Abstract Context Somapacitan is a long-acting GH derivative for treatment of GH deficiency (GHD). Objective Evaluate the efficacy and tolerability of somapacitan in children with GHD after 2 years of treatment and after the switch from daily GH. Design A randomized, multinational, open-labelled, controlled parallel group phase 3 trial, comprising a 52-week main phase and 3-year safety extension (NCT03811535). Setting Eighty-five sites across 20 countries. Patients A total of 200 treatment-naïve prepubertal patients were randomized and exposed; 194 completed the 2-year period. Interventions Patients were randomized 2:1 to somapacitan (0.16 mg/kg/wk) or daily GH (0.034 mg/kg/d) during the first year, after which all patients received somapacitan 0.16 mg/kg/wk. Main outcome measures Height velocity (HV; cm/year) at week 104. Additional assessments included HV SD score (SDS), height SDS, IGF-I SDS, and observer-reported outcomes. Results HV was sustained in both groups between 52 and 104 weeks. At week 104, mean (SD) for HV between weeks 52 and 104 was 8.4 (1.5) cm/year after continuous somapacitan treatment and 8.7 (1.8) cm/year after 1 year of somapacitan treatment following switch from daily GH. Secondary height-related endpoints also supported sustained growth. Mean IGF-I SDS during year 2 was similar between groups and within normal range (−2 to +2). Somapacitan was well tolerated, with no safety or tolerability issues identified. GH patient preference questionnaire results show that most patients and their caregivers (90%) who switched treatment at year 2 preferred once-weekly somapacitan over daily GH treatment. Conclusions Somapacitan in children with GHD showed sustained efficacy and tolerability for 2 years, and after switching from daily GH. Patients/caregivers switching from daily GH expressed a preference for somapacitan. Clinical Trial Registration NCT03811535