Development of an Effective Strategy to Block Nab Activity for AAV Brain Transduction

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Adeno-associated virus (AAV) vectors have been successfully employed in patients with rare neurological diseases. Recently, two AAV based gene therapy drugs have been approved by the FDA, Luxturna been valued at $850,000 with a one-time application for blindness and Zolgensma at $2,100,000 for spinal muscle atrophy. AAV vector mediated gene therapy has shown to be a potentially huge market. Although successful in clinical studies for neurological disorders, one of the major concerns for effective AAV brain application is high prevalence of neutralizing antibody (Nab) in humans. In the general human population, over 95 % of individuals are infected by AAV and, on average, 50 % of them develop Nabs. The inhibition effect of Nabs on AAV brain transduction has been well documented regardless of delivery routes (direct intra-brain injection or systemic administration). Several approaches have been exploited to escape AAV Nabs, including chemical modification, use of different AAV vector serotypes, AAV capsid engineering, and biological depletion of Nab titer (empty capsid utilization, B cell depletion, plasma-apheresis, and Ig proteases). Generally, these approaches have low efficiency, unwanted side effects, or AAV tropism change. Recently, Nabgen has developed a vector independent protein-based strategy to universally block Nabs using a unique mycoplasma derived protein, termed Protein-M. Protein-M is able to interact with immunoglobulin from any species without antigen dependence by binding to variable regions on the antibody light and heavy chains. Using human IVIG and serum from AAV immunized mice, we have found that Protein-M reduced AAV vector neutralization over 100 fold when compared to control group without Protein-M in vitro. Most importantly, we have observed that Protein-M was able to retain AAV transduction over 1000 fold in mice with adoptive transfer of Nab positive serum. So far, this is the most effective strategy to evade AAV Nabs. To explore the application of Protein-M in patients with AAV brain targeted therapy, it is imperative to address the efficacy of Protein-M to protect AAV from Nabs for brain transduction in subjects with Nabs. In this proposal, we will first study the effect of Protein- M co-administered with AAV vectors on AAV Nab blockage via direct injection into the brain in mice with pre- immunization of AAV (Aim 1). Next, we will study the effect of Protein-M via systemic injection on brain transduction after direct delivery of AAV vectors (Aim 2). If successful, this novel and effective technology will extend the benefits of AAV targeted gene therapy to every patient with brain disorders and AAV Nabs.