In brief
The long-awaited results answer a crucial question: can a large reduction in lipoprotein(a) prevent heart attacks, strokes, or cardiovascular deaths? In this trial, lowering the biomarker did not translate into fewer clinical events.
In brief: In the phase 3 Lp(a)HORIZON trial, monthly pelacarsen injections lowered lipoprotein(a), or Lp(a), by approximately 78% after one year. Yet the primary cardiovascular endpoint occurred in 12.3% of participants assigned to pelacarsen and 12.1% assigned to placebo during a median 4.7 years of follow-up. The hazard ratio was 1.02 (95% confidence interval 0.90–1.15). The study did not demonstrate that pelacarsen prevents cardiovascular events in the population tested. The findings were presented at the American Heart Association Scientific Sessions and published online in the New England Journal of Medicine on 7 November 2026. [1–3]
Evidence status · 7 November 2026
The complete trial report separates the laboratory response from the real-world event outcome
The primary endpoint was not reduced. These are outcomes from a trial of pelacarsen in secondary prevention, not evidence for all Lp(a)-lowering treatments.
What was Lp(a)HORIZON trying to prove?
Lp(a) is a largely inherited, LDL-like particle associated with atherosclerotic cardiovascular disease and calcific aortic valve disease. Epidemiological and genetic evidence supports its role as a causal risk factor. That evidence does not, by itself, establish that lowering Lp(a) with any particular medicine will prevent events. A randomized outcomes trial is needed to test that.
Pelacarsen is an investigational antisense oligonucleotide that reduces the liver's production of apolipoprotein(a), the distinctive protein component of Lp(a). Earlier studies had demonstrated large reductions in the blood marker. Lp(a)HORIZON was designed to test whether those reductions improved outcomes that matter to patients. [1–3]
The international, double-blind trial randomized 8,350 people with established cardiovascular disease and an Lp(a) concentration of at least 70 mg/dL. The reported primary efficacy analysis included 8,322 participants: 4,157 assigned to pelacarsen and 4,165 assigned to placebo. Participants received 80 mg of pelacarsen or placebo by subcutaneous injection every month, in addition to guideline-based cardiovascular prevention. Median follow-up was 4.7 years. [2,3]
This was a secondary-prevention trial. Its findings cannot automatically be applied to otherwise healthy people with elevated Lp(a) but no established cardiovascular disease.
The results: a substantial laboratory change, no demonstrated clinical benefit
| Prespecified measure | Pelacarsen | Placebo |
|---|---|---|
| Participants in the primary efficacy analysis | 4,157 | 4,165 |
| Primary cardiovascular endpoint | 511 (12.3%) | 503 (12.1%) |
| Median Lp(a) at month 12 | 64.4 nmol/L | 233.4 nmol/L |
Primary endpoint: time to the first cardiovascular death, nonfatal heart attack, nonfatal ischemic stroke, or urgent coronary revascularization requiring hospitalization. Hazard ratio: 1.02 (95% CI 0.90–1.15). The observed event proportion was 0.2 percentage points higher with pelacarsen; that numerical difference is not evidence the treatment increased cardiovascular risk. The trial's time-to-event analysis showed no statistically demonstrated reduction in the primary endpoint. [2,3]
At 12 months, the estimated placebo-adjusted difference in Lp(a) reduction was approximately 77.7%; the trial was also described as producing about a 78.4% reduction from baseline in the active-treatment group. These figures describe related but distinct comparisons and should not be confused with a reduction in heart-attack risk. [2–4]
The group with particularly high baseline Lp(a), at least 90 mg/dL, also showed no difference in the primary endpoint: 12.3% versus 12.3%, with a hazard ratio of 1.00 (95% CI 0.87–1.15). [3]
Were any cardiovascular outcomes improved?
The primary trial analysis did not find a significant reduction in the combined endpoint. Prespecified analyses of individual endpoint components and alternative cardiovascular composites were also broadly neutral. Extended analyses examined people while taking the study drug, those without major treatment interruptions, recurrent events, achieved Lp(a) concentrations, and baseline risk subgroups. Those analyses did not reveal convincing evidence of a subgroup with clinical benefit. [2–4]
This is more informative than the 4 September 2026 sponsor announcement, which reported only that the primary endpoint had not been met. The complete event counts, hazard ratios and more detailed safety information were reported 7 November 2026. The two dates should not be conflated. [1–4]
Safety: fewer serious adverse events overall, but important tolerability problems
The reported proportion experiencing a serious adverse event from any cause was 37.3% with pelacarsen and 41.1% with placebo. This does not mean that pelacarsen was safer overall. Several treatment-related symptoms and reactions were substantially more frequent with pelacarsen. [2,3]
Adverse events led to study-drug discontinuation in 20.6% of pelacarsen recipients compared with 7.5% receiving placebo. Investigators reported more flu-like symptoms and injection-site or hypersensitivity reactions. Anaphylaxis was reported in 19 people assigned to pelacarsen and none assigned to placebo; no deaths from those allergic reactions were reported. These safety findings matter independently of the neutral efficacy result. [2,3]
Does the trial prove that Lp(a) does not cause cardiovascular disease?
No. The result challenges a specific therapeutic assumption: that substantially lowering circulating Lp(a) with pelacarsen, for this duration, in people with existing cardiovascular disease and intensive background care, would reduce events. It does not overturn the broader genetic evidence linking lifelong high Lp(a) exposure with disease. [2–4]
Several explanations have been proposed, but none is established. A few years of lowering Lp(a) in adults with established disease may not reproduce decades of genetically lower exposure. Baseline prevention was also intensive: median LDL-C was approximately 65 mg/dL, and about 78% of participants were receiving high-intensity statins. Alternatively, differences in drug mechanism, exposure, tolerability, achieved reduction or the biology of the condition may matter. These are hypotheses for further research, not reasons to dismiss an unfavorable randomized result. [3]
The study cannot establish what would happen in primary prevention, with earlier treatment, with a different Lp(a)-lowering drug or after a different treatment duration.
What about olpasiran, lepodisiran and other investigational Lp(a) drugs?
The neutral result for pelacarsen does not establish the results of other drugs. Small interfering RNA agents, including olpasiran, lepodisiran and zerlasiran, and the oral investigational agent muvalaplin use different mechanisms or dosing approaches. Some have achieved even larger Lp(a) reductions in earlier-phase studies, but a larger biomarker change is not proof of fewer cardiovascular events. Each therapy needs its own outcome and safety evidence. [3,4]
For an overview of the evolving field, see our evidence-based Lp(a) guide.
What should people with high Lp(a) do now?
This result is not a reason to ignore Lp(a), and it is not a reason to stop established cardiovascular medicines. Lp(a) testing remains useful for assessing inherited risk, typically at least once in adulthood, with family testing where appropriate. The immediate practical response is to address risk factors with treatments and behaviors supported by outcome evidence: LDL-C and ApoB, blood pressure, smoking, diabetes management, physical activity and individualized cardiovascular-risk assessment. [2,3,5]
If you take a statin, ezetimibe, a PCSK9 inhibitor, or another prescribed therapy, do not stop or change it because of this trial. The benefits and indications of these treatments are separate from the pelacarsen result. Whether any investigational Lp(a)-specific treatment will improve outcomes remains an open question.
Frequently asked questions
Did pelacarsen reduce heart attacks and strokes?
Lp(a)HORIZON did not demonstrate a reduction in its primary composite of cardiovascular death, nonfatal heart attack, nonfatal ischemic stroke or urgent coronary revascularization. Individual outcomes and alternative composite analyses did not establish a cardiovascular benefit either. [2–4]
If my Lp(a) is high, should I still have it measured or discuss it with my clinician?
Yes. Lp(a) is still useful for understanding inherited cardiovascular risk. A neutral drug trial does not make the marker clinically irrelevant. [2,5]
Is pelacarsen an approved treatment for high Lp(a)?
As of the 8 November 2026 evidence review, pelacarsen is an investigational Lp(a)-lowering drug, not a routine approved treatment for reducing cardiovascular events. Its phase 3 outcome and tolerability results do not support describing it as a proven preventive therapy. [1–3]
What is the difference between lowering Lp(a) and lowering cardiovascular risk?
Lower Lp(a) is a biomarker effect. Lower cardiovascular risk means fewer heart attacks, strokes, urgent coronary procedures or cardiovascular deaths in appropriately designed trials. Lp(a)HORIZON demonstrated the first, not the second. [2–4]
Evidence sources and update history
- Cho L, et al. Pelacarsen and Cardiovascular Outcomes in Patients with High Lipoprotein(a). New England Journal of Medicine. First published online 7 November 2026. DOI: 10.1056/NEJMoa2610159.
- American Heart Association. Lp(a) HORIZON trial: Lp(a) fell by 78%, but cardiovascular outcomes unexpectedly neutral. Conference summary, 7 November 2026. Read the AHA report.
- Cleveland Clinic. Lipoprotein(a) Reduction With Pelacarsen Has No Impact on Cardiac Events, Lp(a)HORIZON Finds. Investigator report, 7 November 2026. Trial design, event counts and safety.
- Nissen SE, et al. Extended Analyses of Pelacarsen and Cardiovascular Outcomes in Patients with High Lipoprotein(a). NEJM Evidence. First published online 7 November 2026. DOI: 10.1056/EVIDoa2600373.
- ClinicalTrials.gov. Lp(a)HORIZON, NCT04023552.
- Novartis. Initial topline announcement, 4 September 2026. Historical milestone, superseded by the November results.
Editorial change log: Originally published 31 October 2026 as an analysis of the 4 September sponsor topline disclosure. Substantially updated 8 November 2026 after the full randomized trial and extended analyses were presented and published on 7 November. Retained original publication date; updated evidence date and clinical conclusions. The claim is editorially reviewed against linked sources, not independently medically certified.
Medical disclaimer: Educational research summary, not personal medical advice or an independently certified clinical review. Do not start, stop or change medications based on this page. Discuss treatment decisions with a qualified clinician.