RESUMEN
Extensive clinical data from liver-mediated gene therapy trials have shown that dose-dependent immune responses against the vector capsid may impair or even preclude transgene expression if not managed successfully with prompt immune suppression. The goal of this preclinical study was to generate an adeno-associated viral (AAV) vector capable of expressing therapeutic levels of B-domain deleted factor VIII (FVIII) at the lowest possible vector dose to minimize the potential Risk of a capsid-mediated immune response in the clinical setting. Here, we describe the studies that identified the investigational agent SPK-8011, currently being evaluated in a phase 1/2 study (NCT03003533) in individuals with hemophilia A. In particular, the potency of our second-generation expression cassettes was evaluated in mice and in non-human primates using two different bioengineered capsids (AAV-Spark100 and AAV-Spark200). At 2 weeks after gene transfer, primates transduced with 2 × 1012 vg/kg AAV-Spark100-FVIII or AAV-Spark200-FVIII expressed FVIII antigen levels of 13% ± 2% and 22% ± 6% of normal, respectively. Collectively, these preclinical results validate the feasibility of lowering the AAV capsid dose for a gene-based therapeutic approach for hemophilia A to a dose level orders of magnitude lower than the first-generation vectors in the clinic.
RESUMEN
Neutralizing antibodies to adeno-associated virus (AAV) vectors are highly prevalent in humans1,2, and block liver transduction3-5 and vector readministration6; thus, they represent a major limitation to in vivo gene therapy. Strategies aimed at overcoming anti-AAV antibodies are being studied7, which often involve immunosuppression and are not efficient in removing pre-existing antibodies. Imlifidase (IdeS) is an endopeptidase able to degrade circulating IgG that is currently being tested in transplant patients8. Here, we studied if IdeS could eliminate anti-AAV antibodies in the context of gene therapy. We showed efficient cleavage of pooled human IgG (intravenous Ig) in vitro upon endopeptidase treatment. In mice passively immunized with intravenous Ig, IdeS administration decreased anti-AAV antibodies and enabled efficient liver gene transfer. The approach was scaled up to nonhuman primates, a natural host for wild-type AAV. IdeS treatment before AAV vector infusion was safe and resulted in enhanced liver transduction, even in the setting of vector readministration. Finally, IdeS reduced anti-AAV antibody levels from human plasma samples in vitro, including plasma from prospective gene therapy trial participants. These results provide a potential solution to overcome pre-existing antibodies to AAV-based gene therapy.