High Insulin Resistance Blunts the Superiority of Ticagrelor Over Clopidogrel in Minor Stroke Patients with CYP2C19 Mutations

Highlights

Ticagrelor-ASA significantly reduced the risk of recurrent stroke compared to clopidogrel-ASA in patients with low insulin resistance (HR 0.52, 95% CI 0.34 to 0.79).

The efficacy advantage of ticagrelor disappeared in patients with high insulin resistance (HR 0.96, 95% CI 0.74 to 1.24).

This interaction between insulin resistance and antiplatelet efficacy was independent of clinical diabetes status.

Safety outcomes, including severe or moderate bleeding, remained comparable across treatment groups regardless of insulin resistance status.

Background: The Challenge of Antiplatelet Resistance

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 inhibitor is the cornerstone of secondary prevention for patients with acute minor ischemic stroke or high-risk transient ischemic attack (TIA). For years, clopidogrel was the standard P2Y12 inhibitor. However, the efficacy of clopidogrel is hampered by genetic polymorphisms, specifically loss-of-function (LOF) mutations in the CYP2C19 gene, which impair the metabolic conversion of clopidogrel into its active form. The CHANCE-2 trial established that ticagrelor, which does not require metabolic activation, is superior to clopidogrel in these CYP2C19 LOF carriers.

Despite this advancement, a significant residual risk of recurrent vascular events remains. Emerging evidence suggests that metabolic factors, particularly insulin resistance (IR), play a critical role in platelet hyperreactivity. IR is not only a precursor to type 2 diabetes but also a systemic inflammatory state that enhances thrombotic potential through multiple pathways, including increased expression of P-selectin and activation of the arachidonic acid pathway. Understanding how IR modulates the response to potent P2Y12 inhibitors like ticagrelor is essential for personalizing secondary prevention strategies.

Study Design: A Deep Dive into the CHANCE-2 Post Hoc Analysis

This study was a post hoc analysis of the Clopidogrel in High-Risk Patients with Acute Nondisabling Cerebrovascular Events II (CHANCE-2) trial. The original trial was a multicenter, double-blind, randomized controlled trial conducted in China, involving patients with minor stroke or TIA who were identified as CYP2C19 LOF carriers.

The analysis included 4,954 patients who were randomized to receive either ticagrelor (180 mg loading dose, followed by 90 mg twice daily) plus aspirin or clopidogrel (300 mg loading dose, followed by 75 mg daily) plus aspirin. To assess insulin resistance, the researchers used the estimated glucose disposal rate (eGDR), a validated surrogate marker calculated based on waist circumference, hypertension status, and glycated hemoglobin (HbA1c) levels. A cut-off of 8 mg/kg/min was used to categorize patients into high insulin resistance (eGDR < 8) and low insulin resistance (eGDR ≥ 8) groups.

The primary efficacy outcome was recurrent stroke (ischemic or hemorrhagic) within 90 days. The primary safety outcome was severe or moderate bleeding based on the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) criteria.

Key Findings: Does Insulin Resistance Dictate Treatment Success?

Among the 4,954 patients, 63.0% (n=3122) were classified as having high insulin resistance, while 37.0% (n=1832) had low insulin resistance. The baseline characteristics reflected the metabolic burden of the high-IR group, who were more likely to have higher BMIs and a higher prevalence of traditional cardiovascular risk factors.

Efficacy Outcomes

The most striking finding was the significant interaction between insulin resistance status and the efficacy of the antiplatelet regimen (p for interaction = 0.01). In patients with low insulin resistance, ticagrelor-ASA was markedly more effective than clopidogrel-ASA, reducing the risk of recurrent stroke by nearly half (3.9% vs. 7.8%; Hazard Ratio [HR] 0.52, 95% CI 0.34 to 0.79).

In contrast, for patients with high insulin resistance, the benefit of ticagrelor vanished. The stroke recurrence rate was identical in both the ticagrelor and clopidogrel arms (7.7% vs. 7.7%; HR 0.96, 95% CI 0.74 to 1.24). Interestingly, the analysis showed that the benefit of ticagrelor over clopidogrel increased continuously as insulin resistance decreased (p for interaction = 0.03), suggesting a gradient effect rather than a simple threshold.

The Diabetes Paradox

Crucially, the researchers found that these results were consistent regardless of whether the patients had a formal diagnosis of diabetes (p for interaction = 0.3). This suggests that insulin resistance itself, rather than just hyperglycemia or the clinical label of diabetes, is the primary driver of antiplatelet non-responsiveness in this population. It highlights the utility of eGDR as a more nuanced metabolic marker than blood glucose or HbA1c alone.

Safety Outcomes

Safety is a paramount concern when using potent antiplatelet agents like ticagrelor. In this analysis, the rates of severe or moderate bleeding within 90 days were low and did not differ significantly between the treatment groups or across insulin resistance categories (p for interaction = 0.8). This indicates that while high insulin resistance may limit the efficacy of ticagrelor, it does not appear to disproportionately increase the risk of major bleeding complications in this specific minor stroke/TIA population.

Expert Commentary: Mechanistic Insights and Clinical Implications

The finding that high IR blunts the efficacy of ticagrelor, even in patients who are genetically predisposed to clopidogrel resistance, is clinically provocative. Ticagrelor is a direct-acting P2Y12 inhibitor that does not require the hepatic activation step that fails in CYP2C19 LOF carriers. Therefore, the lack of superiority in high-IR patients cannot be attributed to pharmacogenomic factors. Instead, it likely stems from the biology of the platelet itself in a metabolically deranged environment.

Insulin resistance creates a pro-thrombotic milieu characterized by increased systemic inflammation, oxidative stress, and impaired nitric oxide bioavailability. Platelets in IR patients often exhibit increased surface expression of P2Y12 receptors and alternative activation pathways that may bypass the inhibition provided by standard P2Y12 blockers. Furthermore, IR is associated with higher levels of reticulated (immature) platelets, which are larger, more active, and potentially more resistant to antiplatelet therapy.

From a health policy and clinical practice perspective, these results suggest that we may need to move beyond “one-size-fits-all” or even “genotype-only” strategies for antiplatelet selection. If insulin resistance biomarkers like eGDR can identify patients who will not benefit from the more expensive and twice-daily ticagrelor regimen, it could lead to more cost-effective and personalized care.

Conclusion: Moving Toward Precision Secondary Prevention

The post hoc analysis of the CHANCE-2 trial provides robust evidence that insulin resistance is a critical modifier of the therapeutic response to DAPT in stroke patients with CYP2C19 LOF mutations. While ticagrelor remains a superior choice for many, its edge over clopidogrel is lost in the face of high metabolic risk.

Future research should focus on whether intensifying antiplatelet therapy or adding metabolic interventions (such as GLP-1 receptor agonists or more aggressive statin therapy) can overcome the increased stroke risk in high-IR patients. For now, clinicians should consider insulin resistance as a vital component of the clinical profile when determining the optimal secondary prevention strategy for minor stroke and TIA.

Funding and Trial Registration

The CHANCE-2 trial was supported by grants from the National Natural Science Foundation of China and the Ministry of Science and Technology of the People’s Republic of China. ClinicalTrials.gov Identifier: NCT04078737.

References

1. Zhao J, Tian X, Yang X, et al. Effect of insulin resistance on ticagrelor-versus clopidogrel-based dual antiplatelet therapy for secondary prevention of stroke in carriers of CYP2C19 loss-of-function mutations. CMAJ. 2026;198(2):E36-E43. doi:10.1503/cmaj.241581.

2. Wang Y, Chen W, Lin Y, et al. Ticagrelor versus Clopidogrel in CYP2C19 Loss-of-Function Carriers with Stroke or TIA. N Engl J Med. 2021;385(27):2520-2530.

3. Johnston SC, Amarenco P, Albers GW, et al. Ticagrelor and Aspirin or Aspirin Alone in Acute Ischemic Stroke or TIA. N Engl J Med. 2020;383(3):207-217.