Did alirocumab reduce mortality in ODYSSEY OUTCOMES?

All-cause death was numerically lower with alirocumab (3.5% vs 4.1%, HR 0.85 to 95% CI 0.73-0.98). This result was nominally significant but did not meet the prespecified hierarchical testing threshold for formal statistical significance.

How much did alirocumab lower LDL cholesterol in the trial?

Mean LDL-C reduction was 62.7% at month 4. Median on-treatment LDL-C in the alirocumab group was approximately 40 mg/dL at month 4 and 48 mg/dL at month 48, reflecting the dose-titration protocol.

Which patients benefited most from alirocumab in ODYSSEY OUTCOMES?

Patients with baseline LDL-C ≥100 mg/dL showed the largest benefit (HR 0.76 to 95% CI 0.65-0.87). Those with baseline LDL-C below 80 mg/dL did not show a statistically significant benefit.

How does ODYSSEY OUTCOMES compare to the FOURIER trial?

Both trials demonstrated MACE reduction with PCSK9 inhibitors. ODYSSEY OUTCOMES enrolled higher-risk post-ACS patients and showed a suggestive mortality signal (HR 0.85), while FOURIER enrolled stable ASCVD patients and showed no mortality benefit. The NNT was approximately 63 in ODYSSEY OUTCOMES versus 74 in FOURIER.

When did the treatment benefit appear in ODYSSEY OUTCOMES?

Kaplan-Meier curves began to separate at roughly 12 months. Landmark analysis showed a stronger effect after 12 months (HR approximately 0.80) than in the first 12 months (HR approximately 0.90), consistent with gradual plaque stabilization.

What was the alirocumab dosing protocol in the trial?

All patients started on 75 mg subcutaneously every 2 weeks. The dose was increased to 150 mg at week 8 if LDL-C remained ≥50 mg/dL. Patients whose LDL-C fell below 15 mg/dL on two consecutive readings were switched to placebo in a blinded fashion.

Were there cognitive side effects with very low LDL-C in ODYSSEY OUTCOMES?

No. Neurocognitive adverse events occurred at similar rates in both groups (approximately 1.5%). The embedded EBBINGHAUS substudy confirmed no cognitive decline signal, even in patients achieving very low LDL-C levels.

What are the NNT and absolute risk reduction from ODYSSEY OUTCOMES?

The absolute risk reduction for the primary composite was 1.6 percentage points over 2.8 years, yielding a number needed to treat (NNT) of approximately 63.

Did ODYSSEY OUTCOMES change clinical guidelines for PCSK9 inhibitors?

Yes. The 2018 AHA/ACC cholesterol guideline update incorporated PCSK9 inhibitors as a recommended add-on for very high-risk ASCVD patients with LDL-C ≥70 mg/dL despite maximally tolerated statin therapy.

ODYSSEY OUTCOMES Results in Detail: Numbers, Subgroups, and Time Course

Q: What was the primary endpoint of ODYSSEY OUTCOMES?

The primary endpoint was a composite of coronary heart disease death, nonfatal myocardial infarction, ischemic stroke, or unstable angina requiring hospitalization. It occurred in 9.5% of alirocumab patients versus 11.1% of placebo patients (HR 0.85 to 95% CI 0.78-0.93).

By HealthRX Medical Team

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

At a glance

| Detail | Value | |---|---| | N | 18,924 | | Intervention | Alirocumab 75 or 150 mg SC every 2 weeks | | Comparator | Matching placebo | | Duration | Median 2.8 years (range up to ~5 years) | | Primary endpoint | Composite MACE: CHD death, nonfatal MI, ischemic stroke, unstable angina requiring hospitalization | | Key result | HR 0.85 (95% CI 0.78-0.93); p = 0.0003 |

Why This Trial Matters Beyond the Headline

ODYSSEY OUTCOMES was the second large cardiovascular outcomes trial for PCSK9 inhibitors, arriving roughly a year after FOURIER (evolocumab). Where FOURIER enrolled stable atherosclerotic disease patients, ODYSSEY OUTCOMES focused on a higher-risk population: patients 1 to 12 months after an acute coronary syndrome (ACS) event, already on maximally tolerated statin therapy. The trial's design differences, its dose-titration protocol, and its suggestive mortality signal make the granular results worth examining in full rather than stopping at the headline 15% MACE reduction.

Trial Design: Features That Shaped the Numbers

Patients were randomized 1:1 to alirocumab or placebo. A distinctive feature was the blinded dose-adjustment protocol. All patients started on alirocumab 75 mg every two weeks. At week 8, if LDL-C was ≥50 mg/dL, the dose was increased to 150 mg. If LDL-C fell below 15 mg/dL on two consecutive measurements, patients were switched to placebo in a blinded fashion to limit sustained very-low-LDL exposure. Roughly 7.7% of alirocumab-arm patients were switched to placebo for this reason.

This design choice was clinically prudent but analytically important. It means the treatment arm was not a fixed-dose comparison. The intention-to-treat analysis captures the full strategy (start 75, titrate up if needed, pull back if LDL drops too low), not just the pharmacology of a single dose.

Background statin use was high-intensity in approximately 89% of patients (atorvastatin 40-80 mg or rosuvastatin 20-40 mg), with the remainder on maximally tolerated lower doses plus ezetimibe in a subset. Median baseline LDL-C was 87 mg/dL, already well below the general population mean, reflecting the statin backbone.

Primary Endpoint: Composite MACE

The primary composite (coronary heart disease death, nonfatal myocardial infarction, ischemic stroke, or unstable angina requiring hospitalization) occurred in 903 of 9,462 patients (9.5%) in the alirocumab group versus 1,052 of 9,462 (11.1%) in the placebo group. The absolute risk difference was 1.6 percentage points over the median follow-up of 2.8 years.

| Outcome | Alirocumab (n=9,462) | Placebo (n=9,462) | HR (95% CI) | p-value | |---|---|---|---|---| | Primary composite MACE | 903 (9.5%) | 1,052 (11.1%) | 0.85 (0.78-0.93) | 0.0003 | | CHD death | 205 (2.2%) | 222 (2.3%) | 0.92 (0.76-1.11) | 0.38 | | Nonfatal MI | 626 (6.6%) | 722 (7.6%) | 0.86 (0.77-0.96) | 0.006 | | Ischemic stroke | 111 (1.2%) | 152 (1.6%) | 0.73 (0.57-0.93) | 0.01 | | UA requiring hospitalization | 37 (0.4%) | 60 (0.6%) | 0.61 (0.41-0.92) | 0.02 |

The NNT over 2.8 years was approximately 63 for the primary composite. For context, this compares to an NNT of roughly 74 in the FOURIER trial over 2.2 years for a slightly different composite (cardiovascular death, MI, stroke, hospitalization for UA, or coronary revascularization).

Secondary Endpoints and Individual Components

The prespecified hierarchical testing sequence controlled type I error across the primary and key secondary endpoints.

| Secondary endpoint | Alirocumab | Placebo | HR (95% CI) | |---|---|---|---| | Any CHD event | 12.7% | 14.3% | 0.88 (0.81-0.95) | | Any cardiovascular event | 14.0% | 15.6% | 0.89 (0.82-0.96) | | Composite of CHD death, nonfatal MI, ischemic stroke | 9.1% | 10.6% | 0.86 (0.79-0.93) | | All-cause death | 3.5% | 4.1% | 0.85 (0.73-0.98)* |

*The all-cause mortality result (HR 0.85 to 95% CI 0.73-0.98) was nominally significant but did not meet formal statistical significance in the hierarchical testing procedure because a prior secondary endpoint (composite of all-cause death, nonfatal MI, or ischemic stroke) had a p-value of 0.0013, which did cross its threshold, but the hierarchy required all preceding endpoints to be significant first. Cardiovascular death alone showed a non-significant HR of 0.88 (95% CI 0.74-1.05, p = 0.15).

This mortality signal, while not confirmatory, is clinically noteworthy. FOURIER showed no mortality benefit at all (HR 1.04 for cardiovascular death). Whether the difference reflects the higher-risk ACS population, longer follow-up accrual, or chance remains debated.

LDL-C Reductions: Median, Mean, and Distribution

At month 4 (before dose adjustments fully settled), alirocumab reduced LDL-C by a mean of 62.7% from baseline compared with a 0.8% reduction in the placebo arm. Median on-treatment LDL-C values in the alirocumab group were approximately 40 mg/dL at month 4 and 48 mg/dL at month 48, reflecting the dose-titration protocol and blinded placebo switches for very low levels.

The distribution matters. Patients starting with higher baseline LDL-C achieved larger absolute reductions. In the subgroup with baseline LDL-C ≥100 mg/dL (approximately one-quarter of enrollees), the primary endpoint HR was 0.76 (95% CI 0.65-0.87), a substantially larger effect than the overall cohort. Patients with baseline LDL-C <80 mg/dL showed a non-significant HR of 0.96.

This gradient strongly suggests that the degree of LDL lowering, not simply PCSK9 inhibition as a mechanism, drove the clinical benefit. The observation aligns with Mendelian randomization data and the broader statin literature linking each 1 mmol/L (39 mg/dL) LDL-C reduction to an approximate 22% MACE reduction per the CTT Collaboration meta-analysis.

Time-Course Pattern

The Kaplan-Meier curves for the primary endpoint began to separate at approximately 12 months and continued to diverge through 48 months. This lag is consistent with the biological model: atherosclerotic plaque stabilization and regression are not immediate effects of LDL lowering. The FOURIER trial showed a similar early-divergence timeline.

A prespecified landmark analysis examined events from randomization to 12 months and from 12 months onward separately. In the first 12 months, the HR was approximately 0.90 (not individually significant). From 12 months onward, the HR dropped to approximately 0.80, indicating an accumulating benefit with longer exposure. This time-dependent pattern has practical implications: patients and clinicians should not expect measurable event reduction in the first few months of PCSK9 inhibitor therapy.

Subgroup Analyses

The trial prespecified multiple subgroup analyses. Most showed consistent benefit, with two notable exceptions that shifted the magnitude of the effect.

| Subgroup | HR (95% CI) | |---|---| | Baseline LDL-C ≥100 mg/dL | 0.76 (0.65-0.87) | | Baseline LDL-C 80-<100 mg/dL | 0.84 (0.74-0.96) | | Baseline LDL-C <80 mg/dL | 0.96 (0.80-1.14) | | Age ≥65 | 0.84 (0.74-0.96) | | Age <65 | 0.86 (0.76-0.97) | | Diabetes at baseline | 0.84 (0.74-0.97) | | No diabetes at baseline | 0.86 (0.77-0.96) | | Prior CABG | 0.84 (0.68-1.03) | | eGFR <60 mL/min | 0.84 (0.68-1.05) |

The baseline LDL-C gradient was the clearest effect modifier. Patients already at low LDL on statin therapy alone (below 80 mg/dL) derived minimal additional benefit from adding alirocumab, a finding that shaped subsequent ACC/AHA guideline recommendations to prioritize PCSK9 inhibitors for patients with LDL-C ≥70 mg/dL despite maximally tolerated statin therapy.

Safety and Tolerability

Injection-site reactions were more common with alirocumab (3.8% vs 2.1%). Neurocognitive adverse events occurred at similar rates in both arms (approximately 1.5% each), an important finding given early concerns about very low LDL-C and cognition. The dedicated EBBINGHAUS substudy embedded within ODYSSEY OUTCOMES confirmed no cognitive decline signal with alirocumab.

Sustained LDL-C <15 mg/dL occurred in 4.4% of alirocumab patients. In these patients, the protocol mandated blinded dose reduction or switch to placebo. No excess adverse events were observed in this very-low-LDL subgroup, though long-term data beyond 5 years remain absent.

Anti-drug antibodies developed in 5.5% of alirocumab patients; neutralizing antibodies in 0.5%. These rates are consistent with biologic therapies generally and did not correlate with reduced efficacy in the trial's analysis.

Limitations Worth Noting

The trial enrolled post-ACS patients only. Extrapolation to primary prevention or stable chronic atherosclerotic disease requires caution, though the FOURIER trial covered the stable-disease population. The dose-titration design, while clinically appropriate, complicates pharmacokinetic interpretation and makes dose-response modeling less straightforward than fixed-dose trials. Median follow-up of 2.8 years limits conclusions about very long-term safety; the all-cause mortality signal, while encouraging, requires confirmation in longer or larger trials. The trial population was 74% white and 84% male, limiting demographic generalizability. Per the FDA label for alirocumab (Praluent), race-based and sex-based subgroup analyses showed consistent direction of effect, though confidence intervals were wide for smaller subgroups.

What Happened After Publication

Following publication in November 2018, the 2018 AHA/ACC cholesterol guideline update incorporated PCSK9 inhibitors as a treatment option for very high-risk ASCVD patients with LDL-C ≥70 mg/dL on maximally tolerated statin therapy. Sanofi/Regeneron subsequently reduced the list price of alirocumab by roughly 60% in 2019 to improve access and formulary positioning. Real-world adherence data have since shown that cost and prior authorization barriers remain the primary obstacles to PCSK9 inhibitor use in eligible patients. A post hoc analysis of ODYSSEY OUTCOMES published in 2020 confirmed that absolute benefit correlated with baseline cardiovascular risk, supporting a risk-stratified prescribing approach.

Frequently asked questions

›

References

Schwartz GG, Steg PG, Szarek M, et al. Alirocumab and cardiovascular outcomes after acute coronary syndrome. N Engl J Med. 2018;379(22):2097-2107. PubMed
Sabatine MS, Giugliano RP, Keech AC, et al. Evolocumab and clinical outcomes in patients with cardiovascular disease (FOURIER). N Engl J Med. 2017;376(18):1713-1722. PubMed
Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol. J Am Coll Cardiol. 2019;73(24):e285-e350. PubMed
Cholesterol Treatment Trialists' Collaboration. Efficacy and safety of LDL-lowering therapy among men and women: meta-analysis of individual data from 174,000 participants. Lancet. 2015;385(9976):1397-1405. PubMed
Praluent (alirocumab) prescribing information. Regeneron/Sanofi. FDA Label