1:Vivet Therapeutics S.L., Spain; 2:Division of Gene Therapy and Regulation of Gene Expression, CIMA, University of Navarra, Pamplona, Spain; 3:Institute for Sanitary Research (IdiSNA), Pamplona, Spain; 4:Vivet Therapeutics S.A.S., Paris, France

Pre-existing neutralizing antibodies (NAbs) to adeno-associated viruses (AAVs) remain an impediment for systemically administered AAV-mediated gene therapy treatment in many patients and various strategies are under investigation to overcome this limitation. Here, IgG degrading enzymes (Ides) derived from bacteria of the genus Streptococcus were tested for their ability to cleave human IgG and allow AAV-mediated transduction in individuals with pre-existing NAbs. Cleavage activity of three different Ides was evaluated in vitro in serum from different species. Passively immunized mice or non-human primate (NHP) with naturally occurring anti-AAV NAbs were used to define the optimal IdeS dose and administration window for AAVAnc80 and AAV8 vectors in mice and AAV3B in NHPs. The selected candidate, IdeS, was found to be highly efficient at cleaving human IgG, less efficient against NHP IgG and inefficient against mouse IgG. In vivo, we observed differences on how IdeS affected liver transduction in the presence of NAbs depending on the AAV serotype. For AAVAnc80 and AAV3B the best transduction levels were achieved when the vector is administered after IgG NAb digestion products are cleared from circulation. However, for AAV8 we only observed a modest and transient inhibition of transduction by IdeS cleavage products. Preconditioning with IdeS represents a unique treatment opportunity for patients primarily excluded from participation in gene therapy clinical trials due to elevated circulating anti-AAV NAb levels. However, careful determination of the optimal IdeS dose and timing for the administration of each AAV serotype is essential for optimal transduction