Eculizumab is an anti-C5 humanized monoclonal antibody that binds to C5, preventing its cleavage into C5a and C5b. Thus, eculizumab disables the terminal complement pathway and inhibits MAC-mediated intravascular hemolysis. It is first line therapy in atypical hemolytic uremic syndrome (aHUS) and paroxysmal nocturnal hemoglobinuria (PNH).