title: Controlling the anaphylatoxin C5a in diseases requires a specifically targeted inhibition.
abstract: The terminal complement split product C5a has been described as an important mediator in inflammatory diseases. C5a is generated upon cleavage of C5 and earlier research suggests that, besides the known C5 convertases formed upon activation of the complement pathways, various enzymes could activate C5 directly. We demonstrate that eculizumab effectively blocks C5 activation when mediated by C5-convertase formation, but fails to block C5a generation resulting from direct enzymatic cleavage by trypsin and thrombin. C5a generated by these enzymes is shown to be fully biologically functional and can be blocked by IFX-1, a specific monoclonal anti-human C5a antibody. We further report clinical cases of atypical hemolytic uremic syndrome (aHUS) and C3 Glomerulonephritis (C3GN) patients under treatment with eculizumab presenting substantially elevated C5a levels. Thus, blocking the C5 convertase mediated activation of C5 may not be efficient to control C5a-mediated effects in human disease and that a targeted approach is warranted.
authors.affiliation: InflaRx GmbH, Jena, Germany. Electronic address: Niels.Riedemann@inflarx.de.
authors.forename: Niels C
authors.initials: NC
authors.lastname: Riedemann
authors.affiliation: InflaRx GmbH, Jena, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Habel
authors.affiliation: InflaRx GmbH, Jena, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Ziereisen
authors.affiliation: InflaRx GmbH, Jena, Germany.
authors.forename: Marlen
authors.initials: M
authors.lastname: Hermann
authors.affiliation: InflaRx GmbH, Jena, Germany.
authors.forename: Conny
authors.initials: C
authors.lastname: Schneider
authors.affiliation: Institute of Immunology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Cyrill
authors.initials: C
authors.lastname: Wehling
authors.affiliation: Institute of Immunology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Kirschfink
authors.affiliation: Department of Pediatric Immunology, University Hospital Jena, Jena, Germany.
authors.forename: Karim
authors.initials: K
authors.lastname: Kentouche
authors.affiliation: InflaRx GmbH, Jena, Germany. Electronic address: renfeng.guo@inflarx.de.
authors.forename: Renfeng
authors.initials: R
authors.lastname: Guo
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology* / Q000627:therapeutic use; D065766:Atypical Hemolytic Uremic Syndrome / Q000188:drug therapy / Q000276:immunology*; D050577:Complement C3-C5 Convertases / Q000276:immunology; D015936:Complement C5a / Q000276:immunology*; D005921:Glomerulonephritis / Q000188:drug therapy / Q000276:immunology*; D006801:Humans; D013917:Thrombin / Q000276:immunology; D014357:Trypsin / Q000276:immunology; D015054:Zymosan / Q000494:pharmacology
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D015936:Complement C5a; D015054:Zymosan; C481642:eculizumab; D050577:Complement C3-C5 Convertases; D014357:Trypsin; D013917:Thrombin
keywords: C5a blockade; Complement activation; Eculizumab; Thrombin; Trypsin