Eli Lilly posts 28% weight loss

Eli Lilly said on May 21 that its experimental obesity drug retatrutide helped adults with obesity lose an average of 28.3% of their body weight over 80 weeks in a late-stage trial. The company said the result came in TRIUMPH-1, a Phase 3 study in adults with obesity or overweight plus at least one weight-related condition, excluding diabetes. Reuters reported the data could support a regulatory filing and a potential launch next year, if approved. Lilly has not yet published the full dataset in a peer-reviewed journal. ### How big was the weight loss in the trial? Lilly said participants taking the highest 12-milligram dose lost 70.3 pounds on average, or 28.3% of body weight, over 80 weeks. The company said patients on the 9-milligram dose lost 64.4 pounds, or 25.9%, and those on 4 milligrams lost 47.2 pounds, or 19.0%. (finance.yahoo.com) More than 45% of participants on the 12-milligram dose lost at least 30% of their body weight, Lilly said. The company also said 65.3% of patients on that dose fell below a body-mass index of 30 by week 80, and a pre-specified extension in participants with baseline BMI of at least 35 showed average weight loss of 30.3% at 104 weeks. (investor.lilly.com) ### What is retatrutide, and how is it different from current obesity drugs? Retatrutide is a once-weekly injectable drug that activates three hormone receptors: GLP-1, GIP and glucagon, according to Lilly and Reuters. Lilly’s currently marketed obesity drug Zepbound, known chemically as tirzepatide, targets GLP-1 and GIP but not glucagon. (investor.lilly.com) Kenneth Custer, Lilly’s president of cardiometabolic health, told Reuters that the level of weight loss crossed a threshold “historically been associated with bariatric surgery.” Ania Jastreboff of Yale School of Medicine, the trial’s lead investigator, said in Lilly’s release that people with severe obesity on the highest dose lost about 30% of body weight over two years. (investor.lilly.com) ### What did Lilly say about side effects and dropouts? Lilly said the safety profile was generally consistent with incretin-based therapies, a class that includes nausea, vomiting, diarrhea and constipation. Reuters also reported that dysesthesia, an abnormal skin sensation, occurred in 12.5% of patients on the 12-milligram dose versus 0.9% on placebo. (finance.yahoo.com) Discontinuations due to adverse events rose with dose, according to reports summarizing Lilly’s topline results. They were 4.1% at 4 milligrams, 6.9% at 9 milligrams and 11.3% at 12 milligrams, compared with 4.9% on placebo. Lilly said the 4-milligram arm, which used a single escalation step, showed a lower observed discontinuation rate due to adverse events than placebo. (finance.yahoo.com) ### Who was in TRIUMPH-1? TRIUMPH-1 enrolled 2,339 adults with obesity or overweight, according to Lilly and trial listings. The study tested 4-milligram, 9-milligram and 12-milligram doses against placebo in adults without diabetes who also had at least one weight-related comorbidity. (empr.com) ClinicalTrials.gov lists TRIUMPH-1 under identifier NCT05929066 and describes it as active, not recruiting. The registry says the study is evaluating efficacy and safety in obesity and overweight, including subsets involving knee osteoarthritis and obstructive sleep apnea. ### What happens next before doctors or patients can use it? Lilly said additional TRIUMPH-1 results will be presented at the American Diabetes Association’s 86th Scientific Sessions in June 2026. (ajmc.com) Reuters reported Custer said the company hopes to launch the drug next year, which would require regulatory review first. (clinicaltrials.gov) The next public milestone is the ADA meeting in New Orleans from June 5 to June 9, 2026, where Lilly has said it will share more detailed data from TRIUMPH-1 alongside other cardiometabolic pipeline results. (professional.diabetes.org) (investor.lilly.com)