In this articleLLYFollow your favorite stocksCREATE FREE ACCOUNTThe Eli Lilly logo appears on the company’s office in San Diego, California, U.S., Nov. 21, 2025.Mike Blake | ReutersEli Lilly on Thursday said its next-generation obesity drug delivered what appears to be the highest weight loss yet in a late-stage trial while reducing knee arthritis pain, clearing the first of several upcoming studies on the weekly injection. The highest dose of the drug helped patients with obesity and a type of knee arthritis lose an average of 23.7% of their body weight at 68 weeks, when analyzing all participants, including those who discontinued treatment. The company said some patients lost so much weight that they decided to drop out of the trial. When evaluating only patients who stayed on the drug – essentially the best-case scenario – the highest dose delivered 28.7% weight loss on average. “It’s incredible,” said Dr. Caroline Apovian, co-director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital. “Now, we have a drug that rivals the weight loss benefits of surgery.”Apovian said Eli Lilly appears to be positioning the drug strategically for people with severe obesity, or a body mass index above 35 or 40. She noted that the company said 84% of patients in the trial had a BMI above that number in the trial.Shares of Eli Lilly rose more than 3% on Thursday. It is the first late-stage data on retatrutide, which works differently from existing injections and appears to be more effective. Eli Lilly is betting big on retatrutide as the next pillar of its obesity portfolio after its weight loss injection Zepbound and its upcoming pill. But it’s still unclear when the drug could enter the market. It’s a critical part of the drugmaker’s plan to maintain its market share majority over Novo Nordisk in the booming market for weight loss and diabetes drugs. Some analysts estimate the segment could be worth about $100 billion by the 2030s.Retatrutide also met the trial’s other main goal of reducing pain from knee osteoarthritis – a common condition that wears down the joint’s cartilage and leads to pain and stiffness – by up to 62.6% on average when analyzing all patients, based on a widely used survey. More than 1 in 8 patients who took the drug were completely free from knee pain by the end of the trial, Eli Lilly said. One concern with current weight loss drugs is that they can lead to the loss of lean muscle mass. But Apovian said the results show that in adults with severe obesity, you can improve physical function with retatrutide. The results appear to surpass Wall Street’s expectations. In a note ahead of the findings, BMO Capital Markets analyst Evan Seigerman said his base-case assumption was for the drug to show weight loss of around 20% to 23%, with at least a 50% reduction in knee pain. The company believes retatrutide “could become an important option for patients with significant weight loss needs and certain complications, including knee osteoarthritis,” Kenneth Custer, president of Lilly Cardiometabolic Health, said in a statement. In a note Thursday, JPMorgan analyst Chris Schott said retatrutide’s tolerability data, or how well patients handle the treatment, is “somewhat worse vs Zepbound, though not surprising, in our view.” Roughly 18% of patients on the highest dose of the drug stopped treatment due to side effects, compared with 4% of those in the placebo group. Eli Lilly said those dropout rates were “highly correlated” to patients’ starting body mass index and included discontinuations due to “perceived excessive weight loss.” Among those with a BMI of 3 …
