OBJECTIVES: This study aimed to assess differences in insulin-like growth factor 1 (IGF-1) levels following the transition from somatropin to lonapegsomatropin in patients with pediatric growth hormone deficiency (GHD). Secondary objectives included the evaluation of dose titrations based on IGF-1 levels, changes in annualized height velocity (AHV) and body mass index (BMI), and assessing reported adverse effects associated with lonapegsomatropin therapy. METHODS: A single-center, retrospective review was conducted including patients diagnosed with pediatric GHD initially treated with somatropin who transitioned to lonapegsomatropin between January 1, 2022, and December 31, 2023. RESULTS: Fourteen patients (median age: 9 years) were included. The median somatropin dose was 0.18 mg/kg/week (range, 0.09 to 0.29) at the time of transition and patients were initiated on a median lonapegsomatropin dose of 0.23 mg/kg/week (range, 0.15 to 0.26). This resulted in an IGF-1 increase of 2.3 SDS post-switch. Dose adjustments were made based on IGF-1 levels. Five patients required immediate dose reductions
four of these required further adjustments due to persistent elevation. There were no serious adverse effects reported. CONCLUSIONS: Lonapegsomatropin may be a favorable option to reduce injection burden for those with pediatric GHD, though the manufacturer's recommended starting dose of 0.24 mg/kg/week may require individualization. Careful monitoring and dose adjustment based on IGF-1 levels are necessary to maintain safety and efficacy.