Bioactivity and Pharmacodynamics of X002, A Follicle-Stimulating Hormone–IgG4 Fc Fusion Protein

Abstract

Current follicle-stimulating hormone (FSH) drugs meet safety criteria but have suboptimal efficacy, poor patient compliance, and high cost. Alternative FSH-like drugs would help to meet the high market demand. Here, we evaluated X002, an FSH–Fc fusion protein, for bioactivity and half-life in vitro and in vivo. In all cases, the effects of X002 were compared with those of a commercially available short-acting FSH recombinant hormone. First, female Kunming mice (age, 21 to 24 d) were stimulated with pregnant mare serum gonadotropin (PMSG) for 46 h, after which naked oocytes were harvested, treated with X002 or the comparison agent at 37 °C for 4 h, and then evaluated for germinal vesicle breakdown. Second, cumulus–oocyte complexes (COC) were collected from PMSG-stimulated mice and cocultured with X002 or the comparison agent for 14 h; the COC diameters were then measured, and the expression of genes involved in COC expansion were evaluated using quantitative RT-PCR analysis. Third, to assess the pharmacokinetics of X002, female Sprague–Dawley rats (age, 6 to 8 wk) were injected subcutaneously with X002 or the comparison agent; serum samples then were collected at various times and assessed via ELISA. Fourth, to evaluate X002 pharmacodynamics, 26-d-old female Sprague–Dawley rats were treated with X002 or the comparison agent; 84 h later, the rats were stimulated with human chorionic gonadotropin (hCG). At 12 h after hCG injection, euthanasia was performed. Ovaries were removed and weighed, and serum levels of estradiol and progesterone were measured. Finally, to assess superovulation, the oocytes in the fallopian tubes were counted at 108 h after in vivo treatment of rats with X002 or the comparison agent. The data show that X002, a long-acting agent, promoted germinal vesicle breakdown and COC expansion in vitro and in vivo ovarian weight gain and superovulation to a degree similar to the short-acting comparison agent.