Supplementary Material for: Once-weekly Lonapegsomatropin was Efficacious and Well Tolerated in Chinese Children with Growth Hormone Deficiency: Results from a Phase 3 Randomized Trial

Introduction: Lonapegsomatropin, a prodrug of somatropin, is approved for once-weekly treatment of paediatric growth hormone deficiency (GHD) in the USA and Europe. Here, we report the first trial to assess the efficacy and safety of weekly lonapegsomatropin compared to daily somatropin in treatment-naive Chinese children with GHD. Methods: The briGHt trial was a randomized, open-label, active-controlled, 52-week, phase 3 trial (NCT04326374; CTR20200399) conducted at 17 sites across China. Treatment-naive, prepubertal children with GHD were enrolled and randomized 2:1 to either lonapegsomatropin 0.24 mg hGH/kg/week or equivalent weekly dose of daily somatropin 0.034 mg/kg/day. The primary endpoint was annualized height velocity (AHV) at week 52. Secondary endpoints included change in height standard deviation score (∆HT SDS) from baseline, insulin-like growth factor 1, and safety. Results: 153 participants received treatment. Least-squares (LS) mean ± standard error (±SE) of AHV at week 52 was 10.66 ± 0.22 cm/year for weekly lonapegsomatropin and 9.75 ± 0.26 cm/year for daily somatropin; weekly lonapegsomatropin demonstrated non-inferiority and superiority over daily somatropin, with a difference of 0.91 ± 0.28 cm/year (95% confidence interval: 0.37–1.45; p = 0.0010). LS mean (±SE) of ∆HT SDS was 1.01 ± 0.04 for weekly lonapegsomatropin and 0.83 ± 0.05 for daily somatropin at week 52, favouring lonapegsomatropin from week 13 (p < 0.05) onward. The safety profile was similar between treatment groups. Conclusions: Weekly lonapegsomatropin demonstrated non-inferiority and superiority in efficacy compared to daily somatropin among treatment-naive Chinese children with GHD. The treatment groups showed comparable safety and tolerability profiles.