Retatrutide yields average 28% weight loss

Eli Lilly said on May 21 that retatrutide, its experimental once-weekly obesity drug, met the main goals of the phase 3 TRIUMPH-1 trial in adults with obesity or overweight and at least one weight-related condition, without diabetes. The company said people given the highest 12 mg dose lost an average of 70.3 pounds, or 28.3% of body weight, over 80 weeks. (investor.lilly.com) Lilly described retatrutide as a first-in-class medicine that targets GIP, GLP-1 and glucagon receptors, setting it apart from current single- and dual-pathway obesity drugs. The topline data place retatrutide among the strongest obesity-drug results reported so far, based on Lilly’s summary of the study. CNBC reported the comparison used patients who remained on treatment, while Lilly said placebo patients lost 2.2% on the same measure. (prnewswire.com) The company has not yet published full TRIUMPH-1 data in a peer-reviewed journal. ### How much weight did people lose at the top dose? The 12 mg arm produced a mean weight reduction of 28.3% at 80 weeks, Lilly said, equal to 70.3 pounds on average. Lilly also said 45.3% of participants on 12 mg lost at least 30% of their body weight, and 65.3% finished with a body mass index below 30. Lower doses also produced large losses. (investor.lilly.com) Lilly said participants on 9 mg lost an average of 64.4 pounds, or 25.9%, and those on 4 mg lost 47.2 pounds, or 19.0%, at 80 weeks. ### What makes retatrutide different from current GLP-1 drugs? Scientific American and Today reported that retatrutide mimics three gut-related hormone pathways — GIP, GLP-1 and glucagon — rather than only GLP-1 or GLP-1 plus GIP. (cnbc.com) Lilly used the same description in its trial announcement, calling the drug a triple hormone receptor agonist. Pharmacy Times said the glucagon component may increase energy expenditure alongside appetite suppression from incretin signaling. That mechanism is one reason outside coverage has described retatrutide as a next-generation obesity medicine, though the drug remains investigational. (investor.lilly.com) ### What did Lilly say about side effects? Lilly said the most common adverse events were gastrointestinal and were generally mild to moderate in severity. (investor.lilly.com) Those events occurred mainly while doses were being increased and were similar to side effects seen with incretin-based therapies, the company said. AJMC, citing the topline results, reported discontinuation rates due to adverse events of 4.1% at 4 mg, 6.9% at 9 mg and 11.3% at 12 mg, compared with 4.9% for placebo. (today.com) Lilly’s release did not provide the same level of side-effect detail in the summary surfaced by search results, so those figures should be read as secondary reporting on the topline data. ### Did the trial show weight loss continuing beyond 80 weeks? (pharmacytimes.com) Lilly said participants with a baseline BMI of at least 35 who entered a study extension and stayed on 12 mg reached average weight loss of 85.0 pounds, or 30.3%, at 104 weeks. Pharmacy Times reported the extension suggested weight loss had not yet plateaued in that subgroup. (investor.lilly.com) That extension finding came from a subset of participants, not the full 80-week primary analysis. The main phase 3 headline remains the 28.3% average loss at 80 weeks in the 12 mg group. ### What happens next for retatrutide? Lilly said retatrutide is still investigational and has not been approved by the U.S. (ajmc.com) Food and Drug Administration. The company said more phase 3 trials in obesity and type 2 diabetes are expected to finish in 2026, providing the next set of data that could support regulatory filings. May 21 marked Lilly’s release of only topline TRIUMPH-1 results. (morningstar.com) The next milestones are full data presentation, publication and any filing timeline the company gives regulators. (prnewswire.com) (investor.lilly.com)