Abstract: Objective To make a novel long-acting hCG-Fc fusion protein that could prolong hCG's serum half-life and improve the patients' compliance. Methods The expression vector was constructed by the gene engineering that contains the gene encoding hCG-Fc which Fc fragment was fused into the 3' end of hCG gene. The expression vector was transfected into CHO cells and stable clones were selected to express hCG-Fc fusion protein specifically. The serum free culture medium of cells grown was collected for protein purification using affinity based chromatography. The analysis of purified protein was performed as follow: molecular weight by SDS-PAGE, protein identity by Western blotting, activity in vitro by ELISA, activity in vivo by seminal vesicle weight gain assay, and serum half-life by single-subcutaneous injection into rats. Results The molecular weight of hCG-Fc fusion protein is similar to the theoretical size. The ELISA activity of hCG-Fc protein is 2 965 IU/mg and in vivo activity is 2 288 IU/mg. The serum half-life in rats is 174 h. Conclusions hCG-Fc fusion protein is active and functional based on its in vitro activity and in vivo activity. Pharmacokinetic study shows that its serum half-life is almost six times of the recombinant hCG's. This novel long-acting fusion protein can significantly reduce the times of injection and improve the patients' compliance of medicine, and also could have huge social and economic benefits.

Key words: Recombinant human chorionic gonadotropin (rhCG), Fc fusion protein, Long Acting, Pharmacokinetics