Immunomodulation in AAV gene therapy - Abstract Recombinant AAV vectors have emerged as promising gene delivery vehicles in the treatment of monogenic disorders. With 6 different FDA approved AAV-based therapies, many additional disease targets requiring systemic dosing continue advancing towards the clinic. However, immune responses arising from prior natural AAV exposure or nascent exposure to recombinant AAV vectors dosed in human subjects poses a major challenge. Evidence from multiple gene therapy clinical trials confirms that high vector doses can trigger cytokine release leading to nausea, fever, and vomiting, and manifest in liver toxicity (elevated enzymes). In some patients, complement activation following systemic AAV dosing has been shown to result in thrombotic microangiopathy (TMA) and acute kidney injury (atypical hemolytic uremic syndrome-like), thrombocytopenia, myocardial injury, and even death. Many of these adverse reactions can be attributed to AAV capsid-antibody interactions highlighting a major (if not predominant) role for humoral immunity. Prophylactic measures or symptom management have generally included plasmapheresis, administration of tapering, high doses of glucocorticosteroids, hemodialysis, platelet transfusion, different drugs or monoclonal antibodies to block complement/B cell activation or induce B cell depletion amongst others. More recently, preclinical testing of agents such as Imlifidase or Vyvgart for promoting IgG clearance has been initiated. However, these current management or mitigation strategies for these clinical sequalae are applied on a case-by-case basis with no specific consensus immunomodulatory regimens (IMRs) in place. Thus, there is a clear and urgent need to better understand, preclinically model and manage these complex sequalae (focus of the current proposal). To this end, our lab recently engineered a novel immunomodulatory agent, IceMG – a recombinant, dual activity protease that can selectively and efficiently cleave human and monkey IgG/IgM. Here, we propose to build on our exciting findings and validate that IceMG is a potent blocker of complement activation as well as modulator of B cell signaling pathways in human models in vitro and humanized mice as well as non-human primates in vivo, thereby charting a path for first-in-human Phase I trials utilizing this IMR. Further, we will engineer and characterize next generation immunomodulators (IceRx) for clinical translation. If successful, the current proposal will enable development of new and improved IMR, essential for the success of AAV gene transfer vectors in the clinic. The proposed strategies may also pave the path for clinical applications in autoimmune disease and organ transplantation.
