HQ Team
June 17, 2026: Retatrutide, an experimental “triple-agonist” weight-loss drug developed by Eli Lilly, helped patients lose nearly a third of their body weight in a phase 3 clinical trial, with researchers describing results that approach outcomes typically associated with bariatric surgery.
In the TRIUMPH-1 trial, participants taking the highest 12-milligram dose lost an average of 70.3 pounds, or 28.3 per cent of their body weight, over 80 weeks, compared with a 2.2 per cent reduction in the placebo group. Nearly half of patients on the highest dose, 45.3 per cent, achieved a body weight reduction of 30 per cent or more, a threshold historically associated with bariatric surgery outcomes.
A three-hormone approach
Unlike currently approved GLP-1 drugs, retatrutide is designed as a triple-hormone-receptor agonist, activating GLP-1, glucose-dependent insulinotropic polypeptide (GIP) and glucagon simultaneously. Semaglutide, marketed as Wegovy and used in Ozempic, targets only the GLP-1 pathway and produces average weight loss of around 15 per cent. Tirzepatide, sold as Zepbound, targets both GLP-1 and GIP and produces around 21 per cent weight loss on average. Retatrutide’s addition of the glucagon pathway, involved in fat and calorie burning alongside hunger regulation, is believed to account for its larger effect.
“We’ve never had a triple-agonist medication. So, this is completely new, and retatrutide seems to be more potent,” said Dr Cecilia Low Wang, an endocrinologist at UCHealth University of Colorado Hospital and professor at the University of Colorado Anschutz School of Medicine, who is also the former chair of the FDA’s Endocrinologic and Metabolic Drugs Advisory Committee.
Trial design
The TRIUMPH-1 trial randomised 2,339 adults with obesity or overweight, and at least one weight-related health condition but no diabetes, to one of three retatrutide doses or a placebo for 80 weeks. Participants entered the trial with an average baseline body weight of 248.5 pounds and an average body mass index of 40.
Lower doses also produced substantial results: the 9-milligram dose led to average weight loss of 25.9 per cent, or about 64.4 pounds, while the 4-milligram dose, reachable through a single titration step, produced 19 per cent weight loss, or roughly 47.2 pounds. By week 80, 65.3 per cent of participants on the 12-milligram dose had reduced their BMI below 30, the threshold for obesity, including more than a third of those who began the trial with class 3, or severe, obesity.
A prespecified blinded extension among participants with a baseline BMI of 35 or above showed durability of the effect, with those who remained on the 12-milligram dose reaching an average 30.3 per cent body weight reduction, or 85 pounds, by week 104.
Beyond weight loss, the drug was associated with improvements in several cardiometabolic markers, including a 24.1 centimetre reduction in waist circumference and favourable changes in non-HDL cholesterol, triglycerides, systolic blood pressure and a marker of inflammation called high-sensitivity C-reactive protein. Adverse events were largely gastrointestinal, consistent with other incretin-based drugs, and discontinuation rates rose with dose.
Obesity, scale of the problem
Obesity affected an estimated 890 million adults worldwide in 2022, or about 16 per cent of all adults aged 18 and older, according to the World Health Organization. Global obesity prevalence has more than doubled since 1990, and the WHO and World Obesity Federation project the number of adults living with obesity could rise to 1.13 billion by 2030.
Not Yet Approved
Retatrutide has not yet received FDA approval and remains available only to participants in clinical trials. Eli Lilly is expected to submit the drug for regulatory review this year, although no head-to-head trials directly comparing retatrutide with already-approved drugs such as semaglutide or tirzepatide have been completed.
