BACKGROUND: Icosapent ethyl (IPE; formerly AMR101) is a high-purity prescription form of eicosapentaenoic acid ethyl ester. In the MARINE study we evaluated the efficacy and safety of IPE in patients with very high triglycerides (TG; 500mg/dL)andpreviouslydemonstratedsignificantreductionsinTGlevelswithnosignificantincreasesinlowβdensitylipoprotein(LDL)cholesterollevels.OBJECTIVES:Inthisfollowβup,exploratoryanalysis,wereporttheeffectsofIPEonlipoproteinparticleconcentrationandsize.METHODS:MARINEwasaphase3,multicenter,placeboβcontrolled,randomized,doubleβblind,12βweekstudy.Hypertriglyceridemicpatients(N5229)wererandomizedtothreetreatmentgroups:IPE4g/day,IPE2g/day,orplacebo.Lipoproteinparticleconcentrationsandsizesweremeasuredbynuclearmagneticresonancespectroscopy.RESULTS:Comparedwithplacebo,IPE4g/daysignificantlyreducedmedianconcentrationsoflargeveryβlowβdensitylipoprotein(VLDL;227.9500 mg/dL, IPE did not significantly change the overall sizes of LDL or HDL particles. CONCLUSION: IPE 4 g/day significantly reduced large VLDL, total LDL, small LDL, and total HDL particle concentrations and VLDL particle size in patients with TG $500 mg/dL. Changes in VLDL particle concentration and size reflect the TG-lowering effects of eicosapentaenoic acid. The reduction in LDL particle concentration with IPE is novel among u-3 therapies and is consistent with the previously reported reduction in apolipoprotein B and lack of LDL-C increase with IPE in patients with very high TG levels. Clinical trial registration number: NCT01047683