Pharmacodynamics, pharmacokinetics, and toxicology of Fc-growth hormone fusion protein in macaques

Abstract

Purpose

Growth hormone (GH) therapy for GH deficiency is used to treat multiple conditions. However, the short half-life of GH necessitates frequent dosing, which limits patient adherence. Fc fusion proteins, created by binding an active peptide to the Fc portion of IgG, are known to prolong the plasma half-life of the peptide. Pharmacodynamics and pharmacokinetics of Fc-GH in rats have been reported; however, studies in primate models are lacking. Therefore, in this study, we aimed to investigate the pharmacodynamics, pharmacokinetics, and toxicology of Fc-GH in rhesus and crab-eating macaques.

Methods

In rhesus macaques, Fc-GH was injected subcutaneously at 0.8, 1.6, and 3.2 mg/kg and intravenously at 1.6 mg/kg. The 1.6 mg/kg subcutaneous dose was administered five times, once every 7 days; other doses were administered as single injections for pharmacodynamic and pharmacokinetic assessments. In crab-eating macaques, potential toxicity was evaluated after single subcutaneous injections at 30, 45, and 62.5 mg/kg and repeated injections at 3, 10, and 30 mg/kg once every 7 days, followed by an 8-week recovery.

Results

No adverse events were observed following Fc-GH administrations. Fc-GH achieved C_max slowly after subcutaneous administration and rapidly after intravenous administration, with plasma levels being maintained over time. In rhesus macaques, the half-life increased dose-dependently: 23.72 ± 2.17 h (0.8 mg/kg), 49.44 ± 14.77 h (1.6 mg/kg), and 76.07 ± 13.19 h (3.2 mg/kg). After five injections of 1.6 mg/kg, the half-life of Fc-GH was 60.42 ± 18.29 h. Insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 3 (IGFBP-3) levels significantly increased and remained elevated for 28–42 days after Fc-GH injections. In crab-eating macaques, no Fc-GH accumulation was observed. The maximum tolerated single subcutaneous dose was 62.5 mg/kg; no adverse effects were observed at 30 mg/kg during repeated administration over 29 injections with an 8-week recovery.

Conclusions

Fc-GH demonstrated favorable pharmacokinetics and pharmacodynamics in macaques, significantly extending the half-life and enhancing IGF-1 and IGFBP-3 levels without adverse effects. These findings suggest Fc-GH as a promising long-acting GH therapy that could improve patient adherence.