title: Extravascular hemolysis and complement consumption in Paroxysmal Nocturnal Hemoglobinuria patients undergoing eculizumab treatment.
abstract: Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired hemolytic anemia characterized by complement-mediated intravascular hemolysis that is effectively treated with eculizumab. However, treatment responses are reported heterogeneous with some patients presenting residual hemolysis and requiring RBC transfusions. Recent reports have shown that both extravascular hemolysis and incomplete C5 blockade can explain these suboptimal hematological responses. Here we have tested our eculizumab-treated PNH patients (n=12) for signs of hemolysis and assessed complement biomarkers. Patients were also genotyped for complement receptor 1 (CR1, CD35) and C5 polymorphisms and evaluated for free eculizumab in plasma. We report that 10 patients (83%) present parameters suggesting persistent hemolysis, although they did not require additional transfusions. Seven of them (58%) become direct Coombs-test positive as a consequence of treatment, including all patients carrying the low-expression CR1-L allele. CH50 and sC5b-9 assays demonstrate that the persistent low-level hemolysis identified in our treated patients is not a consequence of incomplete C5 blockade, supporting that this hemolysis, as has been suggested previously, results from the extravascular removal of C3 opsonized PNH erythrocytes. We also show that continuous alternative pathway activation in eculizumab-treated individuals carrying the CR1-L allele results in abnormally decreased levels of C3 in plasma that could, potentially, increase their susceptibility to bacterial infections. Finally, we encourage a routine evaluation of free eculizumab levels and terminal pathway activity to personalize eculizumab administration.
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Subías Hidalgo
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Hector
authors.initials: H
authors.lastname: Martin Merinero
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: López
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Jaouad
authors.initials: J
authors.lastname: Anter
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Sheila Pinto
authors.initials: SP
authors.lastname: García
authors.affiliation: Servicio de Hematología, Hospital Clínico San Carlos de Madrid, Madrid, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Ataúlfo Gonzalez-Fernández
authors.affiliation: Servicio de Hematologia, Hospital Universitario Puerta de Hierro, Majadahonda, Madrid, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Forés
authors.affiliation: Unidad de Inmunología, Hospital Universitario de La Paz y Ciber de Enfermedades Raras, Madrid, Spain.
authors.forename: Margarita
authors.initials: M
authors.lastname: Lopez-Trascasa
authors.affiliation: Servicio de Hematología, Hospital Clínico San Carlos de Madrid, Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Villegas
authors.affiliation: Servicio de Hematologia, Hospital Universitario Puerta de Hierro, Majadahonda, Madrid, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Ojeda
authors.affiliation: Departamento de Medicina Celular y Molecular, Centro de Investigaciones Biologicas y Ciber de Enfermedades Raras, Madrid, Spain. Electronic address: srdecordoba@cib.csic.es.
authors.forename: Santiago
authors.initials: S
authors.lastname: Rodríguez de Córdoba
mesh_terms: D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D003167:Complement Activation / Q000187:drug effects / Q000276:immunology; D003176:Complement C3 / Q000276:immunology; D003182:Complement C5 / Q000276:immunology; D051056:Complement Inactivating Agents / Q000627:therapeutic use; D003165:Complement System Proteins / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D005838:Genotype; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000276:immunology*; D006461:Hemolysis / Q000276:immunology*; D006801:Humans; D007223:Infant; D008297:Male; D017463:Receptors, Complement 3b / Q000235:genetics / Q000378:metabolism; D016896:Treatment Outcome
chemical_list: D061067:Antibodies, Monoclonal, Humanized; C509991:CR1 protein, human; D003176:Complement C3; D003182:Complement C5; D051056:Complement Inactivating Agents; D017463:Receptors, Complement 3b; D003165:Complement System Proteins; C481642:eculizumab
keywords: Complement; Complement receptor 1; Eculizumab; PNH; extravascular hemolysis