Study protocol and baseline characteristics of Randomized trial for Evaluation in Secondary Prevention Efficacy of Combination Therapy-Statin and Eicosapentaenoic Acid: RESPECT-EPA, the combination of a randomized control trial and an observational biomarker study

Background: Omega-3 polyunsaturated fatty acids (PUFAs) have been a hot topic since the Japan EPA Lipid Intervention Study (JELIS), the first landmark study using a highly purified eicosapentaenoic acid (EPA), indicated that EPA could decrease the incidence of cardiovascular events. Over 20 years have passed since the JELIS was conducted, and the standard treatment for dyslipidemia has altered significantly since then. The JELIS subjects did not undertake the current risk management especially current standard statins and did not exclusively target secondary prevention patients. In addition, the subjects included are relatively high EPA population. Furthermore, the clinical implication of the plasma EPA/arachidonic acid (AA) ratio as a biomarker has not yet been validated. Therefore, the Randomized trial for Evaluation in Secondary Prevention Efficacy of Combination Therapy - Statin and EPA (RESPECT-EPA) was planned and is currently underway in Japan.

Methods: The RESPECT-EPA comprises two parts: the open-label randomized controlled trial (RCT) and biomarker study (prospective cohort study design). The RCT included patients with a low EPA/AA ratio. These patients were then randomized to highly purified EPA (1800 mg/day) or control groups. The primary endpoint was cardiovascular death, non-fatal myocardial infarction, non-fatal ischemic stroke, unstable angina pectoris, and clinically indicated coronary revascularization. The biomarker study assesses the EPA/AA ratio's usefulness as a biomarker for cardiovascular events prediction.

Results: In the RCT, a total of 2,460 patients were enrolled in 95 sites in Japan. Patients' baseline characteristics were similar between intervention and control groups in the RCT. The baseline median EPA/AA ratio was 0.243 and 0.235, respectively. A total of 1,314 patients were participated in the observational part, and the baseline median EPA/AA ratio was 0.577.

Conclusions: After this study is completed, we will have further evidence on whether a highly purified EPA is effective in reducing cardiovascular events for secondary prevention or not, as well as whether if EPA/AA ratio is a predictor for future cardiovascular events. This study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN000012069).