PhD defense of Francesco Terzani

and carried out under the supervision of Dr. Evelyne Chelain and Prof. Julien Pytkowicz
on Thursday, December the 8th in amphi F.009 of the Neuville campus. 

Cathepsin D is an aspartyl protease which is found in almost all the cells and tissues of mammals. The physiological functions of this enzyme are mainly the metabolic degradation of intracellular proteins, activation and degradation of polypeptide hormones and growth factors and regulation of programmed cell death. However, since several years it has been demonstrated a correlation between this enzyme and several types of diseases. In particular the scientific community focused on the relation between increased level of Cathepsin D and certain types of cancer. Several works showed a direct implication of the increased level of Cathepsin D with poor prognosis and formation of metastasis. Thus, the use of inhibitors of Cathepsin D could be a promising strategy for the treatment of cancer. Several inhibitors of this enzyme are known, both natural and synthetic compounds. Among them Pepstatin A, a penta-peptide containing two residues of the non-natural β-hydroxy--amino acid Statin, is the best inhibitor known with a sub-nanomolar IC50. Nevertheless, due to its poor metabolic stability, poor selectivity and poor pharmacokinetic properties, its use for the treatment of cancer is limited. The expertise of our laboratory in the asymmetric synthesis of fluorinated amino acids allowed us to develop a new series of fluorinated analogs of Pepstatin A by replacing parts of this compound with fluorinated scaffolds. The introduction of fluorinated amino acids in the peptidic scaffold of Pepstatin A, in fact, could improve the metabolic stability, the pharmacokinetic properties the selectivity despite other aspartyl proteases and open the way to ¹⁹F NMR based functional assays. In this context, we designed, synthesized and evaluated several fluorinated peptide inhibitors of Cathepsin D and we showed that the replacement of a N-terminal Valine with a D- Trifluoromethionine in the structure of Pepstatin A leads to a very potent and selective analogue. At the same time, we designed and synthesized a fluorinated peptide substrate that allowed us to develop a ¹⁹F NMR FABS (Fluorine Atoms for biochemical screening) based assay to test the biological activity of our compounds towards aspartyl proteases. The results have been compared with a commercial available fluorescence-based Cathepsin D inhibitors screening kit.