Phase 1 Study of the Effect of Icosapent Ethyl on Warfarin Pharmacokinetic and Anticoagulation Parameters

Abstract Background and Objective Icosapent ethyl (IPE) is a high-purity prescription form of eicosapentaenoic acid (EPA) ethyl ester approved to reduce triglyceride levels in patients with severe (C5.65 mmol/L) hypertriglyceridemia. EPA, the active metabolite of IPE, is mainly metabolized via b-oxidation, and studies suggest that omega-3 fatty acids such as EPA may have antithrombotic effects. The objective of this study was to evaluate the effect of IPE on the pharmacokinetic and anticoagulation pharmacodynamics of warfarin, a substrate of cytochrome P450 2C9-mediated metabolism. Methods Healthy adults received oral warfarin (25 mg) on day 1, oral IPE (4 g/day) on days 8-35, and coadministration on Day 29. Primary pharmacokinetic end points were area under the concentration-versus-time curve from zero to infinity (AUC 0-? ) and maximum plasma concentration (C max ) for R-and S-warfarin; pharmacodynamic end points were area under the international normalized ratio (INR) effect-time curve after the warfarin dose (AUC INR ) and maximum INR (INR max ). Results Twenty-five subjects completed the study. AUC 0-? and C max ratios of geometric means for both Rand S-warfarin following co-administration of warfarin with versus without IPE were within the 90 % confidence intervals of 0.80-1.25. AUC INR , INR max , and ratios were also similar. Conclusions IPE 4 g/day did not significantly change the single-dose AUC 0-? or C max of R-and S-warfarin or the anticoagulation pharmacodynamics of warfarin when coadministered as racemic warfarin at 25 mg. Co-administration of these drugs was safe and well tolerated in this study of healthy adult subjects. Key Points Patients who are candidates for icosapent ethyl therapy may also be receiving warfarin anticoagulation therapy. Icosapent ethyl 4 g/day did not have an effect on the pharmacokinetics or anticoagulation pharmacodynamics of warfarin. Co-administration of icosapent ethyl and warfarin was safe and well tolerated

Icosapent ethyl, a pure EPA omega-3 fatty acid: Effects on lipoprotein particle concentration and size in patients with very high triglyceride levels (the MARINE

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; $500 mg/dL) and previously demonstrated significant reductions in TG levels with no significant increases in low-density lipoprotein (LDL) cholesterol levels. OBJECTIVES: In this follow-up, exploratory analysis, we report the effects of IPE on lipoprotein particle concentration and size. METHODS: MARINE was a phase 3, multicenter, placebo-controlled, randomized, double-blind, 12-week study. Hypertriglyceridemic patients (N 5 229) were randomized to three treatment groups: IPE 4 g/day, IPE 2 g/day, or placebo. Lipoprotein particle concentrations and sizes were measured by nuclear magnetic resonance spectroscopy. RESULTS: Compared with placebo, IPE 4 g/day significantly reduced median concentrations of large very-low-density lipoprotein (VLDL; 227.9$500 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

Mechanistic studies of rabbit muscle glycogen phosphorylase

Glycogen phosphorylase catalyzes the reversible phosphorolysis of glycogen. The enzyme contains a molecule of pyridoxal phosphate (PLP), of which the phosphate moiety is essential for catalysis. To investigate the role of the cofactor phosphate moiety two phosphonate analogues of PLP, 5'-deoxypyridoxal-5'-methylenephosphonic acid (9) and5'-deoxypyridoxal-5'-difluoromethylene phosphonic acid (13), were prepared and reconstituted into apoglycogen phosphorylase b. Both such reconstituted enzymes had activities of approximately 25% - 30% of the native enzyme, and moreover, despite the considerable difference in cofactor pKa, the pH-dependences of Vmax, Km and Vmax/Kmfor the two enzyme systems were quite similar. These results suggest that PLP does not function as an essential acid catalyst in glycogen phosphorylase; rather they suggest that the cofactor phosphate remains dianionic throughout catalysis. Evidence concerning the protonation state of the PLP phosphate moiety within the R- and T-state enzyme conformations was obtained from solid-state magic angle spinning 31P NMR experiments of the native enzyme. The cofactor phosphate moiety, in both allosteric forms of the enzyme, exhibited axially symmetric shielding parameters. These results suggest that the PLP phosphate moiety exists as a dianion in both enzyme conformations, and therefore, that a change in protonation state does not accompany the allosteric transition. The compound, 1-nitro-D-glucal, was found to irreversibly inactivate both the R-and T-state forms of glycogen phosphorylase, behaving as an active site-directed affinity label. The pH-dependence of the inactivation was consistent with 1-nitro-D-glucalundergoing a conjugate addition reaction at the C-2 position with an active site nucleophile, possibly Tyr-573. X-ray structural studies of the inactivated T-state enzyme identified Tyr-573 as a likely candidate for the inactivation, and further, identified a surface amino acid (His-73) covalently bonded to the C-2 position of a second molecule of the affinity label, the product of a conjugate addition reaction. The cofactor-substrate analogues, pyridoxa1-5'-pyrophospho-1-a-D-glucose(PLPP-Glu) (21) and pyridoxa1-5'-pyrophospho-1-(2-deoxy-2-fluoro)-a-D-glucose(PLPP-2FG1u) (23), were prepared and reconstituted into apoglycogen phosphorylase b.Results from kinetic, 19F NMR and cofactor abstraction studies demonstrated that PLPP-2FG1u, unlike PLPP-Glu, is completely resistant to decomposition at the enzyme active site, and furthermore, does not transfer its glucosyl moiety to glycogen. Glycogen phosphorylase reconstituted with PLPP-2FG1u has allowed crystallization and initial structural analysis of the activated enzyme / substrate complex. The solution binding interaction between glycogen and phosphorylase has been probed by 19F NMR using a glycogen analogue in which all the non-reducing terminal glucosyl residues have been replaced by 4-deoxy-4-fluoro-glucosyl moieties (4-F-glycogen). Results from titrating the fluorinated glycogen analogue with phosphorylase suggest that 60 phosphorylase dimers bind per glycogen particle. 4-F-glycogen has also been investigated as an "incompetent" substrate analogue in an attempt to provide evidence for a glucosyl-enzyme intermediate in phosphorylase. Results from kinetic and radiolabelling studies demonstrated that the fluorinated glycogen analogue used was not completely inert to glucosyl transfer, but rather, that it possessed approximately 1% of the activity observed with normal glycogen, most likely due to incomplete derivatization of the glycogen.Science, Faculty ofChemistry, Department ofGraduat

A solid-state 31P-NMR investigation of the allosteric transition in glycogen phosphorylase b.

The catalytic role of the cofactor phosphate moiety at the active site of glycogen phosphorylase has been the subject of many investigations including solution-state high-resolution 31P-NMR studies. In this study the pyridoxal phosphate moiety in both the inactive and active forms of microcrystalline phosphorylase b has been investigated by high-resolution 31P magic-angle spinning NMR. The symmetry of the shielding tensor in model compounds at varying degrees of ionization is investigated and the results indicate a marked difference between the dianionic and monoanionic model compounds. Consequently the observed similarity in the principal tensor components describing the shielding tensor of the phosphorus nuclei present at the active site of both the R- and T-state conformations suggests that there is no change in ionization site upon activation in contrast to suggestions based upon isotropic shifts. Since previous relaxation measurements have pointed to the need to consider motional influences in such systems, several plausible models are considered. Subject to the assumption of congruency between the principal axis system describing the shielding interaction and molecular frame determined by the molecular symmetry axes, we conclude that the phosphate cofactor is dianionic in both forms

Icosapent ethyl, a pure EPA omega-3 fatty acid: Effects on lipoprotein particle concentration and size in patients with very high triglyceride levels (the MARINE study)

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; >= 500 mg/dL) and previously demonstrated significant reductions in TG levels with no significant increases in low-density lipoprotein (LDL) cholesterol levels. OBJECTIVES: In this follow-up, exploratory analysis, we report the effects of IPE on lipoprotein particle concentration and size. METHODS: MARINE was a phase 3, multicenter, placebo-controlled, randomized, double-blind, 12-week study. Hypertriglyceridemic patients (N = 229) were randomized to three treatment groups: IPE 4 g/day, IPE 2 g/day, or placebo. Lipoprotein particle concentrations and sizes were measured by nuclear magnetic resonance spectroscopy. RESULTS: Compared with placebo, IPE 4 g/day significantly reduced median concentrations of large very-low-density lipoprotein (VLDL; -27.9%; P = .0211), total LDL (-16.3%; P = .0006), small LDL (-25.6%; P = 500 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 omega-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. (C) 2012 National Lipid Association. All rights reserve