TLDR
- Eli Lilly’s investigational drug retatrutide helped patients lose up to 70.3 pounds (28.3% of body weight) over 80 weeks in a Phase 3 trial.
- Results appear stronger than Lilly’s current weight-loss drugs Zepbound and Foundayo across different trials.
- Around 45% of the 2,500 trial participants achieved 30% or more weight loss — a level previously only associated with bariatric surgery.
- A lower 4mg dose showed a strong tolerability profile, with fewer discontinuations than even the placebo group.
- LLY stock rose around 1% Thursday morning; the stock is still down about 5% year-to-date.
Eli Lilly’s next weight-loss drug just posted some of the most eye-catching numbers seen in obesity medicine.
Retatrutide, a weekly injection that targets three gut hormones, cleared a critical late-stage trial Thursday. Patients with obesity taking the highest 12mg dose lost an average of 28.3% of their body weight — roughly 70.3 pounds — over 80 weeks. Those on the 9mg dose lost 64.4 pounds on average.
The placebo group, by contrast, lost just 2.2% of their body weight.
LLY stock was up around 1% in morning trading Thursday. The stock is still down about 5.2% year-to-date as competition in the GLP-1 market intensifies.
About 45% of the roughly 2,500 patients in the Phase 3 trial hit 30% or more total weight loss. That threshold has historically only been reached through bariatric surgery.
Dan Skovronsky, Lilly’s chief scientific and product officer, told CNBC that 30% weight loss is “an incredible number to see” with this class of medicine.
How Retatrutide Compares to Existing Drugs
Retatrutide works differently from Lilly’s current lineup. It activates receptors for three hormones — GLP-1, GIP, and glucagon — compared to two for Zepbound and one for older GLP-1 drugs.
While direct comparisons across different trials are tricky, the numbers stand out. Zepbound’s highest dose produced around 20–22% weight loss in its pivotal trial. Foundayo, Lilly’s oral GLP-1 pill, came in lower still.
A new 4mg dose tested in this trial also surprised analysts. It produced 19% weight loss — similar to Zepbound at high doses — but with a better tolerability profile. Just 4% of patients on that dose stopped treatment due to side effects, compared to nearly 5% in the placebo group.
The drug’s safety profile was broadly in line with other GLP-1 medications. Gastrointestinal side effects like nausea (42% at the highest dose) and diarrhea (32%) were the most common. No cardiac or liver issues were observed, which some analysts had flagged as a potential concern given the drug’s glucagon component.
Lilly said a slightly higher rate of urinary tract infections was seen versus placebo, though most were mild. Skovronsky suggested the UTIs may be linked to the speed and degree of weight loss, noting a similar pattern has been seen after bariatric surgery.
What Comes Next for Retatrutide
This is the third positive late-stage result for retatrutide. It previously succeeded in a diabetes trial earlier this year and cleared a smaller study on patients with obesity and knee arthritis in December 2025.
TD Cowen analysts have estimated the drug could generate $3.8 billion in sales by 2030, assuming approval.
Lilly holds around 60% of the GLP-1 market, per its own figures. Novo Nordisk’s Wegovy pill has gained ground in the oral weight-loss segment, where Lilly’s Foundayo also competes.
Lilly said it plans to use these results to move toward a regulatory filing for retatrutide.
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