Antisense and siRNA Drug Delivery Using Antibody Fragments

Antisense oligonucleotides (ASO) and short interfering RNA (siRNA) are nucleic acid based compounds designed to specifically inhibit the biosynthesis of a single protein by interfering with translational processes. While these concepts are valuable tools in molecular biology research, their use as drugs has to date been hampered by unsufficient pharmacokinetic properties and unspecific actions. Several clinical trials of first generation antisense oligonucleotides failed in phase III recently, indicating persistent need to improve the pharmacodynamics of this compound class. The aim of the project is to modify oligonucleotides so that cell uptake is improved both in vitro and in vivo. Covalent attachment an complexation of antibody fragments to oligonucleotides is proposed to faciliate membrane permeation. During the research stay, conjugates of antitumor oligonucleotides with recombinant antibodies and synthetic ankyrin-repeat proteins directed against the epithelial cell adhesion molecule (Ep-CAM) or the oncoprotein Her-2 will be synthesized. The conjugated or complexed proteins presumably increase cell uptake as well as adding a specific tumor targeting effect by being actively internalized in cancer cells, where the corresponding antigens are overexpressed. As linker, an acid-labile hydrazone tether is proposed. The bond between oligonucleotide and antibody is easily cleaved in the acid environment of the tumor endosome setting free the oligonucleotide and facilitating re-release from endosomal compartments. Additionally, immunoliposomes loaded with oligonucleotides will be examined. The efficacy of these conjugates and complexes will subsequently be determined in several in vitro assays. The extent of cell uptake and the exact localization in the cell will be studied by confocal laser microscopy. Research results are expected to contribute to the development of highly efficient and safe nucleic acid type drugs.