GLP-1 retatrutide has shown “powerful weight loss” effects in a “pivotal” phase three trial, named Triumph-1, Eli-Lilly announced on May 21.
The trial investigated the “efficacy and safety of retatrutide” to treat adults with obesity and “at least one weight-related comorbidity and without diabetes”.
It found that at the “80 weeks” mark, all doses of retatrutide, which included 4 mg, 9 mg, and 12 mg, met the “primary and key secondary endpoints for obesity” and so delivered “clinically meaningful weight loss”.
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Patients on 12mg of the drug lost “an average of 70.3 lbs (28.3%) over 80 weeks” and those on 9 mg lost “64.4 lbs (25.9%)”.
The 12 mg dose of retatrutide saw 65.3% of participants attain a BMI of 30 or under and fell “under the threshold for obesity at 80 weeks”.
A high of 45.3% of participants ended the trial with “30%” or higher levels of weight loss, which Eli-Lilly has said is “a level long associated with bariatric surgery”.
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People taking part in a study extension who had a BMI of 35 or over saw a “85.0 lbs (30.3%) weight loss at 104 weeks”.
With a 4 mg dose of the drug, “an average of 47.2 lbs (19.0%) at 80 weeks” was lost “with a lower observed discontinuation rate due to adverse events”.
“Highly impactful”
Yale medical school Professor of medicine and pediatrics and director of the Yale Obesity Research Center, Ania Jastreboff said “treatment with retatrutide not only resulted in robust weight reduction” but also improved “assessed cardiometabolic health measures”.
She also described the drug’s potential for patients in her obesity clinic to be a “highly impactful future tool to treat their obesity and transform their health trajectory”.
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In January, the Medicines and Healthcare products Regulatory Agency (MHRA) revealed that 5,851 “counterfeit or unlicensed” weight loss jabs were seized by the organisation in 2025, with 4,000 found to be retatrutide, which is still unlicensed in the UK and around the world.
The Committee of Advertising Practice (CAP) said in October, that it was investigating customers buying unlicensed weight loss jabs in the UK.
These included reports of people buying retatrutide from pharmacies, which Taylor Meanwell from CAP said was “being looked at”, when questioned at the 2025 Pharmacy Show in Birmingham.
