SELECT Trial: Semaglutide CV Outcomes in Obesity Without Diabetes

Trial design

SELECT (NCT03574597) was a randomized, double-blind, placebo-controlled trial conducted at 804 sites across 41 countries. Eligible participants were adults aged 45 or older with established cardiovascular disease (prior myocardial infarction, stroke, or peripheral artery disease) and BMI ≥27 kg/m², without diabetes. Type 2 diabetes was an exclusion criterion to specifically test the obesity-only population.

Participants were randomized 1:1 to semaglutide 2.4 mg weekly (titrated over 16 weeks) or matching placebo, both on top of standard cardiovascular care. Mean baseline characteristics: age 61.6 years, 27.7% female, 12.5% with prior stroke, 76.7% prior myocardial infarction, 56.3% on beta-blocker, 70.7% on statin. Mean BMI was 33.4 kg/m²; mean HbA1c was 5.8% (pre-diabetes range)¹.

Primary outcome

The primary endpoint — a composite of cardiovascular death, nonfatal MI, or nonfatal stroke (MACE-3) — occurred in 569 participants (6.5%) in the semaglutide group versus 701 (8.0%) with placebo. Hazard ratio 0.80 (95% CI 0.72-0.90; P<0.001). Number needed to treat over the median 33-month exposure period: approximately 67.

The benefit emerged within the first 12 months and continued accumulating throughout follow-up. The curves separated early and continued to diverge, suggesting that benefit extends with longer treatment duration rather than reflecting a one-time effect.

Component endpoints

Cardiovascular death: HR 0.85 (95% CI 0.71-1.01; P=0.07; not statistically significant)

Nonfatal myocardial infarction: HR 0.72 (95% CI 0.61-0.85)

Nonfatal stroke: HR 0.93 (95% CI 0.74-1.15; not statistically significant)

All-cause mortality: HR 0.81 (95% CI 0.71-0.93; P=0.003)

The strongest signal was in nonfatal MI (28% reduction), consistent with the SUSTAIN-6 pattern in T2D. Cardiovascular death showed a numerical reduction but did not reach statistical significance in this trial design. All-cause mortality reduction was significant¹.

Weight loss in SELECT

Mean weight loss at 104 weeks was 9.4% with semaglutide versus 0.9% with placebo. This is less than STEP-1 weight loss (14.9% at 68 weeks in nondiabetic adults without prior CVD); SELECT participants were older, more likely to be men, and on more concomitant medications, which may explain the difference.

Importantly, mediation analyses suggested that only approximately 30% to 50% of the cardiovascular benefit could be attributed to weight loss alone. Additional weight-loss-independent mechanisms — improved insulin sensitivity, anti-inflammatory effects, blood pressure reduction, improvements in lipid profile, and possibly direct cardiac effects via GLP-1 receptors — appear to contribute to the cardiovascular benefit.

Subgroup analyses

Cardiovascular benefit was consistent across pre-specified subgroups: age, sex, race, baseline BMI, baseline HbA1c, baseline blood pressure, baseline LDL, type of prior cardiovascular event, and concomitant medication use. No subgroup showed clearly attenuated or absent benefit, suggesting that the result generalizes to most patients meeting the inclusion criteria.

Patients with baseline HbA1c in the pre-diabetes range (5.7% to 6.4%) had marginally greater benefit than those with normal HbA1c, possibly reflecting underlying metabolic dysfunction. Patients with very high baseline BMI (≥40 kg/m²) had benefit similar to those with lower BMI; the relative risk reduction was consistent across the BMI spectrum.

Implications for clinical practice

SELECT extends the indication for semaglutide cardiovascular benefit beyond type 2 diabetes (SUSTAIN-6) to the much larger population of adults with obesity and established cardiovascular disease without diabetes. The FDA updated Wegovy labeling in March 2024 to include cardiovascular risk reduction as an indication.

The implications are substantial: an estimated 6.6 million U.S. adults meet SELECT inclusion criteria (obesity + established CVD without diabetes). If even 20% of this population were treated with semaglutide, the population-level reduction in cardiovascular events would be on the order of 30,000 to 60,000 events per year.

Cost and access remain the rate-limiting factors. Branded Wegovy at $1,300+ per month substantially exceeds insurance willingness-to-pay thresholds for cardiovascular prevention in many cases. Compounded semaglutide and emerging generic supply may make widespread implementation more feasible.

Related editorial coverage

• STEP-1 trial: semaglutide for obesity
• SUSTAIN-6 trial: semaglutide CV outcomes in T2D
• Semaglutide peptide profile

Frequently asked questions

Did the SELECT trial include patients with diabetes?

No. SELECT specifically excluded patients with type 2 diabetes to demonstrate cardiovascular benefit in the obesity-only population. Patients with pre-diabetes (HbA1c 5.7% to 6.4%) were included. Cardiovascular benefit for semaglutide in T2D was previously established in SUSTAIN-6¹.

What does SELECT mean for someone considering Wegovy for weight loss?

SELECT provides high-quality randomized evidence that semaglutide 2.4 mg reduces cardiovascular events in adults with obesity and established cardiovascular disease. This extends Wegovy's benefit beyond weight loss alone. For patients with obesity who also have established cardiovascular disease, semaglutide offers benefit that few other weight-loss medications can match.

Did weight loss explain all of the cardiovascular benefit?

No. Mediation analyses suggest only 30% to 50% of the cardiovascular benefit can be attributed to weight loss. Additional mechanisms — anti-inflammatory effects, improved insulin sensitivity, lipid changes, and possibly direct cardiac receptor effects — appear to contribute substantially.

Did SELECT change the FDA label for semaglutide?

Yes. In March 2024, the FDA approved a label update for Wegovy adding cardiovascular risk reduction as an indication in adults with obesity and established cardiovascular disease. This is the first non-diabetes cardiovascular indication for a GLP-1 receptor agonist.