Semaglutide, A Long-Acting GLP-1 Analogue, for the Management of Early Onset Obesity due to MC4R defect – A Case Report

Introduction: Childhood obesity is a global concern and has both nutritional and genetic causative factors. One of the most common monogenic causes of obesity is heterozygous mutations in the Melanocortin 4 receptor (MC4R), which are found in 5.7% to 8.6% of individuals with early-onset obesity. We report, the effect of Semaglutide, a long-acting Glucagon like peptide (GLP1) analogue, in the treatment of severe obesity in an adolescent boy with a heterozygous mutation in MC4R. Case presentation: A 13-year-old boy with a history of excessive weight gain since infancy was referred to the specialised weight management team. He was born at full-term with a birth weight of 3.57kg (50th centile), but his weight consistently exceeded the 99.6th percentile after the age of one year. At the age of five years, he was diagnosed with autism spectrum disorder (ASD). Diagnostic investigations revealed insulin resistance, and dyslipidaemia, while genetic testing confirmed a heterozygous mutation in MC4R (E61K), inherited from his mother. Managing his condition was challenging due to his rapid weight gain, needle phobia, and behavioural difficulties. Despite intense multidisciplinary lifestyle interventions, he continued to gain weight, reaching a peak weight of 187.5kg [+16.65 standard deviation score (SDS)], body mass index (BMI) of 56.9kg/m2 (+4.19 SDS), body fat 63.9%] at the age of 13 years. Due to severe ASD and needle phobia, he was not keen on daily GLP-1 injections. He was commenced on Semaglutide subcutaneous injection at a dose of 0.25mg weekly, gradually increasing to the maximum dose of 1mg weekly. Over the course of 12 weeks, his BMI decreased to 52.2kg/m2 (+4.08SDS) and weight dropped to 176.8kg (+14.76SDS, body fat: 52.7%). At the 3-month and 12-month reviews post treatment, he achieved weight loss of 5.7% and 11% respectively. Quality of life questionnaire (QoL) showed improved scores from 35.95 to 60.36 at 12-month review indicating enhanced well-being. The CGM (continuous glucose monitor) demonstrated an improvement in TIR (time in range). Conclusion: Semaglutide, is approved by the FDA for weight management in adolescents aged 12 years and above in December 2022. A recent case series underscored the benefits of therapy with Liraglutide, a short-acting GLP-1 analogue, in rare genetic cases of early-onset obesity. To our knowledge, this is the first case report to highlight the efficacy and safety of Semaglutide in an adolescent with heterozygous MC4R mutation. Semaglutide could be a potential treatment option for monogenic obesity and will benefit from further research.