Fuad Fares
Department of HumanBiology, Faculty of Natural Sciences, University of Haifa, and Department of Molecular Genetics, Carmel Medical Center, Haifa, Israel
One major issue regarding the clinical use of many peptides is their short half-life due to the rapid clearance from the circulation. To overcome this problem, we used overlapping PCR technique to add the signal sequence of O-linked oligosaccharides to the coding sequence of glycoprotein hormones. The used cassette gene contains the sequence of the carboxyl-terminal peptide (CTP) of human chorionic gonadotropin β (hCGβ) subunit. It was postulated that the O-linked oligosaccharides add flexibility, hydrophilicity, stability and prevent plasma clearance and thus increasing the half-life of the protein in circulation. Using this strategy we succeeded to ligate the CTP to the coding sequence of follitropin (FSH), thyrotropin (TSH), erythropoietin (EPO) growth hormone (GH) and thus to increase the longevity and bioactivity of these proteins in-vivo. Interestingly, the new analog of FSH was found not immunogenic in humans and it was approved by the European Commission (EC) for treatment of fertility. In addition, our results indicated that long acting GH is not toxic in monkeys and the results from clinical trials phases I and II seem to be promising. Designing long acting peptides will diminish the cost of these drugs and perhaps reduce the number of injections in the clinical protocols.
Deletion of the N-linked oligosaccharides from hTSH significantly reduced its activity in vitro and in vivo. Moreover, deglycosylated TSH compete with hTSH and human Thyroid Stimulating immunoglobulin (TSI) in a dose dependent manner. These variants may offer a novel therapeutic strategy in the treatment of hyperthyroidism and Grave’s disease.
Keywords: Glycoprotein,follitropin,thyrotropin and erythropoietin.