Novel synthetic gene transfer vectors for metabolic liver therapy

The world of medicine experienced a new innovation in the way how patients can be treated by the emergence of gene therapy, which demonstrated its enormous potential during the Covid-19 pandemic. Ever since, gene therapy is a much-discussed topic that arrived in almost every household. But what exactly is gene therapy? Gene therapy refers to the ability to alter the regulation of genes or genes themselves via inhibition, expression or modification of genes. The genetic information is encoded and mediated in so-called nucleic acids, namely DNA and RNA. RNA transmits the genetic information which is stored in the DNA in the form of genes for protein biosynthesis. A defect within this sequence leads to defective or no expression of proteins, which can cause severe harm to affected individual.
Inheritable diseases are a medical condition that is passed down through defective DNA from one generation to the next. This group of disorders often lacks effective treatment options and would therefore greatly profit from gene therapy. In this context, the liver represents an ideal target organ for the development of gene therapeutic treatments, since it harbours numerous inheritable metabolic disorders.
The challenge in the field of gene therapy is the delivery of therapeutic nucleic acids, which are unstable and rapidly degraded inside of the body. For stabilization, viruses are widely used as conventional transport systems. However, these systems are limited by serious safety concerns resulting from the incorporation of nucleic acid material into the genome, as well as the inherent immunogenic properties of the virus. Moreover, viruses are unsuitable for addressing numerous diseases due to constraints related to the size of
the cargo that can be delivered.
The aim of this thesis therefore focused on the exploration of various non-viral materials for the delivery of non-integrating DNA to the liver, which led to different projects: First, non-viral gene delivery technologies were evaluated and limitations for clinical translation were identified. Second, strategies were developed to address these limitations including local or systemic administration of polymeric and lipid formulations.
By conducting this work, essential hurdles were identified, such as limited understanding on cellular processing of nanoparticles, lack of advanced carriers that address extra- and intracellular obstacles, and the absence of stable DNA derivatives. Although promising polyethylenimine-chitosan polymers require solutions to mitigate the cytotoxic effects associated to the cationic charge, while current lipid nanoparticles formulations are not sufficiently optimized for DNA delivery and lack specific delivery.
The research carried out during this thesis represents the first step towards transport of therapeutic non-integrative long-acting DNA as a non-viral alternative to conventional viral gene therapy approaches. Further improvement of both, the carrier system and the DNA cargo, will offer new therapeutic options to ease the pain of patients suffering from inheritable metabolic liver disease and beyond.