STEP TEENS: semaglutide in adolescents aged 12 to 17

Why this study matters

Weekly semaglutide (Wegovy, Ozempic) 2.4 mg was already used to treat obesity in adults, but there had been no large trial in teenagers. Obesity in adolescence often continues into adulthood and brings weight-related health conditions early. STEP TEENS is the main randomized evidence on this medicine in people aged 12 to 17. Canadian parents and teens may hear about it when discussing treatment options with a clinician.

Who was in the study

The trial enrolled 201 adolescents aged 12 to under 18. To join, a teen needed obesity (a BMI at or above the 95th percentile for their age and sex) or overweight (a BMI at or above the 85th percentile) with at least one weight-related health condition. In practice, all but one participant had obesity. BMI (body mass index) compares weight with height; in children and teens it is judged against growth charts rather than a single cut-off.

Of the 201 who were randomized, 180 (90%) completed treatment. The trial ran for 68 weeks. The summary we reviewed does not say which countries took part.

What the researchers did

This was a double-blind, randomized, placebo-controlled trial. Randomized means chance decided who got which treatment. Double-blind means neither the teens nor the study staff knew who was on the medicine. Placebo means an inactive injection that looked the same.

Participants were assigned in a 2:1 ratio to semaglutide 2.4 mg injected once a week, or to placebo, for 68 weeks. Everyone also received a lifestyle intervention, meaning support with food and physical activity.

The main outcome was the percentage change in BMI from the start to week 68. This is different from adult trials, which usually measure percentage change in body weight. The confirmatory secondary outcome was losing at least 5% of starting body weight at week 68. The analysis counted everyone who was randomized, whether or not they stayed on the medicine or used other treatments. This is called a treatment-policy estimand, meaning the question was "what happens to teens assigned to this treatment".

What they found

Mean BMI changed by -16.1% with semaglutide and +0.6% with placebo (R32-C13). The estimated difference was -16.7 percentage points, with a 95% confidence interval of -20.3 to -13.2. A confidence interval is the range where the true difference most likely lies.

The odds ratio for losing at least 5% of body weight was 14.0 (95% CI 6.3 to 31.0), meaning this outcome was far more likely with semaglutide. Reductions in body weight and improvements in waist size, HbA1c (a measure of average blood sugar over about three months), blood fats (except HDL cholesterol) and a liver enzyme called ALT were also greater with semaglutide.

Side effects and people who stopped

Stomach and gut side effects occurred in 62% of the semaglutide group and 42% of the placebo group. Gallstones (cholelithiasis) were reported in 5 teens (4%) on semaglutide and none on placebo (R32-C14). Serious adverse events were reported in 15 of 133 (11%) on semaglutide and 6 of 67 (9%) on placebo. The summary we reviewed does not report how many teens stopped treatment because of side effects.

What this study does not tell you

• The main result is BMI change, not the percentage body-weight change used in adult trials, so the numbers cannot be compared directly with adult results.
• With 201 participants, the trial was too small to detect rare harms.
• It ran for 68 weeks. It does not say what happens to growth, weight or health over many years, or what happens after stopping.
• Both groups had lifestyle support, so the result shows what the medicine added on top of that support.
• The trial did not measure effects on eating behaviour or mental health in detail.
• The trial was funded by the maker of semaglutide.

What it means in Canada

STEP TEENS is the key trial behind the use of weekly semaglutide 2.4 mg in adolescents. Decisions about a teenager's treatment involve growth, family context and long-term follow-up, which this page does not cover. For how the medicine is used in Canada, see semaglutide in Canada. For funding questions, see public drug coverage by province.

Related reading

Other studies in this library that bear on the same question.

Source