SURMOUNT-ADOLESCENTS begins: the first tirzepatide weight trial in teenagers
Lilly's first tirzepatide trial in teenagers with obesity, called SURMOUNT-ADOLESCENTS, is testing weight loss in 160 kids ages 12 to 17, with results not expected before mid-2026.
Eli Lilly began a phase 3 trial in October 2023 testing tirzepatide, the drug sold as Zepbound and Mounjaro in adults, in teenagers with obesity for the first time. The study, registered as SURMOUNT-ADOLESCENTS, is enrolling 160 participants ages 12 to 17 who have obesity, or who are overweight and have at least one weight-related health condition [1].
The trial's main goal is to measure the percent change in body mass index, or BMI, at week 72 compared with a starting point [1]. Participants who complete that portion of the study can choose to continue into an optional extension period lasting up to 156 weeks, or roughly three years, allowing researchers to track longer-term effects [1].
This study is separate from Lilly's other pediatric research program for tirzepatide, which focused on type 2 diabetes in children and teens. That diabetes program led to a pediatric approval for Mounjaro in December 2025 [1]. SURMOUNT-ADOLESCENTS instead targets weight loss specifically, independent of whether a participant has diabetes.
The trial's primary completion date, the point when the main BMI measurement will be finished and the key data analyzed, is listed as June 2, 2026 [1]. As of September 14, 2026, no results from the trial had been published [1].
Why it matters for patients
Tirzepatide is already approved for adults through Zepbound for weight management and Mounjaro for type 2 diabetes. But approval in adults does not automatically extend to children and teenagers, whose bodies, growth patterns, and dosing needs can differ. A dedicated trial like SURMOUNT-ADOLESCENTS is a required step before regulators would consider approving tirzepatide specifically for weight loss in this younger age group [1].
For families of teenagers with obesity, this means that as of now, tirzepatide's use for weight management in that age group remains investigational rather than approved. The trial's design, requiring either an obesity diagnosis or overweight status plus a related health condition, mirrors how adult obesity trials for GLP-1 drugs have typically been structured, focusing on people who could benefit most from an intervention [1].
The optional 156-week extension also signals that researchers want data not just on short-term weight change but on what happens with continued use over several years, a question that matters for a population still growing and developing [1]. Until results are published, it is not yet known how effective or how well tolerated tirzepatide is in this age group, or what side effects might be more or less common in teenagers compared with adults.
What happens next
The trial's primary completion date is listed as June 2, 2026, which is when the main 72-week BMI outcome data should be finalized [1]. As of the most recent check on September 14, 2026, results had not yet been published [1]. Participants who choose the extension arm could remain in the study for up to three years beyond their initial 72-week period, meaning full long-term data may not be available for some time after the primary results are released [1]. Any regulatory review or potential approval for this specific use in adolescents would come only after that data is submitted to the Food and Drug Administration, a process not yet begun according to available information.
Sources
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