SURMOUNT-1: Tirzepatide results in 22.5% weight loss in adults with obesity or overweight

Updated: Jun 8

Tirzepatide (5 mg, 10 mg, 15 mg) achieved superior weight loss compared to placebo at 72 weeks of treatment in topline results from Eli Lilly and Company's SURMOUNT-1 clinical trial, with participants losing up to 22.5% (52 lb. or 24 kg) of their body weight for the efficacy estimandi.

This study enrolled 2,539 participants and was the first phase 3 global registration trial evaluating the efficacy and safety of tirzepatide in adults with obesity, or overweight with at least one comorbidity, who do not have diabetes.

Tirzepatide met both co-primary endpoints of superior mean percent change in body weight from baseline and greater percentage of participants achieving body weight reductions of at least 5% compared to placebo for both estimandsii. The study also achieved all key secondary endpoints at 72 weeks.


For the efficacy estimand, participants taking tirzepatide achieved average weight reductions of 16.0% (35 lb. or 16 kg on 5 mg), 21.4% (49 lb. or 22 kg on 10 mg) and 22.5% (52 lb. or 24 kg on 15 mg), compared to placebo (2.4%, 5 lb. or 2 kg). Additionally, 89% (5 mg) and 96% (10 mg and 15 mg) of people taking tirzepatide achieved at least 5% body weight reductions compared to 28% of those taking placebo.


In a key secondary endpoint, 55% (10 mg) and 63% (15 mg) of people taking tirzepatide achieved at least 20% body weight reductions compared to 1.3% of those taking placebo. In an additional secondary endpoint not controlled for type 1 error, 32% of participants taking tirzepatide 5 mg achieved at least 20% body weight reductions. The mean baseline body weight of participants was 231 lb. (105 kg).

"Obesity is a chronic disease that often does not receive the same standard of care as other conditions, despite its impact on physical, psychological and metabolic health, which can include increased risk of hypertension, heart disease, cancer and decreased survival," said Dr Louis J Aronne, director of the Comprehensive Weight Control Center and the Sanford I Weill Professor of Metabolic Research at Weill Cornell Medicine, obesity expert at NewYork-Presbyterian/Weill Cornell Medical Center and Investigator of SURMOUNT-1. "Tirzepatide delivered impressive body weight reductions in SURMOUNT-1, which could represent an important step forward for helping the patient and physician partnership treat this complex disease."


Tirzepatide is a novel investigational once-weekly GIP (glucose-dependent insulinotropic polypeptide) receptor and GLP-1 (glucagon-like peptide-1) receptor agonist, representing a new class of medicines being studied for the treatment of obesity. Tirzepatide is a single peptide that activates the body's receptors for GIP and GLP-1, two natural incretin hormones. Obesity is a chronic, progressive disease caused by disruptions in the mechanisms that control body weight, often leading to an increase in food intake and/or a decrease in energy expenditure. These disruptions are multifactorial and can be related to genetic, developmental, behavioural, environmental and social factors.


For the treatment-regimen estimandiii, results showed:

  • Average body weight reductions: 15.0% (5 mg), 19.5% (10 mg), 20.9% (15 mg), 3.1% (placebo)

  • Percentage of participants achieving body weight reductions of ≥5%: 85% (5 mg), 89% (10 mg), 91% (15 mg), 35% (placebo)

  • Percentage of participants achieving body weight reductions of ≥20%: 30% (5 mg, not controlled for type 1 error), 50% (10 mg), 57% (15 mg), 3.1% (placebo)

The overall safety and tolerability profile of tirzepatide was similar to other incretin-based therapies approved for the treatment of obesity. The most commonly reported adverse events were gastrointestinal-related and generally mild to moderate in severity, usually occurring during the dose escalation period. For those treated with tirzepatide (5 mg, 10 mg and 15 mg, respectively), nausea (24.6%, 33.3%, 31.0%), diarrhoea (18.7%, 21.2%, 23.0%), vomiting (8.3%, 10.7%, 12.2%) and constipation (16.8%, 17.1%, 11.7%) were more frequently experienced compared to placebo (9.5% [nausea], 7.3% [diarrhoea], 1.7% [vomiting], 5.8% [constipation]).


Treatment discontinuation rates due to adverse events were 4.3% (5 mg), 7.1% (10 mg), 6.2% (15 mg) and 2.6% (placebo). The overall treatment discontinuation rates were 14.3% (5 mg), 16.4% (10 mg), 15.1% (15 mg) and 26.4% (placebo).


Participants who had pre-diabetes at study commencement will remain enrolled in SURMOUNT-1 for an additional 104 weeks of treatment following the initial 72-week completion date to evaluate the impact on body weight and the potential differences in progression to type 2 diabetes at three years of treatment with tirzepatide compared to placebo.


"Tirzepatide is the first investigational medicine to deliver more than 20 percent weight loss on average in a phase 3 study, reinforcing our confidence in its potential to help people living with obesity," said Dr Jeff Emmick, vice president, product development, Lilly. "Obesity is a chronic disease that requires effective treatment options, and Lilly is working relentlessly to support people with obesity and modernize how this disease is approached. We're proud to research and develop potentially innovative treatments like tirzepatide, which helped nearly two thirds of participants on the highest dose reduce their body weight by at least 20 percent in SURMOUNT-1."