Olezarsen
High EvidenceAn FDA-approved subcutaneous antisense oligonucleotide (ASO) from Ionis Pharmaceuticals, branded Tryngolza, that lowers triglycerides by silencing the messenger RNA for apolipoprotein C-III (apoC-III). Self-injected once a month, it was the first-ever therapy approved for familial chylomicronemia syndrome (FCS) on December 19, 2024, and on June 24, 2026 it became the first and only treatment approved to reduce both triglycerides and the risk of acute pancreatitis in the far larger severe hypertriglyceridemia (sHTG) population.
What It Is
Olezarsen (development codes ISIS 678354 / AKCEA-APOCIII-LRx, marketed as Tryngolza) is a GalNAc-conjugated antisense oligonucleotide (ASO) developed by Ionis Pharmaceuticals. It binds and triggers degradation of the messenger RNA that encodes apolipoprotein C-III (apoC-III), a liver-made protein that raises blood triglycerides by inhibiting lipoprotein lipase and slowing the clearance of triglyceride-rich lipoprotein remnants. By reducing apoC-III production, olezarsen restores lipoprotein lipase activity and speeds triglyceride clearance. It is given as a subcutaneous injection once a month, self-administered with a prefilled autoinjector. On December 19, 2024 the U.S. FDA approved olezarsen as Tryngolza, an adjunct to diet, for adults with familial chylomicronemia syndrome (FCS) - a rare, severe genetic disorder in which triglycerides can exceed 1,000 mg/dL and drive recurrent, life-threatening acute pancreatitis - making it the first therapy ever approved for FCS. On June 24, 2026, ahead of its June 30 PDUFA date, the FDA expanded the label to severe hypertriglyceridemia (sHTG), making olezarsen the first and only treatment approved to reduce triglycerides and the risk of acute pancreatitis in that much larger population. It is the antisense counterpart to Arrowhead's siRNA drug plozasiran (Redemplo), which targets the same apoC-III pathway but is dosed once every three months.
Regulatory Status
Olezarsen is FDA-approved under the brand name Tryngolza. It was first approved on December 19, 2024 as an adjunct to diet in adults with familial chylomicronemia syndrome (FCS) - the first therapy ever approved for that disorder. On June 24, 2026 the FDA broadened the approval to reduce triglycerides and the risk of acute pancreatitis in adults with severe hypertriglyceridemia (sHTG), the first and only treatment approved for that indication. It is developed by Ionis Pharmaceuticals and self-administered once monthly by subcutaneous autoinjector.
Why Researchers Study It
Olezarsen is the drug that broke a decades-long treatment vacuum for the most extreme triglyceride disorders. Familial chylomicronemia syndrome (FCS) is a rare genetic disease in which triglycerides run so high - often above 1,000 or even 2,000 mg/dL - that patients suffer repeated bouts of acute pancreatitis, a painful and potentially fatal inflammation of the pancreas, with essentially no effective treatment beyond a near-fat-free diet. Olezarsen became the first therapy ever approved for FCS, and then the first approved to cut acute pancreatitis risk in the much larger severe hypertriglyceridemia (sHTG) population - millions of people rather than the few thousand with FCS. It is a landmark proof point for antisense oligonucleotide (ASO) medicine and for apoC-III as a druggable target, and it sets up a defining head-to-head with the siRNA drug plozasiran: both silence apoC-III, but olezarsen is a monthly antisense injection while plozasiran is dosed once a quarter, framing a real-world choice between dosing convenience, durability, tolerability and cost.
Proposed Mechanisms
- Antisense oligonucleotide (ASO) that binds and degrades the messenger RNA encoding apolipoprotein C-III (apoC-III) in the liver, reducing apoC-III production
- GalNAc (N-acetylgalactosamine) conjugation targets delivery to liver hepatocytes via the asialoglycoprotein receptor, allowing a low monthly dose
- Lowering apoC-III restores lipoprotein lipase activity and speeds hepatic clearance of triglyceride-rich lipoprotein remnants, cutting blood triglycerides
- Also lowers apoC-III, remnant cholesterol, non-HDL cholesterol and apoB
- Reduces acute pancreatitis risk by removing the extreme chylomicronemia that triggers it
- Administered subcutaneously once a month, self-injected with a prefilled autoinjector
Evidence Snapshot
| Study Type | Model | Outcome | Link |
|---|---|---|---|
| Phase 3 (BALANCE, NEJM 2024) | 66 adults with genetically confirmed familial chylomicronemia syndrome (FCS); olezarsen 80 mg or 50 mg vs placebo subcutaneously every 4 weeks for 53 weeks | Olezarsen 80 mg reduced fasting triglycerides by about 43 percentage points versus placebo at 6 months (roughly -44% vs +54% placebo), with substantially fewer adjudicated acute pancreatitis events; the 50 mg dose showed a smaller, non-significant triglyceride change on the primary analysis | Source |
| Phase 3 (CORE and CORE2, TIMI Study Group) | 1,063 adults total with severe hypertriglyceridemia (CORE n=617; CORE2 n=446); olezarsen 50 mg or 80 mg vs placebo subcutaneously once monthly | Placebo-adjusted fasting triglyceride reductions at 6 months of about 49-63% (50 mg) and 55-72% (80 mg), sustained to 12 months, with parallel drops in apoC-III, remnant cholesterol and non-HDL cholesterol; pooled acute pancreatitis events fell with a rate ratio of 0.15 (95% CI 0.05-0.40; P<0.001) at 12 months - the basis for the June 2026 sHTG approval | Source |
| Phase 2 (multiple, prior) | Adults with high triglycerides, FCS and mixed hyperlipidemia across earlier dose-ranging studies | Dose-dependent apoC-III and triglyceride lowering that established the 50 mg and 80 mg monthly doses carried into the Phase 3 program | Source |
Commonly Discussed Benefits
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Safety & Cautions
- Thrombocytopenia (low platelet counts) has been reported with olezarsen and the antisense class; platelet monitoring is recommended, and it is contraindicated in people with a platelet count below the labeled threshold
- Long-term cardiovascular outcomes (heart attack and stroke reduction) have not been established; the proven benefits to date are triglyceride lowering and reduced acute pancreatitis events
- Injection-site reactions are the most common adverse effect; hypersensitivity reactions have also been reported
- As an injectable prescription medicine it must be used under the supervision of a healthcare provider; it is not a supplement or research chemical, and any 'olezarsen', 'Tryngolza' or 'ISIS 678354' sold by a vendor is unverified and unsafe
- It is dosed monthly rather than quarterly like the apoC-III siRNA plozasiran; the choice between them depends on dosing preference, tolerability, platelet considerations and access
Comparisons
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Citations
- [1] Stroes ESG, et al. - Olezarsen for Familial Chylomicronemia Syndrome (BALANCE, Phase 3), New England Journal of Medicine (2024) PubMed
- [2] Ionis Pharmaceuticals - TRYNGOLZA (olezarsen) Approved in U.S. as First-Ever Treatment for Adults with Familial Chylomicronemia Syndrome (December 19, 2024) PubMed
- [3] Ionis Pharmaceuticals - TRYNGOLZA (olezarsen) Approved by the FDA for Severe Hypertriglyceridemia (June 24, 2026) PubMed
- [4] FDA - Approves First Treatment Shown to Reduce the Risk of Acute Pancreatitis in Adults with Severe Hypertriglyceridemia PubMed
- [5] HCPLive - FDA Approves Olezarsen (Tryngolza) for Severe Hypertriglyceridemia PubMed
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