Targeting APOC3 with Olezarsen in Moderate Hypertriglyceridemia — ESSENCE–TIMI 73b

Authors, Journal, Affiliations, Type, DOI

• Authors: Brian A. Bergmark, Nicholas A. Marston, Thomas A. Prohaska, Veronica J. Alexander, Andre Zimerman, Filipe A. Moura, Yu Mi Kang, Julia Weinland, Sabina A. Murphy, Erica L. Goodrich, Shuanglu Zhang, Dan Li, Maciej Banach, Erik Stroes, Michael T. Lu, Sotirios Tsimikas, Robert P. Giugliano, Marc S. Sabatine; for the ESSENCE–TIMI 73b Investigators
• Journal: New England Journal of Medicine 2025;393:1279–1291 (published online August 30, 2025)
• Affiliations: TIMI Study Group / Brigham and Women's Hospital / Harvard Medical School; Ionis Pharmaceuticals (Carlsbad, CA); Amsterdam University Medical Center; Medical University in Lodz; Yale School of Medicine; University of California San Diego
• Type: Phase 3, international, double-blind, randomized, placebo-controlled trial
• DOI: https://doi.org/10.1056/NEJMoa2507227
• Funding: Ionis Pharmaceuticals

Overview

ESSENCE–TIMI 73b enrolled 1,349 patients with moderate hypertriglyceridemia (TG 150–499 mg/dL) and elevated cardiovascular risk and randomized them 3:1 to monthly subcutaneous olezarsen (50 mg or 80 mg) versus placebo. At 6 months, both doses produced approximately 58–61 percentage-point placebo-adjusted reductions in triglyceride levels, and 85–89% of treated patients achieved normal TG (<150 mg/dL) compared to 12.5% with placebo. Olezarsen also substantially reduced apolipoprotein C-III (62–70%), remnant cholesterol (up to ~70%), VLDL-cholesterol (~57%), and non-HDL-C (~22%) without changing LDL-C. Safety was broadly acceptable with more injection-site reactions and mild transaminase elevations in the olezarsen groups, but no clinically significant hepatotoxicity or thrombocytopenia; no cardiovascular outcomes trial has been completed for this population.

Keywords

Hypertriglyceridemia; apolipoprotein C-III; olezarsen; antisense oligonucleotide; triglycerides; remnant cholesterol; cardiovascular risk; ESSENCE–TIMI 73b

Key Takeaways

Background and Rationale

• Hypertriglyceridemia is common and associated with increased atherosclerotic cardiovascular disease risk, yet highly effective therapies are lacking
• APOC3 (apolipoprotein C-III) is a central regulator of triglyceride metabolism, inhibiting lipoprotein lipase activity and hepatic uptake of TG-rich lipoprotein remnants
• Olezarsen is a GalNAc (N-acetylgalactosamine)-conjugated antisense oligonucleotide (ASO) that targets APOC3 messenger RNA, enabling hepatocyte-selective delivery
• Prior phase 2 data supported TG-lowering efficacy; olezarsen had been FDA-approved for familial chylomicronemia syndrome (FCS) but lacked phase 3 data in the broader moderate HTG population

Trial Design

• Phase 3, double-blind, randomized, placebo-controlled; 160 sites in North America and Europe (November 2022–February 2024)
• Eligibility: TG 150–499 mg/dL + elevated CV risk OR TG ≥500 mg/dL (severe HTG); minimum TG later amended to ≥200 mg/dL after regulatory feedback
• Randomized 1:3 to 50-mg or 80-mg cohort; within each cohort randomized 3:1 to olezarsen vs matching placebo (monthly SC)
• Treatment 12 months + 13-week safety follow-up
• Primary efficacy population: TG <500 mg/dL at baseline, ≥1 dose received (n=1,349: 254 olezarsen 50 mg, 766 olezarsen 80 mg, 329 placebo)
• Patients with severe HTG are the focus of separate CORE-TIMI 72a/72b trials

Baseline Characteristics

• Median age 64 years (IQR 56–70); 40.3% women; 92.8% White; 60.0% with diabetes mellitus
• 96.3% already on ≥1 lipid-lowering therapy
• Median baseline TG 238.5 mg/dL (IQR 190.5–307.5 mg/dL)

Primary Outcome — Triglyceride Reduction at 6 Months

• Olezarsen 50 mg: least-squares mean TG change −55.6% (95% CI −58.0 to −53.2) vs +2.8% placebo → placebo-adjusted −58.4 pp (95% CI −65.1 to −51.7; P<0.001)
• Olezarsen 80 mg: −57.8% vs +2.8% placebo → placebo-adjusted −60.6 pp (95% CI −67.1 to −54.0; P<0.001)
• Effects consistent across key clinical subgroups including diabetes status, statin use, and baseline TG level
• Possible interaction with fibrate use was observed but attributed to chance (fibrate subgroup was small)

Secondary Outcomes

• At 12 months: placebo-adjusted TG reduction −50.7 pp for both doses (P<0.001) — sustained but modest attenuation
• TG <150 mg/dL at 6 months: 85.0% (50 mg) and 88.7% (80 mg) vs 12.5% placebo (P<0.001)
• TG <150 mg/dL at 12 months: 82.8% and 85.0% vs 20.6% placebo (P<0.001)
• APOC3 reduction at 6 months: ~62% (50 mg) and ~70% (80 mg) vs placebo (P<0.001)
• Remnant cholesterol: ~−61.7% (50 mg) and ~−69.8% (80 mg) vs placebo (P<0.001)
• VLDL-cholesterol: ~−56.6% (50 mg) and ~−57.4% (80 mg) vs placebo (P<0.001)
• Non-HDL-C: ~−21.9% (50 mg) and ~−21.7% (80 mg) vs placebo (P<0.001)
• ApoB: ~−14.7% (50 mg) and ~−14.9% (80 mg) vs placebo (P<0.001)
• LDL-C: no significant change vs placebo (P=0.51 and P=0.72)
• HDL-C: modest increase with both doses vs placebo (P<0.001)

Cardiovascular Events (Exploratory)

• Major adverse cardiovascular events through 12 months: 7 (2.8%) in 50 mg group, 44 (5.7%) in 80 mg group, 14 (4.3%) placebo — trial was not powered for CV outcomes
• Acute pancreatitis: 0 (50 mg), 3 (0.4%, 80 mg), 0 (placebo) — rare; numbers insufficient for conclusions

Safety

• Serious adverse events: similar frequency across all groups
• Injection-site reactions: more common with olezarsen (mild severity predominantly)
• Aminotransferase elevations: mild elevations to any degree above ULN more common with olezarsen (50 mg: 34.2%; 80 mg: 38.3% vs 17.6% placebo; P<0.001 for both); however, no significant between-group difference for elevations >3× or >5× ULN; no case met Hy's law criteria
• Platelet count <100,000/µL: 2.2% (50 mg), 2.3% (80 mg) vs 0.8% placebo (P=NS for both); <75,000/µL in ≤1% in all groups; no thrombocytopenia stopping rules triggered
• Glycated hemoglobin: small increase noted in patients with pre-existing diabetes receiving olezarsen; no change in insulin resistance (HOMA-IR) or beta-cell function in either diabetic or non-diabetic patients
• Renal function (eGFR): monitored without significant clinically meaningful differences

Comparison with Other APOC3 Inhibitors

• Plozasiran (siRNA targeting APOC3): achieved ~57–79% APOC3 reduction and ~44–62% TG reduction in mixed hyperlipidemia — broadly comparable efficacy profile
• Class effect apparent: ASO (olezarsen) and siRNA (plozasiran) approaches show similar APOC3/TG reductions
• Parent compound volanesorsen (unmodified ASO) had more pronounced thrombocytopenia; GalNAc conjugation appears to mitigate this

Limitations of the Document

• Population scope: Primarily designed for moderate HTG — cannot be extrapolated to severe HTG (TG ≥500); dedicated trials (CORE-TIMI 72a/72b) ongoing
• Duration: 12 months only; long-term (>1 year) efficacy and safety not established
• Racial homogeneity: 92.8% White — results may not generalize to other racial and ethnic groups
• No CV outcomes: Trial was not powered for MACE; whether TG/remnant cholesterol/ApoB reductions translate into CV event reduction is unproven
• Industry sponsorship: Ionis Pharmaceuticals; data held by contract research organization (Medpace); first draft written by first author
• MACE imbalance: Higher MACE numerically in 80 mg group (5.7%) vs placebo (4.3%) — likely reflects imbalance in baseline risk or chance given lack of CV outcomes powering

Key Concepts Mentioned

• concepts/APOC3-Inhibition — central mechanism of action; olezarsen selectively silences hepatic APOC3 mRNA
• concepts/Dyslipidemia-Management — hypertriglyceridemia management; ASO/siRNA as emerging drug class for APOC3 inhibition
• concepts/Hypertriglyceridemia-Management — moderate HTG with elevated CV risk as primary target population; olezarsen as first phase 3-proven agent

Key Entities Mentioned

• entities/Olezarsen — the drug studied; GalNAc-ASO targeting APOC3; FDA-approved for FCS; now phase 3 data in moderate HTG

Wiki Pages Updated

• Created wiki/sources/olezarsen-essence-timi73b-nejm-2025.md
• Created wiki/concepts/APOC3-Inhibition.md
• Created wiki/concepts/Hypertriglyceridemia-Management.md
• Created wiki/entities/Olezarsen.md
• Updated wiki/concepts/Dyslipidemia-Management.md — expanded hypertriglyceridemia section with ESSENCE-TIMI 73b data
• Updated wiki/sourceindex.md
• Updated wiki/wikiindex.md