The rivalry between Novo Nordisk and Eli Lilly — the two giants battling for dominance of the booming GLP-1 market — took center stage this week at the European Association for the Study of Diabetes (EASD) annual meeting in Milan. On September 29, Novo announced new real-world data suggesting that patients who stayed with its drug Ozempic at a higher dose had a lower risk of major heart-related events than patients who switched to Lilly's rival, Mounjaro.
The findings, from a retrospective analysis of more than 636,000 adults with type 2 diabetes, add a cardiovascular dimension to a debate that has mostly revolved around weight loss and blood sugar. They arrive at a moment of intense competition: analysts expect the US obesity drug market alone to reach between $100 billion and $150 billion by 2030.
What the COMPETE SWITCH CV analysis found
The study, dubbed COMPETE SWITCH CV, looked at adults with type 2 diabetes who were already taking once-weekly semaglutide (Ozempic) at the 1 mg dose. Researchers compared two common real-world strategies when that dose is no longer enough: escalating semaglutide to 2 mg, or switching to tirzepatide (Mounjaro) at doses of up to 15 mg. Tirzepatide is a dual GIP/GLP-1 receptor agonist, a newer class of drug that has shown particularly strong results for weight loss.
In the analysis of 636,525 adults, treatment patterns shifted over time. Within 365 days of their first prescription, 67.2 percent of patients had remained on Ozempic 1 mg, while 29.2 percent had either increased to Ozempic 2 mg or switched to Mounjaro. By the 720-day follow-up, 57.4 percent were still on the 1 mg dose, 36.9 percent had escalated to 2 mg, and 5.7 percent had switched to Mounjaro.
The key result: patients who escalated to semaglutide 2 mg were associated with a statistically significant 6 percent lower risk of major adverse cardiovascular events — MACE — than those who switched to tirzepatide. MACE in this analysis included all-cause death, heart attack (myocardial infarction) and stroke. The adjusted hazard ratio was 1.06 for the switch group versus the escalation group, with a 95 percent confidence interval of 1.04 to 1.08 and a p-value of 0.005.
"For people with type 2 diabetes, switching therapies or adjusting dosages are often necessary to achieve glycemic control — still, cardiovascular risk should also remain an important consideration," said Michael Radin, MD, executive medical director at Novo Nordisk. "These real-world findings can help provide insights into how intensification strategies may affect cardiovascular outcomes as an important factor in patient care."
A decision point doctors face every day
The analysis addresses a genuinely common dilemma in clinical practice: when a patient tolerating a GLP-1 drug has not yet reached their treatment goals, should the doctor intensify the current therapy or switch to a different one?
"Treatment intensification is a common challenge we face in clinical practice, particularly for adults with type 2 diabetes who have not yet met their treatment goals but are otherwise tolerating their current regimen well," said Kathryn S. Tierney, MSN, APRN, FNP-BC, FAANP, of Middlesex Health MultiSpecialty Group in Middletown, Connecticut. "The analysis reinforces the importance of considering cardiovascular outcomes, alongside glycemic management, when making treatment decisions."
The cardiovascular findings build on an earlier analysis of the same dataset, presented at the American Diabetes Association Scientific Sessions in June 2026, which examined blood sugar (HbA1c) and weight-loss outcomes. Notably, the heart data arrived about a month after US regulators approved tirzepatide to reduce cardiovascular risk in adults with type 2 diabetes — meaning both drugs now carry cardiovascular claims of different kinds, sharpening the question of how they compare.
Dueling datasets in Milan
Novo's presentation was not the only headline from EASD. Lilly countered with its own comparisons, including data on its oral GLP-1 pill versus Novo's weight-loss pill Wegovy in type 2 diabetes, and an indirect assessment linking its obesity injectable Zepbound to greater weight loss than Novo's high-dose Wegovy format. As industry press noted, neither company's presentations were strict randomized head-to-head trials — they were real-world analyses and indirect comparisons, each sponsored by a party with a commercial stake in the outcome.
That context matters. Retrospective real-world evidence can reflect the messiness of actual practice — diverse patients, imperfect adherence, real prescribing patterns — but it cannot randomize, and it cannot fully eliminate the possibility that the patients who escalated their dose differed in important ways from those who switched drugs. The findings are best read as one more data point for doctors and patients to weigh, not as a final verdict on which drug protects the heart better.
What it means for patients
For the millions of people taking GLP-1 medications, the practical message is less about brand loyalty than about the questions worth asking at the next appointment. Cardiovascular risk is a central concern in type 2 diabetes — heart disease remains one of the leading causes of death in this population — so treatment decisions that consider heart outcomes alongside weight and blood sugar make sense.
Patients should not change doses, switch medications or start a new drug based on conference presentations. Any change to a diabetes regimen should be discussed with the prescribing doctor, who can weigh the full picture: blood sugar control, weight, cardiovascular risk, side effects, cost and insurance coverage. This article summarizes published research and news reporting; it is not medical advice.
What is certain is that the GLP-1 story is entering a more nuanced phase. The first chapter was about dramatic weight loss. The next chapters — heart outcomes, long-term safety, oral formulations, and how these drugs compare head to head — will determine how these medicines are used for decades to come. This week's data from Milan is one early page of that story.
Competition in the space is only intensifying. Both companies launched oral GLP-1 pills for weight management earlier in 2026, a development analysts say has begun to shift market share dynamics in the key US market, and a wave of rival incretin drugs is working through development pipelines. For patients, more options should eventually mean more tailored treatment — but also more conflicting claims to navigate, making independent, peer-reviewed evidence all the more valuable.
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