Eli Lilly has already proven that its diabetes drug Mounjaro can help overweight and obese people lose weight, findings that could lead to a U.S. approval later this year.
New study results disclosed Thursday add to Mounjaro’s case, showing that the drug can help patients shed more pounds after diet or exercise has already helped, and that it must be used long-term for its benefits to hold up.
The trials, SURMOUNT-3 and SURMOUNT-4, may not be necessary for Lilly to gain Food and Drug Administration approval. But they could help guide physicians in treating overweight and obese people once Mounjaro, currently only marketed for diabetes, is cleared for use as a weight-loss treatment.
In Lilly’s first Phase 3 trial in obesity, SURMOUNT-1, Mounjaro was tested in obese people with underlying medical conditions and who were unable to lose weight despite lifestyle interventions. The drug, in that setting, helped patients lose up to 21% of their body weight after 72 weeks of treatment. In SURMOUNT-2, obese Type 2 diabetics treated with Mounjaro for 72 weeks lost up to 15% of their body weight.
The two trials reported on Thursday were designed to answer questions the others didn’t — whether people who successfully lose weight with diets and exercise can benefit from Mounjaro, and what happens when people stop taking Lilly’s drug.
After three months of a low-calorie diet, exercise and weekly counseling sessions, SURMOUNT-3 randomized 579 people who had already lost 5% of their body weight to take either Mounjaro or a placebo. The half taking Mounjaro lost an average of 21% of their body weight after 72 weeks, while those on a placebo gained 3%.
In SURMOUNT-4, all 783 enrollees were given Mounjaro for 36 weeks. Afterwards, 670 study participants were randomized to receive either Mounjaro or a placebo for another year. At the end of the trial’s initial phase, patients had lost, on average, 21% of their body weight. The group taken off Mounjaro subsequently regained 15% of their weight, while people who stayed on the drug lost roughly 7% more.
“The findings from SURMOUNT-3 challenge the notion that patients living with obesity or overweight can achieve their weight loss goals with diet and exercise alone,” said Jeff Emmick, Lilly’s senior vice president of product development, in a statement. “Additionally, the findings from SURMOUNT-4 reinforce that obesity should be regarded like other chronic diseases where chronic therapy may be needed to maintain treatment benefits."
The results “add continued evidence of [Mounjaro’s] value in achieving and maintaining weight loss,” wrote Leerink Partners analyst David Risinger, in a note to clients Thursday.
If approved in obesity, Mounjaro will face off against Novo Nordisk’s obesity drug Wegovy and diabetes medicine Ozempic, which contains the same active ingredient and is often used off-label for weight loss.
All three stimulate a hormone called GLP-1, which helps the body produce insulin. Mounjaro hits a second target called GIP as well.
Novo’s combined GLP-1 sales, which include some older drugs from the same class, amounted to $14.2 billion in 2022, and some estimate sales in the drug class could as high as $90 billion.
Lilly has another obesity project in its pipeline that in mid-stage testing looks at least as promising as Mounjaro. It also has an oral treatment in late-stage development.