Clopidogrel versus Aspirin for Secondary Prevention in Coronary Artery Disease: A Comprehensive Meta-Analysis

Highlight

• In patients with established coronary artery disease (CAD), clopidogrel monotherapy significantly reduces major adverse cardiovascular or cerebrovascular events (MACCE) compared to aspirin.
• No significant difference in major bleeding or mortality was observed between clopidogrel and aspirin monotherapy during long-term follow-up.
• This evidence supports preferential use of clopidogrel over aspirin as secondary prevention in CAD patients, especially those post-percutaneous coronary intervention (PCI) or acute coronary syndrome (ACS).

Background

Coronary artery disease remains a leading cause of morbidity and mortality worldwide, necessitating effective secondary prevention strategies to reduce recurrent cardiovascular events. Aspirin monotherapy has been the cornerstone for long-term antiplatelet therapy in patients with established CAD, largely due to its proven efficacy, low cost, and familiarity in clinical practice. However, clopidogrel, a P2Y12 receptor inhibitor, offers an alternative mechanism of platelet inhibition and has shown benefits in combination with aspirin for certain indications.

Despite widespread use, comparative evidence on clopidogrel versus aspirin as monotherapy for secondary prevention—especially after the discontinuation of dual antiplatelet therapy—is limited and conflicting. Clarifying the relative efficacy and safety profiles of these agents can inform personalized treatment decisions and guideline recommendations.

Study Design

The current study is an individual patient data meta-analysis synthesizing results from seven randomized trials that compared clopidogrel monotherapy versus aspirin monotherapy in patients with established CAD. These patients mostly had a history of percutaneous coronary intervention or acute coronary syndrome and were eligible after cessation or absence of dual antiplatelet therapy.

The systematic search spanned multiple databases—PubMed, Scopus, Web of Science, and Embase—up to April 12, 2025. Eligible trials featured an initial period of dual antiplatelet therapy followed by randomization to either clopidogrel or aspirin monotherapy. The meta-analysis employed semi-parametric shared log-normal frailty models to address inter-trial heterogeneity and to estimate pooled hazard ratios (HRs) with comprehensive adjustment.

The primary efficacy endpoint was a composite measure of cardiovascular death, myocardial infarction, or stroke, collectively referred to as major adverse cardiovascular or cerebrovascular events (MACCE). The primary safety outcome was major bleeding, assessed per standardized criteria.

Key Findings

A total of 28,982 patients were included (14,507 clopidogrel; 14,475 aspirin), with median follow-up of 2.3 years (interquartile range 1.1 to 4.0 years). At an extended follow-up of 5.5 years, clopidogrel was associated with a statistically significant 14% reduction in MACCE compared to aspirin (HR 0.86, 95% CI 0.77–0.96, p=0.0082). Specifically, incidence rates were 2.61 events per 100 patient-years with clopidogrel versus 2.99 with aspirin.

Importantly, there was no statistically significant difference in mortality between groups. Major bleeding rates were numerically lower with clopidogrel but did not reach statistical significance (HR 0.94, 95% CI 0.74–1.21, p=0.64), indicating comparable safety profiles.

The analysis accounted for variability across trials, patient subgroups, and clinical settings, reinforcing the robustness and generalizability of the findings.

Expert Commentary

The findings provide compelling evidence favoring clopidogrel monotherapy over aspirin in secondary prevention of CAD, particularly in patients who have completed dual antiplatelet therapy after PCI or ACS. Clopidogrel’s more potent and selective inhibition of platelet aggregation mediated via P2Y12 receptor antagonism may explain its superiority in reducing ischemic events compared to aspirin’s irreversible cyclooxygenase inhibition.

While aspirin’s role as a foundational antiplatelet agent is well-established, this meta-analysis challenges the paradigm of indefinite aspirin monotherapy and suggests a shift toward clopidogrel in certain clinical scenarios. The comparable bleeding risk alleviates concerns related to safety trade-offs.

Nevertheless, considerations such as genetic polymorphisms affecting clopidogrel metabolism, cost, availability, and patient adherence should be factored into individual therapeutic decisions. Additionally, the meta-analysis acknowledges inherent limitations including heterogeneity in trial design, evolving background therapies, and potential publication bias.

Conclusion

This individual patient data meta-analysis demonstrates that clopidogrel monotherapy significantly reduces the risk of major cardiovascular events without increasing major bleeding compared to aspirin in patients with established CAD. These results advocate for reconsideration of clinical guidelines and support preferential use of clopidogrel over aspirin for long-term secondary prevention in this population.

Future research should focus on head-to-head randomized trials in diverse populations, cost-effectiveness analyses, and mechanistic studies to optimize antiplatelet strategies tailored to patient risk profiles.

Funding and Registration

The study was funded by Cardiocentro Ticino Institute and Ente Ospedaliero Cantonale, Switzerland. This meta-analysis is registered with PROSPERO, registration number CRD42025645594.

References

Valgimigli M, Choi KH, Giacoppo D, et al. Clopidogrel versus aspirin for secondary prevention of coronary artery disease: a systematic review and individual patient data meta-analysis. Lancet. 2025;406(10508):1091-1102. doi:10.1016/S0140-6736(25)01562-4.

Bhatt DL, Fox KA, Hacke W, et al. Clopidogrel and aspirin versus aspirin alone for the prevention of atherothrombotic events. N Engl J Med. 2006;354(16):1706-1717. doi:10.1056/NEJMoa060989.