Triple-Hormone Drug Clears Two Phase 3 Trials, With Striking Weight Loss but Uncertain Cardiovascular Benefit

The obesity drug race is moving from “how much weight can be lost” to a harder question: in patients with type 2 diabetes or established cardiovascular disease, can substantial weight loss also improve long-term health outcomes? Lilly announced topline results from two pivotal Phase 3 trials in which the experimental once-weekly injectable retatrutide met the primary weight-loss endpoint in both groups of high-risk adults, completing the core clinical data package for the company’s planned global submissions.

TRIUMPH-2 enrolled 1,152 adults with type 2 diabetes and obesity or overweight, who were randomly assigned to receive 4, 9, or 12 mg of retatrutide or placebo. After 80 weeks of treatment, average body weight decreased by 12.7%, 19.1%, and 20.8% in the three dose groups, respectively, compared with 4.0% in the placebo group; glycated hemoglobin decreased by an average of up to 1.6 percentage points. The trial is registered on ClinicalTrials.gov as NCT05929079 and used a randomized, double-blind, placebo-controlled design, including a subgroup of participants with obstructive sleep apnea.

The other trial, TRIUMPH-3, enrolled 1,949 adults with a body mass index of at least 35 and a history of cardiovascular disease, such as myocardial infarction, stroke, or peripheral artery disease; participants could have type 2 diabetes or not. At 80 weeks, average weight loss was 21.6% and 22.6% in the 9 and 12 mg groups, respectively, compared with 3.2% in the placebo group. The trial is registered as NCT05882045 and compared retatrutide with placebo, with the aim of assessing not only changes in body weight but also safety and cardiovascular events in this vulnerable population.

Retatrutide uses a single molecule to simultaneously activate the GIP, GLP-1, and glucagon receptors, seeking to address multiple pathways—including appetite, blood glucose, and energy metabolism—in a single treatment. Improvements were also observed in triglycerides, non-high-density lipoprotein cholesterol, systolic blood pressure, waist circumference, and high-sensitivity C-reactive protein in the highest-dose group in TRIUMPH-3; however, changes in these risk markers cannot be directly equated with confirmed reductions in myocardial infarction or stroke.

The key uncertainty lies precisely in cardiovascular outcomes. Major cardiovascular events occurred less frequently than expected in both groups: the hazard ratio for the broader five-component composite endpoint was 0.82, with a 95% confidence interval of 0.55 to 1.22; for the stricter three-component endpoint of cardiovascular death, myocardial infarction, or stroke, the hazard ratio was 1.12, with a confidence interval of 0.64 to 1.96. Both crossed the line of no difference, meaning the results neither prove that retatrutide protects the heart nor rule out potential risk. Cardiovascular benefit therefore should not be inferred from the magnitude of weight loss.

The safety profile was dominated by gastrointestinal reactions, including diarrhea, nausea, constipation, decreased appetite, and vomiting. In TRIUMPH-3, discontinuation due to adverse events occurred in 9.8% and 13.5% of participants in the 9 and 12 mg groups, respectively, compared with 4.8% in the placebo group. The data released to date remain company topline results, and the full findings have yet to undergo scrutiny at medical conferences, in peer-reviewed publications, and through regulatory review; as of the most recent update, no formal results had been posted on the trial registry pages. Lilly said it is completing its chemistry, manufacturing, and quality-control data and plans to submit a biologics license application to the U.S. FDA in the first quarter of 2027.