For years, people with a high lipoprotein(a) result have heard the same message: the number matters, and a drug to lower it is coming. On November 7, 2026, at the American Heart Association's Scientific Sessions in Chicago, the first large test of that promise came back neutral. In the Lp(a)HORIZON trial, the injectable drug pelacarsen lowered lipoprotein(a), or Lp(a), by about 78%, yet it did not reduce heart attacks, strokes or cardiovascular deaths compared with placebo. The main results were published the same day in The New England Journal of Medicine.
If you have had your Lp(a) measured, or are thinking about it, here is what the trial found, why experts were surprised, and why the test itself is still recommended.
What the Lp(a)HORIZON trial tested
Lipoprotein(a) is a cholesterol-carrying particle that looks like LDL cholesterol with an extra protein attached. Its level is set mostly by your genes, stays fairly stable through life, and barely responds to diet, exercise or statins. Large genetic studies show that people born with high Lp(a) have more heart attacks, strokes and narrowing of the aortic valve. Our guide to lipoprotein(a) as a heart risk marker explains the basics.
Pelacarsen is an antisense medicine: a short, synthetic strand of genetic material that tells the liver to make less of the Lp(a) protein. In the trial, about 8,300 adults in 42 countries received either a monthly pelacarsen injection or a placebo injection. Everyone already had cardiovascular disease, such as a prior heart attack, a stroke caused by a clot, or poor blood flow to the legs, and an Lp(a) level of at least 70 mg/dL (roughly 150 nmol/L). Most were already well treated: about three in four met their blood pressure and cholesterol goals, and most took a high-intensity statin.
What the trial found
The drug did its biochemical job. Lp(a) levels fell by roughly three quarters within a year. But the clinical results were essentially identical in both groups over a median follow-up of nearly five years.
| Measure | Pelacarsen | Placebo |
|---|---|---|
| Lp(a) change at 12 months | About 78% lower than placebo | Little change |
| Heart attack, stroke, urgent artery procedure or cardiovascular death | 12.3% | 12.1% |
| People with the highest Lp(a), 90 mg/dL or more | No benefit | No benefit |
| Stopped the injections because of side effects | About 21% | About 7.5% |
Pelacarsen also caused more flu-like reactions, injection-site reactions and allergic reactions, including rare severe ones. "I cannot avoid the disappointing conclusion: it didn't work," said Dr. Steven Nissen of Cleveland Clinic, the trial's senior author, in the AHA's news release.
Why lowering Lp(a) may not have prevented events
Nobody has a definitive answer yet. Researchers have put forward several explanations, which are not mutually exclusive:
- Too late in life: genetic studies reflect decades of lower Lp(a) from birth, while trial participants had lived with high levels for 60 years and already had advanced artery disease.
- Well-controlled background risk: with LDL cholesterol, blood pressure and inflammation already low, there may have been less room for another drug to help.
- Not low enough, or not for long enough: even after a 78% drop, some participants still had Lp(a) above the usual healthy range, and many stopped the injections.
- Something specific to this drug: newer agents work differently and lower Lp(a) further.
What the trial does not answer is just as important. It enrolled only people who had already had a cardiovascular event, so it says nothing about preventing a first heart attack. Four other large outcome trials are still running with different Lp(a)-lowering medicines: olpasiran (OCEAN(a)-Outcomes and OCEAN(a)-PreEvent), lepodisiran (ACCLAIM-Lp(a)) and the oral pill muvalaplin (MOVE-Lp(a)). Their results are expected over the coming years.
Should you still get your Lp(a) tested?
Yes, according to the trial's own investigators and current guidelines. The 2026 ACC/AHA multisociety cholesterol guideline recommends measuring Lp(a) at least once in adulthood, and that recommendation did not depend on having a drug. Nissen called the measurement "still absolutely worthwhile," because a high level usually causes no symptoms and tells you and your doctor that your heart risk is higher than your standard cholesterol numbers suggest.
That information still changes care today. A high Lp(a) can justify a lower LDL cholesterol goal, earlier or stronger statin therapy, closer attention to blood pressure and blood sugar, quitting smoking, and testing your parents, siblings and children, since the trait is inherited. Our article on lipoprotein(a) screening for every adult covers who benefits most, and our explainer on the 175 nmol/L threshold explains what very high values predict.
If you are taking part in one of the ongoing Lp(a) trials, the AHA release quotes Nissen advising participants not to withdraw because of this result.
Which tests can monitor or screen for this?
- Lipoprotein(a): a simple blood test, usually done once, reported in mg/dL or nmol/L. The two units cannot be converted with a single exact factor, so always check which one your lab uses.
- A standard lipid panel: total cholesterol, LDL, HDL and triglycerides. LDL remains the main treatment target, and our guide to normal LDL levels explains the ranges.
- Apolipoprotein B: counts all the particles that can clog arteries, including Lp(a). See our ApoB blood test guide.
- High-sensitivity CRP: a marker of low-grade inflammation, one of the factors examined in the trial's extended analyses. Read more about C-reactive protein.
- HbA1c and fasting glucose, plus kidney function, which also shape overall cardiovascular risk.
Recent scientific advances
Several peer-reviewed reviews published in the weeks before the full results set the stage. A review in The American Journal of Medicine listed the main reasons a drug might lower Lp(a) without preventing events, from treating too late to choosing patients whose other risk factors were already well controlled. A review in Current Atherosclerosis Reports described the newer generation of medicines, called small interfering RNAs, which can suppress Lp(a) production almost completely with injections given a few times a year, and an oral pill that blocks the particle from forming. Another review pointed out that the four remaining trials differ in who they enroll and what they count as an event, so their results will need careful comparison. In plain terms, scientists still see Lp(a) as a cause of heart disease; what is now uncertain is whether lowering it in adulthood reverses that risk, and for whom.
When to see a doctor
A high Lp(a) result is a long-term risk marker, not an emergency. Book a routine visit to discuss it, especially if a close relative had a heart attack or stroke at a young age, if you have very high LDL cholesterol, or if you have had a cardiovascular event despite good cholesterol control. Do not stop a statin or any other prescribed medicine because of news about pelacarsen. Call 911 right away for chest pain, sudden shortness of breath, or signs of stroke such as face drooping, arm weakness or trouble speaking.
Glossary
- Lipoprotein(a), Lp(a): an inherited cholesterol-carrying particle linked to heart attack, stroke and aortic valve narrowing.
- Antisense oligonucleotide: a short synthetic strand of genetic material that blocks the production of a specific protein.
- Small interfering RNA (siRNA): another type of gene-silencing medicine, usually given as infrequent injections.
- MACE: major adverse cardiovascular events, a combined count of heart attacks, strokes, urgent artery procedures and cardiovascular deaths.
- Placebo: an inactive treatment used for comparison in a clinical trial.
- Secondary prevention: care aimed at people who have already had a cardiovascular event, to prevent another one.
Frequently asked questions
Did pelacarsen lower Lp(a)?
Yes. Lp(a) fell by about 78% compared with placebo after one year, but the number of heart attacks, strokes and cardiovascular deaths did not change.
Does this mean Lp(a) is harmless?
No. Genetic and population studies still link high Lp(a) to cardiovascular disease. The trial shows that this particular drug, given to people with established disease, did not reduce events.
Is there any approved medicine to lower Lp(a)?
Not yet. Statins and lifestyle changes have little effect on Lp(a) itself. Other experimental drugs are still in large trials.
I have high Lp(a). What can I do now?
Work with your doctor to lower every other risk you can control: LDL cholesterol, blood pressure, blood sugar, weight and smoking. Ask whether your relatives should be tested.
Do I need to repeat my Lp(a) test?
Usually not, because the level is mostly genetic and stable. Your doctor may repeat it in specific situations, such as after a major illness or if the first result was borderline.
Sources
- Cho L, et al. Pelacarsen and Cardiovascular Outcomes in Patients with High Lipoprotein(a). N Engl J Med. 2026. DOI: 10.1056/NEJMoa2610159
- Nissen SE, et al. Extended Analyses of Pelacarsen and Cardiovascular Outcomes in Patients with High Lipoprotein(a). NEJM Evidence. 2026. DOI: 10.1056/EVIDoa2600373
- American Heart Association. Lp(a) HORIZON trial: Lp(a) fell by 78%, but cardiovascular outcomes unexpectedly neutral. November 7, 2026
- American College of Cardiology. Lp(a) HORIZON: Pelacarsen vs. Placebo in Patients With High Lp(a). 2026
- ClinicalTrials.gov. Lp(a)HORIZON, NCT04023552
- Sabouret P, et al. Pelacarsen and Lp(a)HORIZON: Interpreting the Disconnect Between Lipoprotein(a) Lowering and Cardiovascular Outcomes. Am J Med. 2026. DOI: 10.1016/j.amjmed.2026.10.005
- Parcha V, Bittner VA. RNA-Based Therapies for Lipoprotein(a) Reduction. Curr Atheroscler Rep. 2026. DOI: 10.1007/s11883-026-01474-4
- Moreira HG, et al. Five Trials, Five Different Questions: Design Heterogeneity Among Lipoprotein(a)-Lowering Cardiovascular Outcomes Trials After Lp(a)HORIZON. Cureus. 2026. DOI: 10.7759/cureus.117424
- Mach F, et al. 2025 Focused Update of the 2019 ESC/EAS Guidelines for the management of dyslipidaemias. Eur Heart J. 2025. DOI: 10.1093/eurheartj/ehaf190
- MedlinePlus. Lipoprotein (a) Blood Test. US National Library of Medicine
Further reading
- Lipoprotein(a): reading your heart risk level
- Lipoprotein(a) screening for every adult: what the 2026 guideline changes
- Very high Lp(a): the 175 nmol/L threshold
- Advanced lipid panel: ApoB, Lp(a) and deeper heart-risk testing
- Familial hypercholesterolemia screening in children
- Statins after 70: the STAREE trial
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