Long-acting FC-fusion rhGH (GX-H9) shows potential for up to twice-monthly administration in GH-deficient adults

Objective Hybrid Fc-fused rhGH (GX-H9) is a long-acting recombinant human growth hormone (GH) under clinical development for both adults and children with GH deficiency (GHD). We compared the safety, pharmacokinetics and pharmacodynamics of weekly and every other week (EOW) dosages of GX-H9 with those of daily GH administration in adult GHD (AGHD) patients. Design This was a randomized, open-label, active-controlled and dose-escalation study conducted in 16 endocrinology centers in Europe and Korea. Methods Forty-five AGHD patients with or without prior GH treatment were enrolled. Patients with prior GH treatments were required to have received the last GH administration at least 1 month prior to randomization. Subjects were sequentially assigned to treatment groups. Fifteen subjects were enrolled to each treatment group and randomly assigned to receive either GX-H9 or Genotropin (4:1 ratio). GX-H9 dosage regimens for Groups 1, 2 and 3 were 0.1 mg/kg weekly, 0.3 mg/kg EOW and 0.2 mg/kg EOW, respectively. All Genotropin-assigned subjects received 6 µg/kg Genotropin, regardless of treatment group. Main outcome analyses included measurements of serum insulin-like growth factor 1 (IGF-I), safety, pharmacokinetics, pharmacodynamics and immunogenicity. Results Mean GX-H9 peak and total exposure increased with an increase in dose after a single-dose administration. The mean IGF-I response was sustained above baseline over the intended dose interval of 168 h for the weekly and 336 h for the EOW GX-H9 groups. Safety profiles and immunogenicity were not different across the treatment groups and with Genotropin. Conclusions GX-H9 has the potential for up to twice-monthly administration.