Thèse de doctorat en Pharmacochimie
Soutenue le 27-11-2015
à Sorbonne Paris Cité , dans le cadre de École doctorale Médicament, toxicologie, chimie, imageries (Paris) , en partenariat avec Université Paris Descartes (établissement de préparation) .
Le président du jury était Sylviane Giorgi-Renault.
Pas de résumé
Recently targeted therapies appeared as attractive alternatives to classical antitumoral treatments. The approach, developed on the concept of targeting drug to cancer cells, aims to spear normal tissues and decrease the side effects. This doctoral dissertation focuses on developing new anticancer targeted treatments in the field of chemotherapy and cancer immunotherapy by exploiting an original targeting moiety, the B subunit of Shiga toxin (STxB). Its specific properties, such as, recognition with its receptor Gb3 overexpressed in cancer cells or in antigen-presenting cells, its unconventional intracellular trafficking, guided the choice of this protein as targeting carrier. This project is based in the use of copper-free Huisgen [3+2] cycloaddition as a coupling method, which led to successful preparation of various conjugates for their respective applications. The concept was first validated by STxB-biotin conjugate. The high yield of the reaction and the compatibility between the targeting carrier and the chemical ligation promoted the design of conjugates for chemotherapy and immunotherapy. Two therapeutical optimizations of previously developed strategy in STxB drug targeting delivery were investigated: synthesis of multivalent drug-conjugates and synthesis of conjugates containing a highly potent anticancer agent. Both approaches exploited three anticancer agents: SN38, Doxorubicin and Monomethyl auristatin F. The disulfide spacer, combined with various self-immolative systems, insured drug release. Two cytotoxic conjugates STxB–doxorubicin (STxB-Doxo) and STxB-monomethyl auristatin F (STxB-MMAF) were obtained in very high yield and demonstrated strong tumor inhibition activity in the nanomolar range on Gb3-positive cells. Based on the results the STxB-MMAF conjugate was investigated on a mouse model. The project aimed also to develop STxB bioconjugates for vaccine applications. Previous studies used B subunit as a targeting carrier coupled to an antigenic protein in order to induce a more potent immune response against cancer. The conjugates were prepared using a commercial linker, requiring modifying the antigen at first place, or by oxime ligation, where slightly acidic conditions promoted the coupling. Thus, the work presented herein proposed an alternative ligation via copper-free click chemistry especially for more sensitive antigenic proteins. Various types of conjugates were synthesised and investigated for their immune stimulation properties. The STxB targeting strategy was also applied to the development of a new vaccine based on coupling the targeting carrier to alpha-GalCer, one of the most potent immune stimulating agents known. The work focused on the synthesis of functionalised alpha-Galcer with an azide handle.