Semaglutide as adjunct treatment for obesity in adolescents receiving antipsychotic medication (the GOAL trial): protocol for a single-arm, open-label feasibility study.

introductionAdolescents treated with antipsychotic medication are at increased risk of obesity and metabolic complications, yet evidence-based interventions in this group remain limited. Glucagon-like peptide-1 receptor agonists have demonstrated efficacy in the treatment of obesity in both adults and adolescents. The aim of this trial is to assess the feasibility of a 36-week treatment period with a glucagon-like peptide-1 receptor agonist as an adjunct to standard care in adolescents with antipsychotic-associated obesity, defined as completion from baseline to end of treatment. The findings from this feasibility trial will inform the design and support the scale-up of a subsequent randomised controlled trial. METHODS AND ANALYSIS: The GOAL trial is a single-arm, open-label feasibility study conducted at Copenhagen University Hospital, Bispebjerg, Denmark, in collaboration with the Child and Adolescent Mental Health Center. A total of 34 adolescents aged 12-18 years with obesity, defined as body mass index SD score equal to or greater than +1.28 and body fat percentage at or above the 95th percentile, receiving stable antipsychotic treatment will be enrolled. The study population includes adolescents with a range of psychiatric diagnoses requiring antipsychotic treatment, including psychotic disorders, mood disorders and neurodevelopmental disorders. Adolescents receiving antipsychotic treatment under coercion are excluded. Participants will receive once-weekly subcutaneous semaglutide at a dose up to 2.4 milligrams for 36 weeks in addition to standard care, followed by an 18-month observational follow-up period. The primary outcome is study completion rate. Additional feasibility outcomes include recruitment rate, treatment adherence and completion of study procedures. Secondary outcomes include changes in body mass index SD score, body composition, metabolic biomarkers and psychiatric outcomes. Feasibility outcomes will be analysed descriptively. Exploratory longitudinal analyses will be conducted using linear mixed-effects models. ETHICS AND DISSEMINATION: The study complies with the Declaration of Helsinki and European Union Clinical Trials Regulation (536/2014) and is approved in the Clinical Trials Information System (2024-5 17 471-21-02). Written informed consent will be obtained from participants and their legal guardians. Results will be disseminated through peer-reviewed publications and scientific conferences. TRIAL REGISTRATION NUMBER: 2024-5 17 471-21-02.