STEP Young phase 3 trial shows greater BMI reduction with semaglutide in children aged 6 to under 12, with 40.4% moving below the obesity threshold.
Written By: Anamika Koshti, PharmD
Reviewed By: Pharmacally Editorial Team
Novo Nordisk has reported first results from the phase 3 STEP Young trial (NCT05726227) evaluating once-weekly subcutaneous semaglutide in children aged 6 to under 12 years with obesity. The randomized, double-blind, placebo-controlled, multinational trial met its primary endpoint, demonstrating greater reduction in body mass index (BMI) at week 68 with semaglutide than with placebo. Both treatment groups received lifestyle modification consisting of a reduced-calorie diet and increased physical activity throughout the trial.
Trial Population and Treatment Approach
STEP Young enrolled 165 children aged 6 to under 12 years with obesity. Participants received once-weekly subcutaneous semaglutide or placebo alongside lifestyle modification. The maximum semaglutide dose was either 1.7 mg or 2.4 mg, determined according to the child’s weight at the start of the trial.
The study population had a high degree of obesity severity. More than 85% of enrolled children had class II or class III severe obesity at baseline, defined using pediatric BMI criteria corresponding to BMI at least 120% or 140%, respectively, of the 95th percentile for age and sex.
Because BMI changes with age and growth during childhood, BMI classification in STEP Young was based on CDC sex- and age-specific BMI growth charts. Obesity was defined as BMI at or above the 95th percentile for age and sex.
BMI Reduction and Change in Obesity Classification
The primary endpoint was change in BMI from baseline at week 68. The trial demonstrated superior BMI reduction with semaglutide compared with placebo. The confirmatory secondary endpoint assessed improvement in BMI classification over the same period.
At week 68, 40.4% of children treated with semaglutide were no longer classified as having obesity, compared with 0% of those receiving placebo. Thus, approximately two out of five children in the semaglutide group moved below the pediatric obesity threshold, into either the normal-weight or overweight BMI classification.
The 40.4% finding is reported using the trial product estimand, representing the treatment effect if all children adhered to treatment. This distinction is important when interpreting the topline efficacy result.
The supportive secondary endpoints included changes in anthropometric measures, cardiovascular risk factors, glucose metabolism and body composition in a DXA subgroup. Assessments extend to week 104.
Safety and Developmental Assessments
The overall safety and tolerability profile of semaglutide in STEP Young was consistent with previous Novo Nordisk pediatric and adult trials involving semaglutide and liraglutide. No new safety concerns were identified. The company also reported no safety concerns related to growth or pubertal development.
The growth and pubertal-development findings are particularly relevant when evaluating pharmacological treatment in younger children, given that participants remain in an active period of physical development. The available topline results therefore provide an initial safety assessment alongside the observed BMI response, while the full dataset will be needed to characterize the efficacy and safety profile in greater detail.
Clinical Perspective
The STEP Young findings extend clinical investigation of semaglutide into a younger pediatric population with obesity, including children with substantial baseline obesity severity. The combination of BMI reduction and movement below the age- and sex-specific obesity threshold provides two clinically relevant measures of response from the trial.
However, the currently available findings are topline results. Detailed efficacy, safety and supportive endpoint data have not yet been presented. Full STEP Young results are scheduled for presentation at ObesityWeek 2026, November 14-17, in Washington, DC.
Semaglutide is a GLP-1 receptor agonist that mimics the effects of naturally occurring GLP-1, which has roles in regulation of blood glucose and body weight. Its evaluation in STEP Young represents an extension of its clinical development in obesity to children aged 6 to under 12 years.
Reference
Novo Nordisk A/S. Novo Nordisk STEP Young phase 3 data: 40.4% of children living with obesity achieved a BMI below the obesity threshold with semaglutide and lifestyle modification. September 7, 2026.
About the Writer
Anamika Koshti (LinkedIn) is a PharmD professional and healthcare writer with interests in clinical research, pharmacovigilance, and evidence-based medicine. She has authored peer-reviewed publications on Alzheimer’s disease and PCOS, presented research at national conferences, and gained hands-on experience in medical content development and clinical data interpretation. She is committed to translating complex medical research into accurate, accessible content for healthcare professionals and patients.