An open-label extension of a phase 2 dose-finding study of once-weekly somatrogon vs. once-daily Genotropin in children with short stature due to growth hormone deficiency: results following 5 years of treatment.

OBJECTIVES: Somatrogon is a long-acting recombinant human growth hormone (GH) employed as a once-weekly treatment for children with GH deficiency (GHD). A 12-month, phase 2 study of once-weekly somatrogon vs. once-daily GH (Genotropin®) was initiated, after which participants could enroll into an open-label extension (OLE) evaluating the safety and efficacy of long-term somatrogon treatment. METHODS: There were five study periods, Periods I and II were 6 months each while Periods III, IV, and V were 12 months each. In the main study (Periods I and II), 53 prepubertal children with GHD were randomized to once-weekly somatrogon (0.25, 0.48, or 0.66 mg/kg/week) or once-daily Genotropin (0.034 mg/kg/day); 48 continued into the OLE, consisting of Period III (original somatrogon dose; Genotropin recipients randomized to one of three somatrogon doses), Period IV (somatrogon 0.66 mg/kg/week), and Period V (prefilled somatrogon pen [0.66 mg/kg/week]). RESULTS: At the end of Period III, the mean ± SD annual height velocity (HV) for 0.25, 0.48, and 0.66 mg/kg/week somatrogon groups was 7.73 ± 1.89, 7.54 ± 1.28, and 8.81 ± 1.12 cm/year, respectively; HV was sustained during Periods IV/V. Height SD scores (SDS) showed progressive improvement throughout the OLE, regardless of initial cohort assignment, approaching the normal range (-0.69 ± SD 0.87) at the end of Period V Year 1. Mild or moderate treatment-emergent adverse events were reported in 81.3% of participants, most unrelated to study drug. CONCLUSIONS: Up to 5 years of once-weekly somatrogon was well tolerated and resulted in sustained improvement in height SDS and delta height SDS in prepubertal short children with GHD.

A Randomized Phase 2 Study of Long-Acting TransCon GH vs Daily GH in Childhood GH Deficiency.

Context: TransCon Growth Hormone (GH) (Ascendis Pharma) is a long-acting recombinant sustained-release human GH prodrug in development for children with GH deficiency (GHD). Objective: To compare the pharmacokinetics, pharmacodynamics, safety, and efficacy of weekly TransCon GH to that of daily GH in prepubertal children with GHD. Design: Randomized, open-label, active-controlled study of three doses of weekly TransCon GH versus daily Genotropin (Pfizer). Setting: Thirty-eight centers in 14 European countries and Egypt. Patients: Prepubertal male and female treatment-naïve children with GHD (n = 53). Interventions: Subjects received one of three TransCon GH doses (0.14, 0.21, or 0.30 mg GH/kg/wk) or Genotropin 0.03 mg GH/kg/d for 26 weeks. Main Outcome Measures: GH and insulinlike growth factor-1 (IGF-1) levels, growth, adverse events, and immunogenicity. Results: Both GH maximum concentration and area under the curve were similar following TransCon GH or Genotropin administration at comparable doses. A dose response was observed, with IGF-1 standard deviation scores increasing into the normal range for all three TransCon GH doses. Annualized mean height velocity for the three TransCon GH doses ranged from 11.9 cm to 13.9 cm, which was not statistically different from 11.6 cm for Genotropin. Adverse events were mild to moderate, and most were unrelated to the study drug. Injection site tolerance was good. One TransCon GH subject developed a low-titer, nonneutralizing antibody response to GH. Conclusions: The results suggest that long-acting TransCon GH is comparable to daily Genotropin for GH (pharmacokinetics) and IGF-1 (pharmacodynamics) levels, safety, and efficacy and support advancement into phase 3 development.