Once-Weekly Somapacitan Versus Daily Growth Hormone in Growth Hormone Deficiency: 2-Year Efficacy Results From REAL 3, a Randomized Phase 2 Trial
Authors: Sävendahl Lars S , Battelino Tadej , Rasmussen Michael Højby , Horikawa Reiko , Saenger Paul 
Published: May 2021

Abstract
Current treatment for growth hormone (GH) deficiency (GHD) requires daily injections, which can be burdensome for the patients/caregivers. Once-weekly somapacitan is a long-acting GH derivative currently in phase 3 for use in children with GHD and phase 2 for short children born small for gestational age. A phase 2, multinational, randomized, open-label, controlled trial (NCT02616562) investigated the efficacy and safety of somapacitan in children compared with daily GH (Norditropin®). GH-treatment-naïve prepubertal children with GHD received 0.04 (n=16), 0.08 (n=15) or 0.16 mg/kg/week (n=14) subcutaneous (s.c.) somapacitan, or s.c. daily GH 0.034 mg/kg/day (0.24 mg/kg/week; n=14) for 52 weeks, followed by a 104-week safety extension. In the extension phase, all patients on somapacitan received 0.16 mg/kg/week; daily GH dose remained unaltered. The 52-week efficacy and safety results have been reported previously. We report here the efficacy results after 104 weeks of GH treatment. At week 104, mean (standard deviation [SD]) height velocity (HV) in the first year of the safety extension was: 10.6 (1.4), 10.0 (1.6) and 9.2 (1.7) cm/year for 0.04/0.16 mg/kg/week (n=13), 0.08/0.16 mg/kg/week (n=15) and 0.16/0.16 mg/kg/week (n=14) somapacitan, respectively, versus 9.0 (2.3) cm/year for daily GH (n=11). Mean (SD) change from baseline in HV standard deviation score (SDS) was 8.04 (2.52), 6.21 (2.90) and 6.40 (3.04) for somapacitan, respectively, versus 6.58 (3.15) for daily GH. Compared with week 52, mean HV and HV SDS at week 104 were increased in children in the somapacitan 0.04/0.16 mg/kg/week and 0.08/0.16 mg/kg/week treatment groups. Height SDS values improved during the second year of treatment with somapacitan and daily GH, with the greatest change from baseline in the somapacitan 0.16/0.16 mg/kg/week treatment group. The mean (SD) change in height SDS from baseline to week 104 was 1.73 (0.76), 1.87 (0.81) and 2.18 (1.18) for somapacitan, respectively, versus 1.72 (0.65) for daily GH. The observed mean (SD) change in insulin-like growth factor-I (IGF-I) SDS from baseline was similar between the somapacitan 0.08/0.16 and 0.16/0.16 mg/kg/week treatment groups (3.15 [1.17] and 3.21 [1.12], respectively), and slightly higher compared with IGF-I SDS in the 0.04/0.16 mg/kg/week group (2.99 [1.05]) and the daily GH group (3.06 [1.26]). Mean IGF-I SDS values remained below the upper limit (+2) of the normal range for all treatment groups throughout the 104-week trial duration. Somapacitan was well tolerated at all doses investigated, with no new safety or local tolerability issues identified during the 104 weeks of treatment. In conclusion, at week 104, height-based outcomes were similar between somapacitan 0.16/0.16 mg/kg/week and daily GH, with comparable mean change in IGF-I SDS. Furthermore, the key improvements observed in the first year were maintained in the second year of the study.