title: Effect of anti-CD20 monoclonal antibody, Rituxan, on cynomolgus monkey and human B cells in a whole blood matrix.
abstract: BACKGROUND
  Cynomolgus monkeys are widely used animal models in biomedical research. The differences between cynomolgus monkey and human B cells are not completely understood. However, these differences are of crucial importance for interpretation of data from studies on new therapeutic agents aimed at B-cell depletion, such as anti-CD20 monoclonal antibodies.
  
  
  METHODS
  Multicolor fluorescence-activated cell sorting analysis of peripheral blood B cells was performed on samples treated ex vivo with the anti-CD20 therapeutic monoclonal antibody, Rituxan, in a whole blood matrix.
  
  
  RESULTS
  In contrast to humans, cynomolgus monkeys had two distinct B-cell subsets, CD20highCD40lowCD21- and CD20lowCD40highCD21+. These B-cell subsets had a 2.5-fold difference in the EC50 for Rituxan binding and differed significantly in their in vitro susceptibility to Rituxan depletion. Human B cells were similar to the CD20lowCD40highCD21+ cynomolgus monkey B cells with regard to their EC50 for Rituxan and response to Rituxan in a whole blood matrix assay. CD21 was upregulated, whereas CD40 was downregulated at incubation with Rituxan in the CD20lowCD40highCD21+ monkey and human B cells in a concentration-dependent manner.
  
  
  CONCLUSIONS
  These findings have direct implications for in vivo studies of therapeutic agents that target B cells in cynomolgus monkeys and for extrapolation of the results to humans. In addition, our data are consistent with the model in which CD20, CD21, and CD40 exist in a supramolecular complex that is affected by anti-CD20 monoclonal antibodies.
authors.affiliation: Bioanalytical Research and Development Department, Genentech, Inc., South San Francisco, California 94080, USA. yulia@gene.com
authors.forename: Yulia
authors.initials: Y
authors.lastname: Vugmeyster
authors.forename: Kathy
authors.initials: K
authors.lastname: Howell
authors.forename: Anahid
authors.initials: A
authors.lastname: Bakshl
authors.forename: Clarissa
authors.initials: C
authors.lastname: Flores
authors.forename: Eleanor
authors.initials: E
authors.lastname: Canova-Davis
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology* / Q000378:metabolism; D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology*; D016175:B-Lymphocyte Subsets / Q000187:drug effects / Q000378:metabolism; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D019013:CD40 Antigens / Q000276:immunology / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D008212:Lymphocyte Depletion; D008252:Macaca fascicularis / Q000502:physiology*; D023421:Models, Animal; D017464:Receptors, Complement 3d / Q000276:immunology / Q000378:metabolism; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D019013:CD40 Antigens; D017464:Receptors, Complement 3d; D000069283:Rituximab