Experimental weight loss drug retatrutide shows dramatic weight loss in clinical trial

Amid the growing demand for GLP-1 medications for weight loss, a new experimental drug, retatrutide, stands out, according to new clinical trial results released on Thursday.

The drug led to an average weight loss of 70.3 pounds over 80 weeks in patients with obesity, with 45% of patients on 12 mg of the once-weekly injectable retatrutide losing up to 30% of their body weight, the drugmaker, Eli Lilly and Company, said in a news release.

Those results are comparable to what is seen with bariatric surgery, according to Eli Lilly, which also makes the weight loss drug Zepbound.

Unlike current blockbuster medications such as Ozempic, Wegovy, Mounjaro and Zepbound, retatrutide targets three hormone receptors -- GIP, GLP-1 and glucagon -- earning it the nickname of a "triple agonist" drug.

Researchers believe the glucagon-targeting effect may help the body burn additional energy while also reducing appetite and improving blood sugar control.

For comparison, a major clinical trial published in the New England Journal of Medicine found adults taking semaglutide -- the active ingredient in Wegovy -- lost an average of 14.9% of their body weight over 68 weeks.

Meanwhile, a separate clinical trial, also published in the New England Journal of Medicine, found participants taking tirzepatide -- the active ingredient in Zepbound -- lost up to 22.5% of their body weight over 72 weeks.

Retatrutide remains experimental and has not yet been approved by the U.S Food and Drug Administration.

The company expects to potentially seek FDA approval sometime in late 2027 or early 2028.

The results of the clinical trial released Thursday have not yet been published in a peer-reviewed medical journal, nor have they undergone peer review.

Like other weight loss drugs, retatrutide also comes with reported side effects, the most common being gastrointestinal symptoms including nausea, diarrhea and vomiting, according to Eli Lilly. Some patients also reported moderate-to-mild urinary tract infection or skin discomfort.

The company said that in its most recent clinical trial, the discontinuation rate due to side effects increased with the dosage, with the highest discontinuation rate, 11.3%, at the highest dosage of 12 mg.

Medical professionals caution that clinical trials are not complete and the safety and effectiveness will be evaluated by the FDA before any form of retatrutide is available outside of clinical trials.

Anyone buying or selling retatrutide at this time is not dealing with authentic medication and the contents and dosage would be unknown and potentially very dangerous.

Editor’s note: This report has been updated to reflect findings from the TRIUMPH-1 clinical trial released on May 21, 2026 by Eli Lilly and Company.