Eculizumab (Soliris, Alexion Pharmaceuticals), an anti-C5 IgG, is the first complement drug with potent activity in assays like C5 binding, and C5 cleavage inhibition along with hemolysis inhibition, and has been approved for the treatment of PNH (36). The gene discussed is C5; the disease is paroxysmal nocturnal hemoglobinuria.