Eli Lilly reports 28.3% weight loss in Anti-obesity Medication trial

Eli Lilly said its anti-obesity medication retatrutide produced up to 28.3% average weight loss in a phase three trial, with the highest-dose group losing 70.3lbs over 80 weeks. The trial also tracked side effects that were more common at higher doses, including nausea, diarrhea and vomiting.

Retatrutide at 12mg

The trial included 2,339 adults who had obesity or were overweight, had at least one weight-related comorbidity and had no diabetes. Participants were randomized to receive retatrutide in 4mg, 9mg or 12mg doses, or a placebo.

On the 12mg dose, 45.3% of participants lost at least 30% of their body weight. Eli Lilly also said 65.3% of people on that regimen reduced their BMI below 30, and 37.5% of those who started with a BMI of 40 or higher moved below that threshold.

Susan Spratt on the trial

Susan Spratt, an endocrinologist and senior medical director for the Population Health Management Office at Duke Health in North Carolina, said, “This is the largest weight loss I’ve ever seen in any medication trial.” She added, “This is huge.”

Her reaction tracks with the numbers from the study: participants on the 9mg dose lost an average of 64.4lbs, or 25.9%, and those on 4mg lost 47.2lbs, or 19.0%.

Zepbound and Wegovy

Eli Lilly said retatrutide appears to exceed what has typically been possible with other weight-loss medications on the market, including Zepbound and Wegovy. The company said Zepbound users can expect average weight loss of 15% to 20% over 72 weeks, while Wegovy users can expect 14% to 19% over 64 to 72 weeks.

Retatrutide and Zepbound are both injected once a week with the dose increasing incrementally over time. Retatrutide also includes glucagon, a hormone that none of the other weight-loss drugs on the market have.

Side effects in Lilly study

Nausea was reported in 28.6% of participants on 4mg, 38.4% on 9mg and 42.4% on 12mg, compared with 14.8% in the placebo group. Diarrhea affected 25.2% of patients on 4mg, 34.1% on 9mg and 32.0% on 12mg, versus 13.5% on placebo.

Constipation was reported by roughly one-quarter of treated patients, compared with 10.9% of those receiving placebo. Vomiting occurred in up to one in four patients on the highest dose, compared with 4.8% in the placebo group, and upper respiratory tract infections were reported in 14.2% on 4mg, 12.2% on 9mg and 13.1% on 12mg, versus 11.6% on placebo.