How long were FOURIER patients followed in total?

The parent trial had a median follow-up of 2.2 years. The open-label extension brought the total median follow-up from original randomization to approximately 5 years. Some patients were observed for over 7 years when accounting for variable enrollment timing.

Did evolocumab reduce cardiovascular death in the long-term data?

No statistically significant reduction in cardiovascular death was observed in either the parent trial or the OLE. A trend toward benefit appeared in the extension, but the crossover design (where placebo patients started evolocumab) reduced statistical power for this endpoint. The absence of a mortality signal remains FOURIER's most debated limitation.

Is it safe to keep LDL below 20 mg/dL for years?

FOURIER-OLE found no safety concerns with LDL levels below 20 mg/dL sustained over 5 years. Neurocognitive testing (EBBINGHAUS substudy), cancer rates, and hemorrhagic stroke rates were all comparable to higher-LDL groups. Current evidence supports the safety of very low LDL in patients with ASCVD.

Did evolocumab lose effectiveness over time?

No. LDL reductions were fully maintained through 5 years of follow-up. Anti-drug antibody development was negligible (<0.3%), and no neutralizing antibodies were detected. Evolocumab showed no evidence of tachyphylaxis.

How does FOURIER-OLE compare to ODYSSEY OUTCOMES long-term data?

ODYSSEY OUTCOMES, the major trial of alirocumab (a competing PCSK9 inhibitor), showed similar durability of benefit and safety in its extended analyses. Both trials support the drug class rather than one molecule. ODYSSEY OUTCOMES did show a nominally significant reduction in all-cause mortality in post-ACS patients, a result FOURIER did not replicate.

Why didn't all 27,564 patients enter the extension study?

Multiple factors contributed. Some patients had died. Others withdrew consent, were lost to follow-up, or declined additional participation. Regional regulatory approvals for the OLE varied. The 6,635 who enrolled were a self-selected group, which introduces survivorship bias into the extension results.

Did FOURIER-OLE change treatment guidelines?

Yes. The extension safety and efficacy data contributed to the 2022 ACC Expert Consensus Decision Pathway recommending PCSK9 inhibitors for ASCVD patients with LDL above 55 mg/dL after acute coronary syndrome. The data also reduced clinical hesitation about sustaining very low LDL levels long-term.

Does the FOURIER extension support using evolocumab for primary prevention?

Not directly. FOURIER enrolled only patients with established ASCVD (secondary prevention). Extrapolating to primary prevention requires separate trial evidence. Mendelian randomization data on PCSK9 loss-of-function variants suggest benefit in lower-risk populations, but no large RCT has tested this with evolocumab.

What was the cost-effectiveness impact of the extension data?

At its original list price (~$14,000/year), evolocumab was not cost-effective by most analyses. The combination of FOURIER-OLE showing growing benefit over time and Amgen reducing the net price by ~60% improved the cost-effectiveness ratio substantially, bringing it closer to commonly accepted thresholds of $100,000-$150,000 per quality-adjusted life year.

Were there any new safety signals in the extension that were not seen in the parent trial?

No. The OLE did not identify any new adverse event patterns. The numerical hemorrhagic stroke imbalance seen in the parent trial did not persist. No excess diabetes, cancer, neurocognitive decline, or hepatic injury was observed through 5 years.

FOURIER Extension Data and What Happened After the Trial Ended

Q: How does FOURIER-OLE compare to ODYSSEY OUTCOMES long-term data?

ODYSSEY OUTCOMES, the major trial of alirocumab (a competing PCSK9 inhibitor), showed similar durability of benefit and safety in its extended analyses. Both trials support the drug class rather than one molecule. ODYSSEY OUTCOMES did show a nominally significant reduction in all-cause mortality in post-ACS patients, a result FOURIER did not replicate.

Q: Why didn't all 27,564 patients enter the extension study?

Multiple factors contributed. Some patients had died. Others withdrew consent, were lost to follow-up, or declined additional participation. Regional regulatory approvals for the OLE varied. The 6,635 who enrolled were a self-selected group, which introduces survivorship bias into the extension results.

Q: Did FOURIER-OLE change treatment guidelines?

Yes. The extension safety and efficacy data contributed to the 2022 ACC Expert Consensus Decision Pathway recommending PCSK9 inhibitors for ASCVD patients with LDL above 55 mg/dL after acute coronary syndrome. The data also reduced clinical hesitation about sustaining very low LDL levels long-term.

Q: Does the FOURIER extension support using evolocumab for primary prevention?

Not directly. FOURIER enrolled only patients with established ASCVD (secondary prevention). Extrapolating to primary prevention requires separate trial evidence. Mendelian randomization data on PCSK9 loss-of-function variants suggest benefit in lower-risk populations, but no large RCT has tested this with evolocumab.

Q: What was the cost-effectiveness impact of the extension data?

At its original list price (~$14,000/year), evolocumab was not cost-effective by most analyses. The combination of FOURIER-OLE showing growing benefit over time and Amgen reducing the net price by ~60% improved the cost-effectiveness ratio substantially, bringing it closer to commonly accepted thresholds of $100,000-$150,000 per quality-adjusted life year.

Q: Were there any new safety signals in the extension that were not seen in the parent trial?

No. The OLE did not identify any new adverse event patterns. The numerical hemorrhagic stroke imbalance seen in the parent trial did not persist. No excess diabetes, cancer, neurocognitive decline, or hepatic injury was observed through 5 years.

By HealthRX.com Medical Team

Published May 25, 2026Updated May 25, 2026Last reviewed May 25, 2026

Clinical image for FOURIER Extension Data and What Happened After the Trial Ended Image: HealthRX.com clinical image

At a glance

| Detail | Value | |---|---| | Parent trial N | 27,564 | | OLE enrolled | 6,635 | | Intervention | Evolocumab 140 mg Q2W or 420 mg monthly + statin | | Comparator (parent) | Placebo + statin | | Median follow-up (parent) | 2.2 years | | Median follow-up (OLE, from randomization) | ~5 years | | Primary endpoint (parent) | CV death, MI, stroke, hospitalization for unstable angina, or coronary revascularization | | Key result (parent) | 15% relative risk reduction (HR 0.85, 95% CI 0.79-0.92) | | Key result (OLE) | ~20% relative MACE reduction with longer exposure |

Why the Parent Trial Left Questions Unanswered

FOURIER was a landmark trial. Published in March 2017, it randomized 27,564 patients with established atherosclerotic cardiovascular disease (ASCVD) who were already on optimized statin therapy to either evolocumab or placebo. Evolocumab dropped LDL cholesterol by 59%, from a median of 92 mg/dL to 30 mg/dL, and cut the composite MACE endpoint by 15%.

But the trial's median follow-up was only 2.2 years. That created real uncertainty on three fronts. First, the cardiovascular mortality curve had not separated. FOURIER showed reductions in MI and stroke but not in death from cardiovascular causes (HR 1.05, 95% CI 0.88-1.25). Critics argued that a drug costing over $14,000 per year at launch needed to prove it saved lives, not just prevented nonfatal events. Second, the LDL levels achieved were historically unprecedented in a large trial population. Median on-treatment LDL was 30 mg/dL, with a substantial fraction of patients below 20 mg/dL. Long-term safety at these levels was genuinely unknown. Third, the benefit curve appeared to be steepening at the end of follow-up, suggesting the trial may have stopped before the full treatment effect matured.

These gaps made extension data essential.

The Open-Label Extension: FOURIER-OLE Design

The FOURIER-OLE study enrolled 6,635 patients from the parent trial into an open-label phase where all participants received evolocumab. Patients originally assigned to evolocumab continued it. Patients originally assigned to placebo switched to active treatment. Follow-up from the original randomization date extended to a median of approximately 5 years.

This design has an inherent limitation worth naming: once the placebo group starts evolocumab, the between-group difference in cumulative LDL exposure narrows over time. Any comparison between original treatment arms during the OLE period is therefore conservative. If the drug works through cumulative LDL lowering (which the biology strongly suggests), the OLE will underestimate the true long-term benefit of uninterrupted treatment.

The OLE also introduced selection bias. Not all 27,564 parent-trial patients enrolled. Those who entered the extension were, on average, healthier and more adherent than those who did not. The investigators acknowledged this and conducted sensitivity analyses to address it.

Durability of LDL Lowering

One concern with monoclonal antibodies is immunogenicity, the possibility that patients develop anti-drug antibodies over time, blunting efficacy. FOURIER-OLE put that concern to rest. LDL reductions remained consistent through 5 years. Patients who had been on evolocumab since the parent trial showed no attenuation of effect. The median LDL stayed near 30 mg/dL throughout.

For the former placebo group, LDL dropped promptly once they started evolocumab in the OLE and reached the same levels as the original treatment arm within weeks. This is consistent with the pharmacology of PCSK9 inhibition: the mechanism targets circulating PCSK9 protein, and there is no tachyphylaxis pathway analogous to what can occur with receptor-based drugs.

Anti-drug antibody rates remained below 0.3%, with no neutralizing antibodies detected. This confirmed evolocumab's immunogenic profile is clinically irrelevant over extended use.

Extended Cardiovascular Outcomes

The most clinically meaningful finding from FOURIER-OLE was the growing separation in MACE curves. Patients originally randomized to evolocumab in the parent trial, who therefore had approximately 3 additional years of LDL lowering compared to the crossover group, showed an estimated 20% relative reduction in the primary composite endpoint across the full follow-up window.

The component-level results told a consistent story:

| Endpoint | Parent trial HR (2.2 yr) | Extended follow-up HR (~5 yr) | |---|---|---| | Composite MACE | 0.85 (0.79-0.92) | ~0.80 (estimated) | | MI | 0.73 (0.65-0.82) | Further reduction observed | | Ischemic stroke | 0.79 (0.66-0.95) | Maintained | | CV death | 1.05 (0.88-1.25) | Trend toward benefit, not significant |

The cardiovascular death signal moved in the right direction but did not reach statistical significance in the OLE. This was expected given the study's power limitations after crossover. Once both arms received evolocumab, the ability to detect a mortality difference collapsed. The investigators noted this explicitly.

What the extended data did confirm was that the FOURIER parent trial's steepening benefit curve was real, not an artifact. Longer LDL exposure translated into larger absolute risk reductions, consistent with the "lower for longer" hypothesis supported by Mendelian randomization studies of PCSK9 loss-of-function variants.

The "Lower for Longer" Principle in Context

Genetic data from large cohort studies had already shown that people born with PCSK9 loss-of-function mutations, who have lifelong LDL levels roughly 30-40 mg/dL below average, experience an 88% reduction in coronary events. That genetic signal is far larger than what any statin trial or PCSK9 inhibitor trial has shown, and the explanation is cumulative exposure. A 15% reduction over 2.2 years and a 20% reduction over 5 years fit the expected trajectory.

The 2018 AHA/ACC cholesterol guidelines cited FOURIER as primary evidence supporting PCSK9 inhibitors for very high-risk ASCVD patients whose LDL remains above 70 mg/dL on maximally tolerated statin therapy. The extension data strengthened that recommendation by showing that early initiation (rather than waiting for a second event) compounds benefit.

Safety Over Five Years

Neurocognitive Function

The single loudest safety concern when FOURIER launched was neurocognition. The brain is cholesterol-rich, and achieving LDL levels of 20-30 mg/dL raised theoretical questions about neurological harm. The EBBINGHAUS substudy, which prospectively assessed cognitive function in 1,204 FOURIER patients using the Cambridge Neuropsychological Test Automated Battery (CANTAB), found no difference between evolocumab and placebo across all cognitive domains through the parent trial.

The OLE extended that finding. No signal of cognitive decline emerged through 5 years of very low LDL levels. This is consistent with the biology: LDL in plasma does not cross the blood-brain barrier. The brain synthesizes its own cholesterol independently. The EBBINGHAUS extension data, combined with similar findings from the ODYSSEY OUTCOMES trial of alirocumab, effectively retired this concern for clinical practice.

Cancer

No increase in any cancer type was observed. Rates were balanced between arms in the parent trial and remained balanced through the OLE. This was consistent with prior statin safety data and with PCSK9 biology, which has no known oncogenic mechanism.

Hemorrhagic Stroke

The parent trial showed a numerical imbalance in hemorrhagic stroke (evolocumab 21 events vs. placebo 11). This was not statistically significant, but it prompted concern. Through the OLE, no persistent excess in hemorrhagic stroke was observed. The early imbalance appeared to be a chance finding, a conclusion also supported by the ODYSSEY OUTCOMES data.

Injection Site Reactions and Tolerability

Injection site reactions occurred in 2.1% of evolocumab patients versus 1.6% on placebo in the parent trial. Through the OLE, injection site events remained mild and did not lead to meaningful discontinuation. The 140 mg every-2-weeks and 420 mg monthly dosing schedules showed equivalent efficacy, giving patients flexibility.

New-Onset Diabetes

FOURIER-OLE reported no excess risk of new-onset diabetes, a finding that distinguishes PCSK9 inhibitors from high-intensity statins. The Repatha prescribing information does not list diabetes as a warning, and the extension data supported that label position.

Limitations the Investigators Acknowledged

The FOURIER-OLE team was transparent about several constraints. Selection bias was the most important: OLE enrollees were a self-selected, healthier subset. The crossover design meant that late comparisons were inherently underpowered for between-group differences. Loss to follow-up and variable time between parent trial completion and OLE enrollment added noise.

There was also the question of generalizability. FOURIER enrolled patients with established ASCVD on statins, the highest-risk secondary prevention population. Whether the extension data apply to primary prevention or to patients intolerant of statins requires separate evidence.

The trial was sponsored by Amgen, which manufactured evolocumab. The sponsor participated in study design, data collection, and analysis. Independent statistical verification was performed by the TIMI Study Group at Brigham and Women's Hospital, which provided a degree of academic oversight.

What Changed Clinically After FOURIER-OLE

The extension data influenced practice in three concrete ways. First, they reduced clinician hesitation about sustained very low LDL levels. Before FOURIER-OLE, many prescribers were uncomfortable maintaining patients at LDL <25 mg/dL indefinitely. Five-year safety data helped shift that calculus.

Second, the data supported earlier initiation. If the benefit of LDL lowering compounds over time, starting a PCSK9 inhibitor after a first ASCVD event rather than waiting for a recurrence makes sense from a cumulative-exposure standpoint.

Third, the extension data arrived alongside aggressive price reductions for evolocumab (Repatha's net price dropped by roughly 60% between 2018 and 2022). The combination of better long-term evidence and lower cost expanded real-world prescribing, particularly after the 2022 ACC Expert Consensus Decision Pathway recommended PCSK9 inhibitors for patients with LDL persistently above 55 mg/dL after an acute coronary syndrome.

Regression to the Mean: A Methodological Note

Some analysts raised the possibility that part of FOURIER's LDL reduction reflected regression to the mean, since patients were enrolled based on a single qualifying LDL measurement. The extension data argue against this being a major confounder. If the baseline LDL were artifactually elevated, the on-treatment values would have drifted upward over time as regression effects resolved. That did not happen. LDL remained stable at ~30 mg/dL across the full observation period, consistent with a genuine pharmacological effect rather than a statistical artifact.

Frequently asked questions

›

References

Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and Clinical Outcomes in Patients with Cardiovascular Disease. N Engl J Med. 2017;376(18):1713-1722. PubMed
O'Donoghue ML, Giugliano RP, Wiviott SD, et al. Long-Term Evolocumab in Patients With Established Atherosclerotic Cardiovascular Disease. Circulation. 2022;146(15):1109-1119. PubMed
Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC Guideline on the Management of Blood Cholesterol. Circulation. 2019;139(25):e1082-e1143. PubMed
Writing Committee, Lloyd-Jones DM, Morris PB, et al. 2022 ACC Expert Consensus Decision Pathway on the Role of Nonstatin Therapies for LDL-Cholesterol Lowering. J Am Coll Cardiol. 2022;80(14):1366-1418. PubMed
Repatha (evolocumab) Prescribing Information. Amgen Inc. Revised 2021. FDA Label
Cohen JC, Boerwinkle E, Mosley TH Jr, Hobbs HH. Sequence Variations in PCSK9, Low LDL, and Protection against Coronary Heart Disease. N Engl J Med. 2006;354(12):1264-1272. PubMed