May 21, 2026
In TRIUMPH-1, participants on 12 mg retatrutide lost an average of 70.3 lbs (28.3%) over 80 weeks with 45.3% of participants achieving ≥30% weight loss, a level long associated with bariatric surgery
Individuals with a baseline BMI ≥35 who participated in a study extension continued to lose weight, and achieved up to an average of 85.0 lbs (30.3%) weight loss at 104 weeks
At the 4 mg dose, reached with only a single escalation step, participants lost an average of 47.2 lbs (19.0%) at 80 weeks with a lower observed discontinuation rate due to adverse events vs. placebo
INDIANAPOLIS, May 21, 2026 /PRNewswire/ — Eli Lilly and Company (NYSE: LLY), the maker of Zepbound (tirzepatide) and Foundayo (orforglipron), today announced positive topline results from TRIUMPH-1, a Phase 3 clinical trial evaluating the efficacy and safety of retatrutide, an investigational, first-in-class GIP, GLP-1, and glucagon triple hormone receptor agonist, in adults with obesity or overweight and at least one weight-related comorbidity and without diabetes. At 80 weeks, all doses of retatrutide (4 mg, 9 mg, and 12 mg) met the primary and key secondary endpoints for obesity, delivering clinically meaningful weight loss.
“Obesity is a chronic disease, and people living with obesity deserve treatment options that match the complex biology of their neurometabolic disease,” said Ania Jastreboff, M.D., Ph.D., Professor of Medicine & Pediatrics (Endocrinology) at the Yale School of Medicine, Director of the Yale Obesity Research Center (Y-Weight), and lead investigator. “It was impressive to see that every dose of retatrutide resulted in clinically meaningful weight reduction for nearly all participants, and people with severe obesity on the highest dose lost on average 30% of their body weight over two years. Importantly, treatment with retatrutide not only resulted in robust weight reduction, but also in clear improvements in assessed cardiometabolic health measures. For patients I see in clinic, retatrutide may potentially be a highly impactful future tool to treat their obesity and transform their health trajectory.”
For the primary endpoint, participants taking retatrutide 9 mg and 12 mg lost an average of 64.4 lbs (25.9%) and 70.3 lbs (28.3%), respectively. Those taking the 4 mg dose of retatrutide, with just a single dose escalation step, lost an average of 47.2 lbs (19.0%). Notably, 65.3% of participants taking retatrutide 12 mg achieved a BMI <30, falling under the threshold for obesity at 80 weeks, including 37.5% of those who started with class 3 obesity (BMI ≥40).1 In a pre-specified blinded extension for those with a BMI ≥35, participants who continued on retatrutide 12 mg to 104 weeks lost an average of 85.0 lbs (30.3%).2 Additionally, retatrutide showed significant improvements from baseline across certain cardiovascular risk factors, including waist circumference, non-HDL cholesterol, triglycerides, systolic blood pressure and high-sensitivity C-reactive protein (hsCRP).
TRIUMPH-1 Efficacy Estimand Results3
Primary Endpoint at 80 Weeks
Retatrutide 4 mg
Retatrutide 9 mg
Retatrutide 12 mg
Placebo
Percent change in body weight at 80 weeks from avg. baseline of 112.7 kg (248.5 lbs; BMI of 40.0 kg/m2)i
-19.0%
(-21.4 kg;
-47.2 lbs)
-25.9%
(-29.2 kg;
-64.4 lbs)
-28.3%
(-31.9 kg;
-70.3 lbs)
-2.2%
(-2.5 kg;
-5.5 lbs)
Key Secondary Endpoints at 80 Weeks
Change in waist circumference from baseline of 118.3 cm (46.6 in)
-16.3 cm (-6.4 in)
-21.8 cm (-8.6 in)
-24.1 cm (-9.5 in)
-3.6 cm (-1.4 in)
Percent of participants achieving body weight reduction of ≥25%
27.8 %
52.9 %
62.5 %
2.2 %
Percent of participants achieving body weight reduction of ≥30%
15.3 %
37.9 %
45.3 %
0.5 %
Percent of participants achieving body weight reduction of ≥35%
5.9 %
20.8 %
27.2 %
0.3 %
Pre-specified Extension at 104 Weeksii
Retatrutide 4 mg to MTDiii
Retatrutide 9 mg to MTDiii
Retatrutide 12 mg to MTDiii
Placebo to Retatrutide MTDiii
Percent change in body weight at 104 weeks from avg. baseline of 121.7 kg (268.3 lbs; BMI of 42.8 kg/m2)
-27.9%
(-33.2 kg;
-73.3 lbs)
-29.5%
(-36.6 kg;
-80.7 lbs)
-30.3%
(-38.5 kg;
-85.0 lbs)
-19.2%
(-22.6 kg;
-49.9 lbs)
iPercent body weight reduction with retatrutide 4 mg was a key secondary endpoint.
iiThe extension period enrolled 532 participants with BMI ≥35 at baseline who had completed the main 80-week study and tolerated their assigned dose of medication.
iiiParticipants in the trial extension received retatrutide at a maximum tolerated dose of 9 mg or 12 mg.
“TRIUMPH-1 highlights the importance of options and the potential for retatrutide to help people across various stages of their obesity journey,” said Kenneth Custer, Ph.D., executive vice president and president, Lilly Cardiometabolic Health. “From the 4 mg dose, reaching nearly 20% weight loss with one escalation step, to the 12 mg dose that delivered a level of weight loss long associated with bariatric surgery, retatrutide offers the potential for a patient-centric approach to obesity.4 Together with Zepbound and Foundayo, retatrutide could build on Lilly’s commitment to match treatments to the needs and preferences of patients.”
For the treatment-regimen estimand, each dose level of retatrutide led to improvements across the primary and key secondary endpoints, as well as the pre-specified extension, including:5
- Percent change in body weight at 80 weeks: -17.6% (-19.8 kg; -43.7 lbs; 4 mg); -23.7% (-26.7 kg; -58.9 lbs; 9 mg); -25.0% (-28.2 kg; -62.1 lbs; 12 mg) and -3.9% (-4.4 kg; -9.7 lbs; placebo)
- Percent change in body weight at 104 weeks: -25.7% (-30.6 kg; -67.5 lbs; 4 mg to MTD); -28.7% (-35.6 kg; -78.4 lbs; 9 mg to MTD); -29.9% (-38.1 kg; -83.9 lbs; 12 mg to MTD) and -18.9% (-22.3 kg; -49.1 lbs; placebo to MTD)
