ESPE Abstracts

Background: TransCon GH is a novel sustained-release recombinant human GH (somatropin) prodrug in development for children with GH deficiency (GHD). It is designed to release unmodified GH and intended to provide comparable efficacy, safety, tolerability, and immunogenicity to daily GH with once-weekly dosing. Based on results from a phase 2 trial, which demonstrated comparable efficacy (annualized height velocity for TransCon 0.21 mg GH/kg per week of 12.9 cm/year vs 11.6 cm/year for the same dose of daily GH), the ongoing randomized phase 3 global heiGHt trial is designed to investigate the safety, tolerability, and efficacy of weekly TransCon GH vs standard daily GH over 52 weeks in 150 treatment-naive prepubertal children with GHD. Enrollment is nearing completion.

Methods: Subjects are randomized in a 2:1 ratio and receive either once-weekly TransCon GH 0.24 mg GH/kg per week or dose-equivalent once-daily somatropin for 52 weeks. Key baseline demographic variables include age, gender, height SDS, IGF1 SDS, peak stimulated GH, and bone age delay. Endpoints include efficacy (height SDS and changes in serum IGF1 and IGFBP-3 levels), safety, and immunogenicity.

Results: We will present key baseline demographic variables. Beyond simply descriptive purposes, these data also have important implications as predictors for annualized height velocity (HV) based on published literature. Therefore, we will also evaluate baseline characteristics to better understand expected annualized HV of subjects while receiving GH treatment. A power calculation will be presented based on the final sample size of the heiGHt Trial.

Conclusion: Baseline variables can provide important insights about the study population and how well they will respond to GH therapy, as well as how representative the study population may be to the general population who may be eligible for treatment in the future. The results of the phase 2 TransCon GH trial, which included a daily GH as an active control, informed the phase 3 heiGHt Trial design, allowing the optimization of statistical power. The heiGHt Trial is well powered to demonstrate noninferiority between TransCon GH and daily GH, and its demographics are in the range of other pivotal GH trials.