Pharmaceutical giants Novo Nordisk and Eli Lilly locked horns at the European Association for the Study of Diabetes conference in Milan, Italy, releasing competing clinical data on GLP-1 weight-loss injections and pills. The showdown highlights efficacy differences between tirzepatide and semaglutide.
In Plain English: The Clinical Takeaway
- Direct Efficacy Margins: In direct trials, Eli Lilly’s Mounjaro (tirzepatide) generated greater average weight loss than Novo Nordisk’s Wegovy (semaglutide), though indirect comparisons between highest doses show a narrower gap.
- Individualized Tolerability: Discontinuation rates due to side effects remain similar across these major therapies.
Head-to-Head Trial Data and the High-Dose Landscape
The debate over metabolic efficacy intensified following data from the SURMOUNT-5 trial. Researchers evaluated 751 adults with obesity or overweight without diabetes over a 72-week period. Participants receiving Mounjaro achieved an average weight loss of 20.2% of their body weight, or 22.8 kilograms (50.3 pounds). By comparison, participants taking Wegovy recorded a 13.7% reduction, totaling an average loss of 15 kilograms (33.1 pounds).
Novo Nordisk subsequently introduced a higher 7.2-milligram dose of Wegovy, known as Wegovy HD, which triples the standard 2.4-milligram regimen. Eli Lilly responded by evaluating its 15-milligram Mounjaro injection against these higher thresholds. Because a direct head-to-head trial between tirzepatide 15 mg and semaglutide 7.2 mg has not been executed, investigators combined data from separate trials to gauge comparative outcomes.
“In the absence of a head-to-head trial comparing tirzepatide 15 mg against semaglutide 7.2 mg, this indirect comparison offers useful evidence for physicians as they make treatment decisions,” stated Prof. John Wilding of the University of Liverpool, one of the researchers involved in the comparison.
According to that combined dataset, patients taking 15 milligrams of Mounjaro lost an average of 4.5 percentage points more body weight than those on Wegovy HD. Patients taking the 10-milligram dose of Mounjaro surpassed the Wegovy HD cohort by 3.2 percentage points. However, when isolating the timeframe where patients continuously received the medication without interruption, the variance narrowed to 1.8 percentage points and was not statistically significant. Treatment discontinuation rates because of side effects were similar for the two drugs.
| Medication & Regimen | Trial / Data Source | Average Weight Loss (%) |
|---|---|---|
| Mounjaro (Tirzepatide) | SURMOUNT-5 (72 weeks) | 20.2% |
| Wegovy (Semaglutide – Standard) | SURMOUNT-5 (72 weeks) | 13.7% |
| Mounjaro (15 mg) vs. Wegovy HD | Indirect Trial Comparison | +4.5 percentage points advantage for Mounjaro |
Cardiovascular Protection and Real-World Insurance Data
Beyond weight reduction, the Milan conference spotlighted a contest over cardiovascular outcomes in patients diagnosed with type 2 diabetes. Novo Nordisk presented an analysis of U.S. insurance claims covering more than 600,000 adults treated with 1 milligram of Ozempic. The evaluation split patients into two cohorts: approximately 186,000 individuals whose dosage was increased to 2 milligrams, and roughly 23,000 patients who switched from Ozempic to Mounjaro.
The analysis indicated that patients who remained on the higher dose of Ozempic experienced a 6% lower risk of major cardiovascular events, encompassing death from any cause, heart attack, and stroke. “These data may help inform healthcare professionals facing a critical challenge: whether to increase the dosage or switch to another therapy for an adult with type 2 diabetes who is already treated with semaglutide,” explained Dr. Michael Radin, a senior medical director at Novo.
Methodological limitations accompanied the findings. Because clinicians independently determined whether to escalate doses or switch therapies, the patient groups were not randomized and likely differed at baseline. Furthermore, only about 31% of patients who switched to Mounjaro reached a dose of 10 milligrams or more during the follow-up, and Novo itself noted that the data could not establish a definitive causal relationship.
Contrasting insights emerged from an academic study published in Nature Medicine by researchers at Mass General Brigham in Boston. Analyzing U.S. insurance data among type 2 diabetes patients, the team found that both medications reduced the risk of heart attack, stroke, and death, with no statistically significant difference between them.
Eli Lilly countered with data from its randomized SURPASS-CVOT trial, which included more than 13,000 patients with type 2 diabetes and cardiovascular disease. Because participants were randomly assigned to treatment arms, physician selection bias was reduced. Investigators observed that patients taking Mounjaro exhibited an 8% lower risk of major cardiovascular events compared to those taking Trulicity, an older GLP-1 drug.
References
- European Association for the Study of Diabetes (EASD) Annual Meeting Presentations, Milan.
- Nature Medicine, Mass General Brigham comparative cardiovascular study on type 2 diabetes therapies.
- SURMOUNT-5 Clinical Trial Data, Eli Lilly and Company.
- SURPASS-CVOT Cardiovascular Outcomes Trial, Eli Lilly and Company.
