AAV delivered lysosome-targeting chimeras mediate sustained antibody depletion in vivo.

Immunoglobulin G (IgG) is a critical effector of the adaptive immune system, but IgG autoantibodies against self-antigens drive pathology across a wide range of autoimmune diseases. Lowering circulating IgG is a validated and promising therapeutic avenue. Here we developed genetically-encoded lysosome targeting chimeras (GELYTACs) that target circulating IgGs for clearance and degradation. The GELYTACs comprised two protein modules derived from insulin-like growth factor 2 (IGF2) and an IgG-binding nanobody, respectively, and mediated clearance of plasma IgG via the lysosomal trafficking receptor IGF2R. To achieve long-lasting IgG depletion, we encoded GELYTACs in an AAV gene therapy vector and established continuous expression in mice. We also developed conditional GELYACs that are activatable with disease-specific proteases or small molecule drugs and show that GELYTACs can be secreted from cellular therapies. This work establishes GELYTACs as a possible therapeutic modality that is deliverable using genetic medicine approaches.