title: Stratification of responders towards eculizumab using a structural epitope mapping strategy.
abstract: The complement component 5 (C5)-binding antibody eculizumab is used to treat patients with paroxysmal nocturnal hemoglobinuria (PNH) and atypical haemolytic uremic syndrome (aHUS). As recently reported there is a need for a precise classification of eculizumab responsive patients to allow for a safe and cost-effective treatment. To allow for such stratification, knowledge of the precise binding site of the drug on its target is crucial. Using a structural epitope mapping strategy based on bacterial surface display, flow cytometric sorting and validation via haemolytic activity testing, we identified six residues essential for binding of eculizumab to C5. This epitope co-localizes with the contact area recently identified by crystallography and includes positions in C5 mutated in non-responders. The identified epitope also includes residue W917, which is unique for human C5 and explains the observed lack of cross-reactivity for eculizumab with other primates. We could demonstrate that Ornithodorus moubata complement inhibitor (OmCI), in contrast to eculizumab, maintained anti-haemolytic function for mutations in any of the six epitope residues, thus representing a possible alternative treatment for patients non-responsive to eculizumab. The method for stratification of patients described here allows for precision medicine and should be applicable to several other diseases and therapeutics.
authors: KTH - Royal Institute of Technology, School of Biotechnology, Department of Proteomics and Nanobiotechnology, 106 91 Stockholm, Sweden.|KTH Center for Applied Proteomics, School of Biotechnology, KTH - Royal Institute of Technology, Stockholm, Sweden.
authors: Anna-Luisa
authors: AL
authors: Volk
authors: KTH - Royal Institute of Technology, School of Biotechnology, Department of Proteomics and Nanobiotechnology, 106 91 Stockholm, Sweden.|KTH Center for Applied Proteomics, School of Biotechnology, KTH - Royal Institute of Technology, Stockholm, Sweden.
authors: Francis Jingxin
authors: FJ
authors: Hu
authors: Swedish Orphan Biovitrum AB, 11276 Stockholm, Sweden.
authors: Magnus M
authors: MM
authors: Berglund
authors: Swedish Orphan Biovitrum AB, 11276 Stockholm, Sweden.
authors: Erik
authors: E
authors: Nordling
authors: Swedish Orphan Biovitrum AB, 11276 Stockholm, Sweden.
authors: Patrik
authors: P
authors: Strömberg
authors: KTH - Royal Institute of Technology, School of Biotechnology, Department of Proteomics and Nanobiotechnology, 106 91 Stockholm, Sweden.|KTH Center for Applied Proteomics, School of Biotechnology, KTH - Royal Institute of Technology, Stockholm, Sweden.|KTH - Royal Institute of Technology, Science for Life Laboratory, 17165 Stockholm, Sweden.|Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, DK-2970 Hørsholm, Denmark.
authors: Mathias
authors: M
authors: Uhlen
authors: KTH - Royal Institute of Technology, School of Biotechnology, Department of Proteomics and Nanobiotechnology, 106 91 Stockholm, Sweden.
authors: Johan
authors: J
authors: Rockberg
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology*; D001665:Binding Sites; D016466:CHO Cells; D003182:Complement C5 / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D051056:Complement Inactivating Agents / Q000494:pharmacology; D003412:Cricetulus; D018360:Crystallography, X-Ray; D018604:Epitope Mapping / Q000379:methods*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D000072417:Protein Domains
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D003182:Complement C5; D051056:Complement Inactivating Agents; C481642:eculizumab