C5 and paroxysmal nocturnal hemoglobinuria: We propose also that novel drugs that inhibit the C5a–C5aR axis, such as the L-aptamer AON-D21 or C5aR antagonists, can find practical application in the treatment of PNH, aHUS or other clinical states when complement cascade is activated [32] in addition to eculizumab [29, 30, 33, 34] or compstatin [35, 36].