Four years. About 13,300 people. The longest and largest tirzepatide trial ever run. It did not beat its comparator — and that is the interesting part.
SURPASS-CVOT was a double-blind, randomized, active-comparator noninferiority trial. It enrolled adults with type 2 diabetes, a BMI of at least 25, and established atherosclerotic cardiovascular disease. Roughly 13,300 people were randomized 1:1 to weekly tirzepatide (Mounjaro, titrated up to 15mg) or weekly dulaglutide (Trulicity, 1.5mg). Median follow-up was four years.
Mean age was 64, 29% of participants were women, mean diabetes duration was about 15 years, and baseline HbA1c averaged roughly 8%. Most people were already on other diabetes drugs at entry — around 81% on metformin, about 49% on insulin, and roughly 30% on an SGLT2 inhibitor.
The comparator choice matters. There was no placebo group. Dulaglutide is a GLP-1 receptor agonist already shown in the REWIND trial to reduce cardiovascular events versus placebo, so every participant received an active, proven drug. That is ethically sound in a high-risk population, but it also sets a high bar: tirzepatide was not being compared to nothing.
Tirzepatide was started at 2.5mg and increased by 2.5mg every four weeks — the same stepped titration used in routine practice. The primary endpoint was the first occurrence of cardiovascular death, myocardial infarction, or stroke.
Noninferior, not superior. The trial met its prespecified noninferiority test (p=0.003) but missed superiority (p=0.09). The confidence interval around that 0.92 hazard ratio crossed 1.0 by a small margin. In plain terms: tirzepatide protected hearts at least as well as a drug already known to protect hearts, but the trial could not prove it did better.
Several secondary findings leaned in tirzepatide's favour. An expanded endpoint that also counted coronary revascularization was significantly reduced. All-cause mortality was lower with tirzepatide — a difference the investigators attributed largely to fewer non-cardiovascular deaths rather than fewer cardiac ones. Blood pressure, triglycerides, and other lipid measures also improved more.
More weight loss did not translate into fewer heart attacks. Tirzepatide produced more than twice the weight reduction of dulaglutide, and roughly double the HbA1c drop, yet the primary endpoint gap stayed narrow. Lead investigator Stephen Nicholls has said the cardiovascular benefit of this drug class appears to come from a mix of mechanisms, not from weight loss alone.
Over four years in adults with type 2 diabetes and established heart disease, tirzepatide was noninferior to dulaglutide for cardiovascular death, heart attack, or stroke — 12.2% versus 13.1% — while producing substantially more weight loss and better glycemic control.
Sources: Nicholls SJ, Pavo I, Bhatt DL, et al. Cardiovascular outcomes with tirzepatide versus dulaglutide in type 2 diabetes. New England Journal of Medicine, Dec 17 2025;393:2409-2420 (doi:10.1056/NEJMoa2505928) · American College of Cardiology journal scan, Jan 7 2026. NEJM full text · ACC summary.
Four years is the real story. Most GLP-1 weight-loss trials run 68 to 72 weeks. This one ran roughly four times longer, which is closer to how these drugs are actually used. Sustained benefit over that horizon depends on sustained dosing — 208 consecutive weekly injections, none of them memorable on their own.
Side effects, not efficacy, ended treatment. 13.2% of the tirzepatide group stopped because of adverse events versus 10.1% on dulaglutide, driven mainly by gastrointestinal symptoms. Those symptoms cluster around dose increases. Logging what you felt in the week after each step up gives your prescriber something concrete to work with instead of a vague recollection.
Noninferiority is a real result, not a disappointment. It means clinicians now have two evidence-backed options and can choose on other grounds — weight loss, HbA1c targets, tolerability, cost, and coverage. The trial widened the menu rather than declaring a winner.
Read the population before applying the result. Everyone in SURPASS-CVOT had both type 2 diabetes and existing cardiovascular disease, and Mounjaro is the tirzepatide brand approved for type 2 diabetes. These findings do not automatically transfer to someone taking tirzepatide for weight management alone.
This article summarizes published clinical trial results and a professional-society trial summary for general education. It is not medical advice. Individual results vary, and any decision about starting, switching, adjusting, or stopping any GLP-1 or GIP/GLP-1 medication should be made with a prescriber.