An immune system, enhanced by the immunotherapy, is able to recognize and destroy tumor cells. In vivo, cancer cells are able to develop mechanisms for tumors to resist and escape the immune system. Among these, two enzymes are the key players: indoleamine 2,3- dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO). These enzymes catalyze the breakdown of an essential amino acid, L-tryptophan (L-trp) in kynurenine, to form different physiologically active molecules. This results in a local decrease in L-trp, which is significantly affecting the proliferation of T lymphocytes. The activity of IDO and TDO is particularly immunosuppressive, justifying this choice of therapeutic targets for cancer therapy. In this work, we will focus on TDO, to date, the unique reference inhibitor, the fluoroindole 680C91. Nevertheless, in vivo, it has a poor oral bioavailability. Therefore, the aim of this thesis is to design new specific inhibitors of TDO and characterize their interactions with the enzyme using theoretical and experimental approaches. Once the compounds synthesized, a global cellular assay has identified promising inhibitors. The first series has, throughout a fundamental study, led to the characterization of three chloride isomers namely: 5, 6, 7-chloro-3-(2-pyridin-3-ylvinyle)-1H-indole, resulting into a better understanding of the influence of the position of a halogen on the structural and physico-chemical properties. This study highlights the crystalline packing and intermolecular interactions between different molecules of the lattice. Moreover, a study of electronic properties exhibited the dipole moment and the electrostatic potential. Finally, the model study of inhibition was correlated with the biological results, the IC50 on hTDO. The second set of molecules has two acid derivatives of the vinyl-1H-indoles series. The characterization, in vitro, of these molecules has shown that they are not substrates of hTDO. It also permits to determine their Ki. Additionally, the IC50 of these molecules on cells was evaluated. Then, structural and physico-chemical characterization provided different properties, ie, pKa, solubility, selectivity and stability. Finally, crystallographic assays were conducted in the presence of active and purified enzyme (rmTDO), alone or in complex with the inhibitor, in order to better understand the interactions within the active site. All these studies have highlighted the most promising molecules in terms of inhibition but also pharmaceutically. The latter has been studied in vivo with mices and shows promise.
|Date of Award
|30 Jan 2012
|Johan Wouters (Supervisor), Steve Lanners (President), BERNARD MASEREEL (Jury), Moreno Galleni (Jury) & Raphaël Frederick (Jury)