the control group).
The analysis was conducted on 1,225 patients in the EPA group and 1,235 patients in the control group, although at 6 years’ follow-up there were fewer than 400 patients in each arm.
Baseline characteristics showed median low-density lipoprotein (LDL) cholesterol levels of 80 mg/dL, EPA levels of 45 mcg/mL, and triglyceride levels of 120 mg/dL.
The primary endpoint, a composite of cardiovascular death, nonfatal MI, nonfatal ischemic stroke, unstable angina, and coronary revascularization showed a borderline significant reduction in the EPA group at 6 years since the start of randomization (10.9% vs. 14.9%; hazard ratio, 0.785; P = .0547).
The secondary endpoint, a composite of sudden cardiac death, MI, unstable angina, and coronary revascularization, showed a significant reduction in the EPA group (8.0% vs. 11.3%; HR, 0.734; P = .0306).
In terms of adverse events, there was an increase in gastrointestinal disorders (3.4% vs. 1.2%) and new-onset atrial fibrillation (3.1% vs. 1.6%) in the EPA group.
In a post hoc analysis, which excluded patients with an increase of more than 30 mcg/mL in the control group (182 patients) and those with an increase of less than 30 mcg/mL in the EPA group (259 patients), the primary endpoint showed a significant reduction the EPA group (HR, 0.725; P = .0202).
Dr. Daida noted that limitations of the study included a lower than expected event rate (suggesting that the study may be underpowered), an open-label design, and the fact that baseline levels of EPA in this Japanese population would be higher than those in Western countries.