Semaglutide SELECT Trial: Redefining Cardiovascular Risk in Non-Diabetic Obesity

Written by Adam Maggio | Medically reviewed by Dr. Sarah Chen, PharmD, BCPS

The Semaglutide SELECT trial demonstrated a significant 20% reduction in major adverse cardiovascular events (MACE) in individuals with overweight or obesity and established cardiovascular disease, but without diabetes, highlighting semaglutide's direct cardioprotective effects beyond glycemic control.

The Semaglutide Effects on Cardiovascular Outcomes in People With Overweight or Obesity (SELECT) trial marks a pivotal moment in understanding the comprehensive benefits of GLP-1 receptor agonists beyond glycemic control. This landmark study specifically investigated the impact of once-weekly subcutaneous semaglutide (2.4 mg) on cardiovascular outcomes in a population of individuals with overweight or obesity and established cardiovascular disease (CVD), crucially, without a diagnosis of diabetes. The findings have profound implications for cardiovascular risk management in a large, underserved patient demographic.

The SELECT Trial Design and Key Findings

The SELECT trial was a large, multicenter, randomized, double-blind, placebo-controlled trial involving over 17,600 participants. The primary endpoint was a composite of major adverse cardiovascular events (MACE), defined as cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke. Participants had a body mass index (BMI) of ≥27 kg/m² and established CVD, but no history of diabetes. They were randomized to receive either semaglutide 2.4 mg once weekly or placebo, in addition to standard care.

After a median follow-up of 3.3 years, the SELECT trial demonstrated a statistically significant 20% reduction in the primary MACE endpoint in the semaglutide group compared to placebo [1]. Specifically, a primary cardiovascular event occurred in 6.5% of patients in the semaglutide group versus 8.0% in the placebo group. This translates to an absolute risk reduction of 1.5 percentage points. All three components of the MACE endpoint—cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke—showed consistent reductions, reinforcing the robust nature of semaglutide's cardiovascular benefits.

Mechanisms Beyond Weight Loss and Glycemic Control

One of the most compelling aspects of the SELECT trial's results is that the cardiovascular benefits of semaglutide were observed in a non-diabetic population. This strongly suggests that the cardioprotective effects extend beyond improvements in glycemic control, which is a primary mechanism of GLP-1 RAs in diabetic patients. While semaglutide did induce significant weight loss (an average of 9.4% body weight reduction) and improvements in other cardiometabolic risk factors such as blood pressure and lipid profiles, analyses from the trial indicate that the reduction in MACE was not solely attributable to weight loss alone [2].

Proposed mechanisms for semaglutide's direct cardiovascular benefits include:

Anti-inflammatory effects: GLP-1 RAs have been shown to reduce systemic inflammation, which plays a critical role in atherosclerosis development and progression.

Endothelial function improvement: Semaglutide may improve endothelial function, leading to better vascular health and reduced arterial stiffness.

Direct cardiac effects: GLP-1 receptors are present in the heart, and their activation may lead to direct beneficial effects on myocardial function, although the exact mechanisms are still under investigation.

Blood pressure reduction: Beyond weight loss, GLP-1 RAs can directly lower blood pressure through various mechanisms, including natriuresis and vasodilation.

Clinical Implications and Future Directions

The SELECT trial's findings are transformative for clinical practice. For the first time, a medication primarily known for weight management has definitively shown to reduce hard cardiovascular outcomes in individuals with overweight or obesity and established CVD, independent of diabetes status. This provides a strong rationale for considering semaglutide 2.4 mg in this high-risk population to mitigate cardiovascular events.

This trial underscores the importance of obesity as a direct risk factor for CVD and highlights that targeting obesity with effective pharmacotherapy can yield significant cardiovascular protection. It also opens avenues for broader screening and intervention strategies for individuals with obesity and CVD, moving beyond a sole focus on diabetes as the gateway to GLP-1 RA therapy.

Practical Takeaways

Semaglutide Reduces MACE in Non-Diabetic Obesity: The SELECT trial demonstrated a 20% relative risk reduction in cardiovascular death, non-fatal MI, or non-fatal stroke with semaglutide 2.4 mg in individuals with overweight/obesity and established CVD, without diabetes.

Benefits Beyond Glycemic Control: The cardioprotective effects of semaglutide in this population suggest mechanisms independent of blood glucose lowering, likely involving anti-inflammatory actions, improved endothelial function, and direct cardiac effects.

Obesity as a Direct CVD Risk Factor: The trial reinforces that obesity itself is a significant and modifiable risk factor for CVD, and its treatment can directly improve cardiovascular outcomes.

Expanded Treatment Paradigm: Semaglutide 2.4 mg should be considered for cardiovascular risk reduction in patients with overweight or obesity and established CVD, even in the absence of diabetes.

References

[1] Lincoff, A. M., et al. (2023). Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine. [https://www.nejm.org/doi/full/10.1056/NEJMoa2307563]

[2] Ryan, D. H., et al. (2024). Long-term weight loss effects of semaglutide in obesity and cardiovascular disease in the SELECT trial. Nature Medicine. [https://www.nature.com/articles/s41591-024-02996-7]