A new Japanese study of highly purified eicosapentaenoic acid (EPA; icosapent ethyl) has suggested a possible benefit in reducing adverse cardiovascular events in patients with chronic coronary artery disease taking statins.
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 (MI), nonfatal ischemic stroke, unstable angina, and coronary revascularization in patients allocated to the EPA product at a dosage of 1800 mg/day.
The results were presented at the American Heart Association (AHA) Scientific Sessions 2022 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 theheart.org | Medscape Cardiology, 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,” 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,” Nissen told theheart.org | Medscape Cardiology. “I don’t think it sheds any light at all on the debate over the efficacy of EPA in cardiovascular disease.”
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, 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, 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, 1800 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 2506 patients, 1249 assigned to the EPA group and 1257 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 1225 patients in the EPA group and 1235 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 µg/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 [HR], 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 µg/mL in the control group (182 patients) and those with an increase of less than 30 µg/mL in the EPA group (259 patients), the primary endpoint showed a significant reduction the EPA group (HR, 0.725; P = .0202).
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.
“Massive Loss” of Patients
Critiquing the study, Nissen highlighted the large dropout and protocol violation rate.
“There was a massive loss of patients over the 6- to 8-year follow-up, and the Kaplan- Meier curves didn’t start to diverge until after 4 years, by which time many patients had dropped out. It would have been a very selective population that lasted 6 years in the study. Patients that drop out are different to those that stay in, so they are cherry-picking the patients that persist in the trial. There is enormous bias here,” he commented.
“Another weakness is the open-label design. Everyone knew who is getting what. Blinding is important in a study. And there was no control treatment in this trial,” he noted.
The researchers also selected patients with low EPA levels at baseline, Nissen added. “That is completely different hypothesis to what was tested in the REDUCE-IT and STRENGTH trials. And even with all these problems, the results are still statistically insignificant.”
On the post hoc subgroup analysis showing a significant benefit, Nissen said, “They compared a subgroup in the active treatment arm who had large increases in EPA to a subgroup of control patients who had the smallest increase in EPA. That would be like comparing patients who had the largest reductions in LDL in a statin trial to those in the control arm who had no reductions or increases in LDL. That’s scientifically totally inappropriate.”
Supportive Data
But Bhatt argues that the RESPECT-EPA trial supports the two previous trials showing benefits of EPA.
“Some may quibble with the P value, but to me this study has shown clear results, with obvious separation of the Kaplan-Meier curves,” he said.
“It is an investigator-initiated study, which is good in principle but has some of the usual caveats of such a study in that — probably as a consequence of budget constraints — it has an open-label design and is underpowered. But as they did not use a placebo and still showed a benefit of EPA, that helps resolve the issue of the placebo used in REDUCE-IT for those who were concerned about it,” Bhatt noted.
He pointed out that the 1800-mg dose of EPA is the same dose used in the JELIS trial and is the dose used in Japan. The REDUCE-IT trial used a higher dose (4 g), but in general, Japanese people have higher levels of EPA than Western populations, he explained.
“While this trial included patients with lower levels of EPA, what is considered low in Japan is much higher than average American levels,” he added.
Magnitude of Benefit Uncertain?
Discussant of the study at the Late Breaking Clinical Trials session, Pam R. Taub, MD, professor of medicine at the University of California San Diego School of Medicine, said, “Despite being underpowered with a sample size of 2460, RESPECT-EPA shows benefit in decreasing composite coronary events.”
“There is benefit with EPA, but the magnitude of benefit is uncertain,” she stated.
Taub pointed out that there is a signal across studies for new-onset atrial fibrillation, but the absolute increase is “rather small.”
She noted that more mechanistic and clinical data are needed to hone in on which patients will derive the most benefit, such as those with elevated high-sensitivity C-reactive protein or highest change in EPA levels. But she concluded that in clinical practice, physicians could consider addition of EPA for reduction of residual risk in secondary prevention patients.
The RESPECT-EPA study was supported by the Japan Heart Foundation. Daida
reports s peakers’ bureau/honorarium fees from Novartis Pharma, Bayer Yakuhin, Sanofi, Kowa Company, Taisho Pharmaceutical, Abbott Medical Japan, Otsuka Pharmaceutical, Amgen, MSD, Daiichi Sankyo, Pfizer Japan, FUKUDA DENSHI, Tsumura & Co and TOA EIYO, and research funding from Philips Japan, FUJIFILM Holdings, Asahi Kasei, Inter Reha, TOHO HOLDINGS, GLORY, BMS, Abbott Japan, and Boehringer Ingelheim Japan.
American Heart Association (AHA) 2022 Scientific Sessions. Presentation 19455. Presented November 6, 2022.
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