C5 and atypical hemolytic-uremic syndrome: Complement-active drugs are available and already in use.35For instance, eculizumab, which inhibits the cleavage of C5 by the C5 convertase into C5a, has been clinically established for the treatment of aHUS (atypical hemolytic uremic syndrome) and for PNH (paroxysmal nocturnal hemoglobinuria).36Indeed, several novel pharmacological approaches have recently been introduced, i.e., Pegcetacoplan37or Avacopan,38a C5aR1 inhibitor, to the clinic.