A Modular Polymer Enhancer Promotes AAV Transduction and Circumvents Preexisting Immunity in Nonhuman Primates

Adeno-associated virus (AAV) gene therapy is frequently hindered by dose-limiting toxicities and preexisting neutralizing antibodies (nAbs). Here, we evaluate enhancer polymer (ePL), a cargo-less poly(L-lactic-co-glycolic acid) nanoparticle, the systemic administration of which demonstrated biocompatibility in nonhuman primates (NHPs) and generated a protransduction serum secretome that significantly enhanced AAV uptake in human iPSC-derived cardiomyocytes. Proteomic analysis of human peripheral blood mononuclear cell-derived secretomes identified a transient upregulation of AAV-entry factors, including ITGB3, alongside a downregulation of inflammatory cytokine pathways. Mechanistically, ePL-stimulated macrophages release a paracrine secretome that triggers the rapid, transient degradation of hepatic insulin receptor substrate 2 and subsequent AKT inhibition in liver and isolated primary mouse hepatocytes. Additionally, ePL attenuated the levels of NHP-derived nAbs in vitro and in a mouse-NHP xenotransfusion model without depleting total systemic immunoglobulins. Finally, ePL reduced Immunoglobulin G (IgG) secretory capacity of splenic B cells, suggesting a mechanistic link by which levels of nAbs are likely attenuated. Together, these findings highlight ePL as a promising supporting agent to improve AAV gene transfer, warranting its further optimization for clinical translation.