C3 and neuromyelitis optica: Emerging therapies that target the complement system, such as pegcetacoplan for C3, eculizumab, an anti-C5 monoclonal antibody, and Avacopan, a specific C5aR1 inhibitor, have shown remarkable clinical efficacy in a range of conditions, including paroxysmal nocturnal hemoglobinuria, hemolytic uremic syndrome, anti-neutrophil cytoplasmic antibody-associated vasculitis, refractory generalized myasthenia gravis, and neuromyelitis optica spectrum disorder [472].