Eli Lilly’s highly anticipated GLP-1 drug retatrutide helped people with type 2 diabetes lose up to 60 pounds, or about 23 percent of their body weight, according to late-stage trial results published Tuesday in The Lancet.
This is the largest weight loss ever recorded in a drug trial for diabetic patients, a group that often has more difficulty losing weight.
In clinical trials of semaglutide and tirzepatide, people with type 2 diabetes lost up to 10% (21 pounds) and 15% (34 pounds), respectively, of their body weight. (These are not direct comparisons because the drugs have not been evaluated in comparative clinical trials.)
Retatrutide “is truly a breakthrough in diabetes care,” said Dr. Susan Spratt, an endocrinologist and senior medical director of the Office of Population Health Management at Duke Health in North Carolina. She did not participate in the lawsuit and does not receive money from Eli Lilly. “It rivals non-surgical gastric bypass.”
Spratt said many diabetes medications, such as insulin, cause weight gain.
“It can be daunting to successfully manage your diabetes while gaining weight,” she said.
Lilly’s trial included more than 1,110 patients who had an average starting weight of about 234 pounds and an average body mass index, or BMI, of about 38. People were randomly assigned to take one of three weekly doses of retatrutide or a placebo for 80 weeks. By the end of the trial, the BMI of more than half of the participants had fallen below 30, the threshold for obesity.
Results of another trial, published Tuesday in the New England Journal of Medicine, found that retatrutide helped patients without type 2 diabetes who were obese or overweight lose up to 70 pounds, or 25% of their body weight on average, after 80 weeks. This data included a subset of patients with severe obesity, who lost up to 85 pounds, or 30% of their body weight, after 104 weeks – the largest weight loss ever recorded in a drug trial and comparable to bariatric surgery.
Like semaglutide and tirzepatide, retatrutide works by mimicking a hormone called GLP-1. What sets retatrutide apart is its classification as a “triple agonist.” Lilly’s tirzepatide, a “dual agonist,” mimics two hormones (GLP-1 and GIP), and retatrutide targets three by adding a hormone called glucagon.
Lilly has not submitted retatrutide for approval to the Food and Drug Administration, but its clinical trial results have already made it one of the pharmaceutical industry’s most anticipated treatments. Lilly says it plans to file for approval early next year.
Unauthorized and copied versions of retatrutide are already being manufactured and sold through wellness platforms, medical spas, and compounding pharmacies. The drug is often labeled as “for research use only”, a legal solution to selling compounds they say are not intended for humans. Lilly has filed lawsuits against companies selling unapproved versions of the drug.
Other benefits of Retatrutide
Retatrutide also helps reduce the severity of sleep apnea and lower knee arthritic pain. Previous data suggests the drug appears to help the heart.
The new trial found that retatrutide, like other GLP-1 drugs originally developed as diabetes medications, effectively lowered blood sugar levels in diabetic patients.
Retatrutide lowered A1C levels – a measure of a person’s average blood sugar level over the previous two to three months – by up to 1.6%, compared to 0.2% with a placebo, according to trial results.
Up to 40% of patients in the trial achieved an HbA1c level below 5.7%, below the threshold for diabetes and prediabetes.
“The data on retatrutide are very interesting,” Dr. Michelle Ponder, an assistant professor of medicine at Duke University School of Medicine in North Carolina, wrote in an email. An A1C level of 5.7% means “their diabetes has gone into remission,” said Ponder, who was not involved in Lilly’s trial.
She added, however, that retatrutide “may be too strong for some patients,” particularly those with mild diabetes or slightly elevated weight.
They “might be better suited to drugs already on the market, like Ozempic or Mounjaro,” she said.
She added that with each change in medication, patients may experience a change in the frequency of side effects.
Side effects of retatrutide were similar to other GLP-1 drugs, with patients most commonly reporting diarrhea, nausea, constipation, and vomiting. Lilly said the side effects were mild to moderate in severity. About 8% of people in the trial taking the highest dose stopped taking the drug, compared with about 5% of people taking the placebo.
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