Lilly’s Tirzepatide Shows Strong Weight Loss Efficacy in Phase III Study

Eli Lilly_iStock, jetcityimage

Pictured: Eli Lilly's office in Indianapolis/iStock, jetcityimage

Full results from the Phase III SURMOUNT-3 trial showed that Eli Lilly’s tirzepatide induces strong and long-lasting weight loss when given after an intensive lifestyle intervention program, the company announced Sunday.

SURMOUNT-3, a randomized, double-blinded, placebo-controlled and parallel trial, enrolled 806 overweight or obese adults who had weight-related comorbidities, excluding type 2 diabetes. All participants underwent a 12-week intensive lifestyle adjustment program, after which those who lost at least 5% of their body weight continued on to receive tirzepatide or placebo.

At the 72-week follow-up, participants in the tirzepatide group saw a 21.1% mean weight loss, whereas placebo counterparts gained 3.3% bodyweight on average. Over the entire 84-week study period— including the 12-week lifestyle intervention lead-in—tirzepatide-treated participants achieved a 26.6% total mean weight loss, as opposed to only 3.8% in the placebo arm.

The results were published Sunday in the journal Nature Medicine and were presented by Lilly over the weekend during The Obesity Society’s ObesityWeek 2023, held in Dallas, Texas.

“While intensive lifestyle intervention is an important part of obesity management, these results underscore the difficulty some people face maintaining weight loss with diet and exercise alone,” Jeff Emmick, senior vice president of product development at Lilly, said in a statement. Adding tirzepatide to an intensive lifestyle regimen could lead to “greater, longer-lasting weight reduction,” he added.

Tirzepatide’s safety profile in SURMOUNT-3 was consistent with what had previously been reported. The most common side effects were gastrointestinal toxicities, such as nausea, diarrhea and constipation, which were generally mild to moderate in severity.

Around 10% of patients taking tirzepatide dropped out of the study due to adverse events, while only 2.1% of placebo comparators did so.

Tirzepatide is a peptide therapeutic that works by targeting and activating both the GIP and GLP-1 receptors, which are found in the area of the brain responsible for appetite regulation. It won the FDA’s approval in May 2022 for the treatment of type 2 diabetes, for which tirzepatide is being marketed under the brand name Mounjaro.

Lilly is also developing tirzepatide as a weight-loss treatment, for which the company’s rolling submission to the FDA is currently ongoing, according to its website. In October 2022, the FDA granted tirzepatide its Fast Track designation in this indication.

Joining tirzepatide in Lilly’s weight-loss arsenal is orforglipron, an investigational oral non-peptide agonist of the GLP-1 receptor. In June 2023, the company posted mid-stage data demonstrating that the candidate can cut 8.6% to 12.6% of participants’ body weight after 26 weeks.

In July 2023, Lilly dropped $1.93 billion to acquire Versanis and its weight-loss monoclonal antibody bimagrumab.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. He can be reached at or

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