Olezarsen (Tryngolza): The apoC-III Antisense Drug Now Approved for Severe Hypertriglyceridemia - BALANCE, CORE and CORE2 (August 13, 2026)
Table of Contents
- A disease with almost no treatment - and the drug that changed it
- The target: apolipoprotein C-III (apoC-III)
- The mechanism: antisense oligonucleotide (ASO) with a liver-targeting sugar tag
- BALANCE: the FCS trial that earned the first approval
- CORE and CORE2: expanding to severe hypertriglyceridemia
- Olezarsen versus plozasiran: antisense meets siRNA
- Safety and what to watch
- What is still unknown
- The big picture
A disease with almost no treatment - and the drug that changed it
For most people, high triglycerides are a background lipid number nudged by diet, alcohol and metabolism. But at the extreme end sits familial chylomicronemia syndrome (FCS), a rare genetic disorder in which the body cannot clear fat from the blood. Triglycerides climb past 1,000 and sometimes 2,000 mg/dL, the blood can turn milky, and patients live under the constant threat of acute pancreatitis - a sudden, agonizing and potentially fatal inflammation of the pancreas. For decades the only real treatment was a punishing near-fat-free diet. Olezarsen, marketed as Tryngolza by Ionis Pharmaceuticals, changed that: on December 19, 2024 it became the first therapy ever approved by the FDA for FCS, and on June 24, 2026 it became the first and only treatment approved to reduce triglycerides and the risk of acute pancreatitis in the much larger severe hypertriglyceridemia (sHTG) population.
The target: apolipoprotein C-III (apoC-III)
Olezarsen works by turning down a single liver protein: apolipoprotein C-III, or apoC-III. ApoC-III sits on triglyceride-rich lipoproteins and acts as a brake on triglyceride clearance - it inhibits lipoprotein lipase, the enzyme that breaks down triglycerides, and slows the liver's uptake of triglyceride-rich remnant particles. People born with naturally low apoC-III tend to have low triglycerides and appear protected from heart disease, which made apoC-III one of the most attractive lipid targets in medicine. Lower the apoC-III, and the body clears triglycerides far more efficiently. That is exactly what olezarsen does.
The mechanism: antisense oligonucleotide (ASO) with a liver-targeting sugar tag
Olezarsen is an antisense oligonucleotide (ASO) - a short, chemically modified strand of genetic material designed to bind the messenger RNA that encodes apoC-III and mark it for destruction before it can be translated into protein. It is conjugated to GalNAc (N-acetylgalactosamine), a sugar tag that latches onto a receptor found almost exclusively on liver cells, concentrating the drug where apoC-III is made and allowing a small monthly dose. Because it acts on RNA rather than a circulating protein, olezarsen produces deep, durable apoC-III suppression. It is self-administered once a month with a prefilled subcutaneous autoinjector.
BALANCE: the FCS trial that earned the first approval
The first approval rested on the Phase 3 BALANCE trial, published in the New England Journal of Medicine in 2024. BALANCE randomized 66 adults with genetically confirmed FCS to olezarsen 80 mg, 50 mg, or placebo by subcutaneous injection every four weeks for 53 weeks. The 80 mg dose reduced fasting triglycerides by roughly 43 percentage points versus placebo at six months - a striking result in a disease where triglycerides had been essentially untreatable - and, critically, patients on olezarsen suffered far fewer episodes of acute pancreatitis than those on placebo. That combination of a dramatic triglyceride drop and fewer of the pancreatitis events patients actually fear is what secured the December 2024 FCS approval.
CORE and CORE2: expanding to severe hypertriglyceridemia
FCS affects only a few thousand people, but severe hypertriglyceridemia (sHTG) - triglycerides at or above roughly 500 mg/dL - affects millions and carries its own pancreatitis risk. To reach that population, Ionis ran two large Phase 3 trials with the TIMI Study Group: CORE (n=617) and CORE2 (n=446), together enrolling more than 1,000 adults. Placebo-adjusted fasting triglyceride reductions at six months were about 49 to 63 percent with the 50 mg dose and 55 to 72 percent with the 80 mg dose, sustained out to 12 months, alongside parallel drops in apoC-III, remnant cholesterol and non-HDL cholesterol. Most importantly, pooled acute pancreatitis events fell sharply, with a rate ratio of 0.15 (95% CI 0.05-0.40; P<0.001) at 12 months - an roughly 85% relative reduction. On these data the FDA broadened the label on June 24, 2026, ahead of the June 30 PDUFA date.
Olezarsen versus plozasiran: antisense meets siRNA
Olezarsen is not alone. Arrowhead's plozasiran (Redemplo), approved for FCS in November 2025, silences the very same apoC-III target - but through RNA interference (siRNA) rather than antisense, and it is dosed once every three months instead of monthly. That sets up one of the most interesting head-to-head stories in lipidology: two drugs, one target, two RNA technologies. Olezarsen reaches the market first in sHTG and offers a self-injected monthly autoinjector; plozasiran offers the convenience of quarterly dosing and is chasing the same sHTG indication with its SHASTA-3 and SHASTA-4 data. Real-world choice will likely turn on dosing preference, tolerability (olezarsen carries a thrombocytopenia and platelet-monitoring consideration), long-term durability and cost.
Safety and what to watch
Across trials the most common adverse effect was injection-site reactions, generally mild and transient. The signal that most distinguishes olezarsen within the antisense class is thrombocytopenia - reductions in platelet counts - so the label calls for platelet monitoring and cautions against use below a specified platelet threshold. Hypersensitivity reactions have also been reported. As with plozasiran, apoC-III-lowering therapies have shown modest effects on glucose control worth watching in people with diabetes. Olezarsen is a prescription injectable used under medical supervision - not a supplement or research chemical. Any 'olezarsen', 'Tryngolza' or 'ISIS 678354' offered by a research-chemical vendor is unverified and unsafe.
What is still unknown
The proven benefits of olezarsen so far are lower triglycerides and fewer acute pancreatitis events. What has not yet been established is whether it reduces hard cardiovascular outcomes - heart attacks and strokes - the way statins and, increasingly, the Lp(a) and PCSK9 agents aim to. Whether deep apoC-III lowering translates into fewer cardiovascular events in people with high triglycerides is the open question that will determine how broadly the apoC-III class is ultimately used, and it is being pursued in longer outcomes work.
The big picture
Olezarsen is a landmark on two fronts: it is a validation of antisense oligonucleotide medicine reaching a common metabolic disease, and it is the first drug to give patients with the most dangerous triglyceride disorders a real, approved option beyond diet. Together with the siRNA rival plozasiran, the Lp(a)-lowering agents pelacarsen, olpasiran, lepodisiran and zerlasiran, and the oral agents obicetrapib and muvalaplin, it is part of a rapid expansion of RNA- and small-molecule-based lipid therapies that are steadily converting genetic insights into approved medicines.
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Citations
- [1] Stroes ESG, et al. - Olezarsen for Familial Chylomicronemia Syndrome (BALANCE, Phase 3), New England Journal of Medicine (2024) Source
- [2] Ionis Pharmaceuticals - TRYNGOLZA (olezarsen) Approved in U.S. as First-Ever Treatment for Adults with Familial Chylomicronemia Syndrome (December 19, 2024) Source
- [3] Ionis Pharmaceuticals - TRYNGOLZA (olezarsen) Approved by the FDA for Severe Hypertriglyceridemia (June 24, 2026) Source
- [4] FDA - Approves First Treatment Shown to Reduce the Risk of Acute Pancreatitis in Adults with Severe Hypertriglyceridemia Source
- [5] HCPLive - FDA Approves Olezarsen (Tryngolza) for Severe Hypertriglyceridemia Source
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