GLP-1 Receptor Agonists and Heart Disease: What the Evidence Actually Shows

What did the SELECT trial show?

SELECT enrolled 17,604 adults aged 45 or older with preexisting cardiovascular disease and a body-mass index of 27 or higher, none of whom had diabetes. They received semaglutide 2.4 mg once weekly or placebo [1].

Over a mean follow-up of 39.8 months, the primary endpoint - cardiovascular death, nonfatal heart attack or nonfatal stroke - occurred in 569 of 8,803 people taking semaglutide (6.5%) and 701 of 8,801 taking placebo (8.0%). That is a hazard ratio of 0.80 (95% CI 0.72 to 0.90), a 20% relative reduction [1]. The Wegovy cardiovascular indication rests on this result [2].

The population matters as much as the number. Every participant had established cardiovascular disease, and nobody had diabetes. This is evidence for people who already have heart or vascular disease.

Which GLP-1 products carry a cardiovascular indication?

The labels differ in both wording and population.

Wegovy injection and Wegovy tablets are indicated to reduce the risk of major adverse cardiovascular events - cardiovascular death, nonfatal myocardial infarction or nonfatal stroke - in adults with established cardiovascular disease and either obesity or overweight [2].

Ozempic injection and Ozempic tablets (oral semaglutide) carry cardiovascular risk reduction in adults with type 2 diabetes and established cardiovascular disease [3][10]. Victoza carries the same for adults with type 2 diabetes and established cardiovascular disease [4]. Trulicity goes slightly wider: cardiovascular risk reduction in adults with type 2 diabetes who have established cardiovascular disease or multiple cardiovascular risk factors [5].

Semaglutide and liraglutide in type 2 diabetes: two outcome trials

SUSTAIN-6 randomized 3,297 adults with type 2 diabetes to semaglutide 0.5 mg or 1 mg weekly or placebo for 104 weeks. At baseline, 83.0% had established cardiovascular disease, chronic kidney disease, or both. The primary composite outcome occurred in 6.6% on semaglutide and 8.9% on placebo (hazard ratio 0.74, 95% CI 0.58 to 0.95) [6]. The trial's primary hypothesis was noninferiority, with a margin of 1.8 on the upper confidence bound [6].

LEADER randomized 9,340 adults with type 2 diabetes and high cardiovascular risk to liraglutide or placebo, with a median follow-up of 3.8 years. The primary composite outcome occurred in 13.0% on liraglutide and 14.9% on placebo (hazard ratio 0.87, 95% CI 0.78 to 0.97). Cardiovascular death was 4.7% versus 6.0% (hazard ratio 0.78) and death from any cause 8.2% versus 9.6% (hazard ratio 0.85). Nonfatal heart attack, nonfatal stroke and heart-failure hospitalization were nonsignificantly lower [7].

What about tirzepatide?

Tirzepatide (Mounjaro, Zepbound) activates both GIP and GLP-1 receptors, so it is a dual agonist rather than a pure GLP-1 drug, though it is usually grouped with them [11]. Mounjaro is labeled for type 2 diabetes and Zepbound for weight management and sleep apnea [11][15].

In SURMOUNT-5, 751 adults with obesity but no diabetes received the maximum tolerated dose of tirzepatide or semaglutide for 72 weeks. Weight fell 20.2% on tirzepatide and 13.7% on semaglutide, with waist circumference down 18.4 cm versus 13.0 cm [9]. In SURPASS-2, 1,879 adults with type 2 diabetes received tirzepatide 5, 10 or 15 mg or semaglutide 1 mg for 40 weeks; HbA1c fell 2.01, 2.24 and 2.30 points versus 1.86 points [8]. Neither of these two trials had a heart attack, stroke or cardiovascular death as its primary endpoint [8][9].

What the labels flag in people with heart disease

Boxed warnings differ by product. Wegovy's boxed warning is based on thyroid C-cell tumors seen in rodents. Foundayo's label says orforglipron did not produce tumors in rodents, while the human relevance of GLP-1-receptor-dependent rodent tumors remains undetermined. Both products are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2 [2][12]. Labels also warn about acute pancreatitis, acute gallbladder disease, acute kidney injury from volume depletion, severe gastrointestinal reactions (the drug is not recommended in patients with severe gastroparesis), serious hypersensitivity, and diabetic retinopathy complications in type 2 diabetes [2][12].

Heart rate is monitored for a reason. The Wegovy label reports mean resting heart rate increases of 1 to 4 beats per minute and says to monitor heart rate at regular intervals [2]. Tirzepatide's label reports 1 to 3 beats per minute [11]; the orforglipron (Foundayo) label reports 4 to 5 beats per minute versus 0.5 on placebo [12].

Blood pressure can move too. In the pooled Foundayo weight-management trials, hypotension occurred in 2% of treated patients versus 0.5% on placebo; among Foundayo-treated patients it was more frequent with concomitant antihypertensive therapy (4%) than without (1%) [12].

Do GLP-1 drugs interact with heart medicines?

The class delays gastric emptying, which can change absorption of oral drugs. The Wegovy label advises increased clinical or laboratory monitoring with oral medicines that have a narrow therapeutic index or require clinical monitoring, and notes that semaglutide 1 mg injection did not affect absorption of orally administered medicines in clinical pharmacology trials [2]. The semaglutide tablet increased levothyroxine exposure by 33% [2].

Hypoglycemia risk rises when a GLP-1 drug is combined with insulin or a sulfonylurea, and labels advise considering a lower dose of the insulin or secretagogue at initiation [2][12]. For orforglipron specifically, the label caps the dose at 9 mg with strong CYP3A4 inhibitors, says to avoid strong inducers, and limits simvastatin to 20 mg daily because simvastatin acid exposure doubled [12].

How it is dosed

The Wegovy injection label starts at 0.25 mg once weekly for 4 weeks and escalates every 4 weeks to a maintenance dose of 2.4 mg weekly [2]. The Wegovy tablet label starts at 1.5 mg daily for 30 days and escalates every 30 days to 25 mg daily, the maintenance dose for both cardiovascular risk reduction and weight reduction, and says the tablet is taken on an empty stomach with up to 4 ounces of water, 30 minutes before food or other oral medicines [2]. The Foundayo label starts at 0.8 mg daily and steps up no faster than every 30 days to a maximum of 17.2 mg, with the escalation intended to reduce gastrointestinal reactions [12].

What happens when treatment stops

STEP 4 followed 803 adults who had completed a 20-week semaglutide run-in to 2.4 mg, then continued semaglutide or switched to placebo for 48 weeks. Those who continued lost another 7.9% of body weight; those switched to placebo gained 6.9% [13].

Does the benefit require diabetes?

No - SELECT enrolled people without diabetes, and the Wegovy cardiovascular indication is built on established cardiovascular disease plus obesity or overweight, with no diabetes requirement [2][1].