A single dose of GX-H9 was associated with a dose-dependent increase in mean peak GX-H9 and total exposure, investigators said, with much higher concentrations seen in the 0.3 mg/kg EOW group. “[A]fter gathering PK, PD and safety data from the 0.1 mg/kg weekly and 0.3 mg/kg EOW GX-H9 groups, the sponsor and members of the SMC agreed to use 0.2 mg/kg EOW for Group 3 rather than proceed with the planned dosage regimen of 0.3 mg/kg weekly and then 0.6 mg/kg EOW because significant increments in IGF-I were observed in the 0.3 mg/kg EOW GX-H9 group,” Ku and colleagues said.
After administration of 0.1 mg/kg weekly, 0.3 mg/kg, and 0.2 mg/kg EOW GX-H9 and daily administration of Genotropin, there was a significant increase in IGF-1 levels that peaked between 48 hours and 72 hours after the dose. In the 0.1 mg/kg GX-H9 group, the mean IGF-1 response sustained above baseline “over the intended dose interval” of 168 hours compared with 336 hours in the 0.2 mg/kg and 0.3 mg/kg EOW groups.
The authors noted potential limitations in the study, such as the small patient sample, an all-Asian demographic in the 0.1 mg/kg GX-H9 weekly group, and no significant changes in metabolic parameters at 12 weeks in patients randomly assigned GX-H9 and Genotropin. The investigators said a phase 3 clinical trial is under development that will have more patients and a longer treatment period to further study GX-H9.
Source: Ku CR, Brue T, Schilbach K, et al. Long-acting FC-fusion rhGH (GX-H9) shows potential for up to twice-monthly administration in GH-deficient adults. Eur J Endocrinol. 2018;179:169-179.