A new experimental weight loss drug from Eli Lilly has helped people shed up to 30 percent of their body weight, or roughly 85 pounds, in a late stage clinical trial. The results, announced by the company, rival the effects of bariatric surgery, which typically produces 25 to 35 percent weight loss within one to two years. One expert called the findings the largest weight loss ever seen in any medication trial.
The drug, called retatrutide, belongs to the same class of medications as popular treatments like Wegovy and Zepbound, which mimic a hormone known as GLP-1. But retatrutide is a so called triple agonist. It also mimics two additional hormones: GIP and glucagon. In the phase 3 trial of about 2,300 patients with obesity or who were overweight, participants taking the highest weekly dose lost an average of 28 percent of their body weight, or about 70 pounds. Nearly half of those patients lost 30 percent or more. A smaller group with severe obesity continued the drug for up to 104 weeks and lost an average of 85 pounds.
By comparison, patients in earlier trials of Zepbound lost about 21 percent of their body weight over 72 weeks, and those on Wegovy lost around 15 percent after 68 weeks. Experts caution these are not direct head to head comparisons. Still, doctors say retatrutide could be a game changer, especially for patients with severe obesity who may not lose enough weight on current GLP-1 drugs. “Bariatric surgery can provide that, but it seems like retatrutide is also going to be an effective tool to help patients with a higher BMI achieve a healthy weight,” said Dr. Shauna Levy, medical director of the Tulane Weight Loss Center.
Side effects were similar to those seen with other GLP-1 drugs and included nausea, constipation and diarrhea. Patients also reported more unusual skin sensations and urinary tract infections compared with the placebo group. The dropout rate was higher than for Zepbound but similar to Wegovy. Eli Lilly has not yet filed for Food and Drug Administration approval but expects to do so as early as this year.
If approved, retatrutide could offer new hope for the roughly 10 percent of patients who do not respond to current GLP-1 medications. “This could be very useful for patients who are GLP-1 non-responders,” said Dr. Susan Spratt, an endocrinologist at Duke Health. As the next generation of weight loss drugs moves closer to market, the outlook for patients struggling with obesity continues to brighten.