Eli Lilly and Co. (LLY) just dropped some impressive numbers from its Phase 3 obesity trial. The drugmaker reported Thursday that its experimental triple-hormone drug retatrutide helped patients lose up to 28.3% of their body weight after 80 weeks of treatment. That's an average of 70.3 pounds for those on the highest dose.
Retatrutide is what's called a triple hormone receptor agonist — it targets GIP, GLP-1, and glucagon pathways all at once. Think of it as a souped-up version of the GLP-1 drugs you've been hearing about, but with two extra levers to pull. The study looked at adults with obesity or overweight who also had at least one weight-related condition, but it excluded people with diabetes.
Higher Doses, Bigger Results
The trial tested three doses: 4 mg, 9 mg, and 12 mg. And the results were clearly dose-dependent. Patients on the 12 mg dose lost an average of 28.3% of their body weight (70.3 pounds). Those on 9 mg lost 25.9% (64.4 pounds), and the 4 mg group lost 19% (47.2 pounds). All doses hit the study's primary and key secondary endpoints, Lilly said.
Perhaps more striking: 65.3% of participants on the 12 mg dose achieved a body mass index below 30 — that's the cutoff for obesity. Even among those who started with class 3 obesity (BMI of 40 or higher), 37.5% moved below the obesity threshold. That's a meaningful shift for people who started at a very high weight.
Two-Year Data Shows Sustained Weight Loss
Lilly also ran a blinded extension study for participants with a BMI of at least 35. Those who stayed on the 12 mg dose for a full 104 weeks (about two years) lost an average of 85 pounds, or 30.3% of their body weight. That's a lot of weight, and it suggests the drug keeps working over time.
For the treatment regimen estimand — a statistical measure that accounts for people who stopped taking the drug — weight reductions at 80 weeks were 17.6% for 4 mg, 23.7% for 9 mg, and 25% for 12 mg, versus just 3.9% for placebo. At 104 weeks, those numbers improved further: 25.7%, 28.7%, and 29.9% for the respective dose groups that were allowed to titrate up to a maximum tolerated dose.
More Than Just Weight Loss
Retatrutide also showed benefits beyond the scale. Lilly said it improved several cardiovascular risk markers, including waist circumference, triglycerides, systolic blood pressure, and high-sensitivity C-reactive protein (a marker of inflammation). That's important because obesity drugs need to show they're not just making people lighter, but also healthier.
Lilly plans to present additional data from TRIUMPH-1 at the upcoming American Diabetes Association Scientific Sessions. Later this year, we'll also see results from TRIUMPH-2 (in patients with Type 2 diabetes) and TRIUMPH-3 (in patients with cardiovascular disease). Those will be key to understanding how retatrutide stacks up in more complex patient populations.
Investors seemed pleased: Lilly shares were up 2.16% at $1,040.84 at the time of publication Thursday.
