104,105 By the same principle, kidney transplantation may be an acceptable option for end-stage aHUS patients whose diseases are attributable to mutations in the membrane regulator MCP.91,106 Given the well-established role of complement in the pathogenesis of these kidney diseases, it is envisioned that systemic

or targeted local complement inhibition may represent a promising therapeutic strategy. In this context, the recent approval and successful clinical application of a first-in-class complement inhibitor Eculizumab, a humanized anti-C5 monoclonal antibody,107 SB525334 in vivo for treatment of the complement-mediated disease paroxysmal nocturnal haemaglobinuria108–110 is particularly encouraging. Based on a number of animal studies in which C5 deficiency or C5-blocking antibodies reduced renal injury,59,69,111 it may be anticipated that Eculizumab will prove to be efficacious for some, if not all, complement-mediated

kidney disorders as well. Indeed, two case reports on the successful treatments of paediatric aHUS patients with Eculizumab have already appeared in the literature112,113 and clinical trials on the use of Eculizumab in aHUS are currently underway.114 Other complement-based therapeutic strategies include chemical and biological agents that target additional complement components. A chemical inhibitor

for C3aR and two antagonists for C5aR, a cyclic hexapeptide and a recombinant C5a analogue, have been developed and shown to effectively Vemurafenib in vivo block anaphylatoxin-mediated inflammatory injury in a variety in vitro and in vivo studies MRIP including models of renal IRI and transplantation.115–118 A synthetic peptide, named Compstatin, with potent human C3-inhibiting activity has also been developed by phage display and shown to effectively shut down human complement activation in several experiments including an ex vivo model of hyperacute rejection of kidney xenotransplantation model.119–121 Compstatin is currently being evaluated in clinical trials for the treatment of AMD, a disease that also implicates abnormal AP complement activation.122 One of the concerns of targeting C3 with agents like Compstatin is that they obliterate the complement system completely, potentially compromising host defence and leaving the patients susceptible to infection. Because the AP complement is principally involved in many of the complement-mediated diseases, efforts have also been made to develop inhibitors that target the AP only. For example, two anti-C3b mAbs that specifically inhibit the AP C3 convertase with no activity on classical and lectin pathway complement activation have been described recently.