INDIANAPOLIS, December 12, 2025: Eli Lilly and Co. announced that its next-generation obesity drug, retatrutide, achieved significant weight loss and reduced knee pain in a late-stage Phase 3 trial, underscoring its potential as a major advance in obesity and osteoarthritis treatment. The TRIUMPH-4 study evaluated retatrutide, a triple-hormone receptor agonist that activates GLP-1, GIP, and glucagon pathways, in adults with obesity and knee osteoarthritis. Participants receiving the highest dose of the drug lost an average of 28.7 percent of their body weight after 68 weeks of treatment, equivalent to approximately 71 pounds.
Those receiving placebo lost an average of 2.1 percent during the same period. In addition to substantial weight reduction, participants reported marked improvements in knee pain and joint function. Retatrutide-treated patients experienced up to a 75.8 percent reduction in pain scores, with more than one in eight becoming pain-free by the end of the study. The findings highlight the compound’s potential to address both metabolic and musculoskeletal challenges linked to obesity.
The trial enrolled adults with a body mass index of 30 or higher who also had knee osteoarthritis. None of the participants had diabetes. The treatment groups received two dosing regimens of retatrutide combined with standard diet and exercise support. The drug met all primary and key secondary endpoints, including reductions in body weight and osteoarthritis pain intensity. Lilly reported that the safety and tolerability profile of retatrutide was consistent with other incretin-based therapies.
Retatrutide delivers major weight loss in phase 3 study
The most common side effects included nausea, diarrhea, constipation, and vomiting, particularly at higher doses. Some participants discontinued the medication because of gastrointestinal symptoms or excessive weight loss. Despite these dropouts, the company said the majority of participants completed the full course of therapy. The announcement positions Eli Lilly as a continued leader in the expanding obesity-treatment market. The company already markets tirzepatide, sold under the brand names Zepbound and Mounjaro, which has shown significant success in weight management and diabetes care.
Retatrutide’s trial results suggest a stronger overall effect on weight reduction, with added benefits for patients suffering from joint pain due to obesity-related osteoarthritis. According to Lilly, the TRIUMPH-4 trial is one of eight ongoing Phase 3 studies evaluating retatrutide for various obesity-related conditions, including metabolic disorders. Additional data from these studies are expected through 2026. The company has not yet disclosed when it plans to submit the drug for regulatory approval.
Results highlight new era of obesity and joint care treatment
The obesity drug market has grown rapidly in recent years, driven by strong demand for GLP-1 and GIP-based therapies that deliver both weight loss and metabolic benefits. Analysts estimate that the global market for such treatments could exceed $100 billion annually by the end of the decade, as pharmaceutical firms race to develop more effective multi-hormone agents. Lilly said the latest data will be presented at upcoming medical conferences and submitted for publication in a peer-reviewed journal.
The company emphasized that the results reinforce the scientific approach of targeting multiple hormonal pathways to achieve sustained weight loss and broader health improvements in people with obesity. Retatrutide’s performance in the late-stage trial marks one of the strongest outcomes seen in obesity treatment to date. The combination of extensive weight loss and pain relief offers a potential new therapeutic option for patients struggling with both obesity and osteoarthritis, conditions that frequently overlap and compound health burdens worldwide. – By Content Syndication Services.