Eli Lilly Announces Retatrutide Weight Loss Results Retatrutide, 28.3%
Eli Lilly announced weight loss results retatrutide showed up to 28.3% average weight loss over 80 weeks in a phase three trial of 2,339 adults with obesity or overweight and no diabetes. The 12mg dose produced the largest reduction, averaging 70.3lb.
That result came with side effects that rose with dose. Nausea affected 42.4% of participants on 12mg, compared with 14.8% on placebo, and diarrhea was reported by 32.0% on 12mg versus 13.5% on placebo.
Retatrutide and Duke Health
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” and, “This is huge.”
Retatrutide is a once-weekly triple hormone receptor agonist that acts as a GLP-1, like Wegovy and Zepbound, and a GIP, like Zepbound, while also including glucagon. Eli Lilly said the drug helped participants lose more weight than other obesity drugs already on the market.
12mg Dose Results
Participants receiving the 12mg dose lost 25.3 percentage points more body weight than the 4mg group, which averaged 19.0% loss and 47.2lb over 80 weeks. The 9mg group averaged 25.9% loss and 64.4lb.
Eli Lilly said 45.3% of participants on 12mg achieved at least 30% weight loss. The company also said 65.3% of participants on the 12mg regimen reduced their BMI below 30, and 37.5% of those who began the trial with a BMI of 40 or higher reached that level.
Wegovy and Zepbound
The company’s comparison point is existing treatment expectations: Zepbound users can expect to lose an average of 15% to 20% of starting body weight over 72 weeks, while Wegovy users can expect to lose an average of 14% to 19% over 64 to 72 weeks. The retatrutide trial also reported constipation in roughly one-quarter of treated patients, vomiting in up to one in four patients on the highest dose, and upper respiratory tract infections in 13.1% on 12mg.
For patients and doctors looking at the data now, the 12mg results set the benchmark inside this trial: the strongest weight loss came with the highest side-effect rates. Lilly’s next step is the larger question left by the phase three readout — whether the dose that produced the biggest reductions can also support use in routine treatment.
