Neonatal Fc receptors (FcRns) recycle IgGs by preventing their lysosome degradation. As this process also enhances half-life of pathogenic auto-IgG, inspired from the mechanisms of intravenous immunoglobulin, several inhibitors of IgG-FcRn interface have been conceived for treating autoimmune diseases. Among them, the high-affinity FcRn-binding engineered Fc molecule efgartigimod has recently completed phase I clinical trial.