Binding mechanisms of therapeutic antibodies to human CD20

Science. 2020 Aug 14;369(6505):793-799. doi: 10.1126/science.abb8008.


Monoclonal antibodies (mAbs) targeting human antigen CD20 (cluster of differentiation 20) constitute important immunotherapies for the treatment of B cell malignancies and autoimmune diseases. Type I and II therapeutic mAbs differ in B cell binding properties and cytotoxic effects, reflecting differential interaction mechanisms with CD20. Here we present 3.7- to 4.7-angstrom cryo-electron microscopy structures of full-length CD20 in complexes with prototypical type I rituximab and ofatumumab and type II obinutuzumab. The structures and binding thermodynamics demonstrate that upon binding to CD20, type II mAbs form terminal complexes that preclude recruitment of additional mAbs and complement components, whereas type I complexes act as molecular seeds to increase mAb local concentration for efficient complement activation. Among type I mAbs, ofatumumab complexes display optimal geometry for complement recruitment. The uncovered mechanisms should aid rational design of next-generation immunotherapies targeting CD20.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal, Humanized / chemistry*
  • Antibodies, Monoclonal, Humanized / immunology
  • Antibodies, Monoclonal, Humanized / therapeutic use
  • Antigen-Antibody Complex / chemistry*
  • Antigen-Antibody Complex / immunology
  • Antigens, CD20 / chemistry*
  • Antigens, CD20 / immunology
  • Antineoplastic Agents / chemistry*
  • Antineoplastic Agents / immunology
  • B-Lymphocytes / immunology
  • Complement Activation
  • Cryoelectron Microscopy
  • Humans
  • Immunoglobulin Fab Fragments / chemistry
  • Immunoglobulin Fab Fragments / immunology
  • Immunotherapy*
  • Lymphoma, B-Cell / therapy*
  • Protein Binding
  • Protein Conformation
  • Rituximab / chemistry*
  • Rituximab / immunology
  • Rituximab / therapeutic use


  • Antibodies, Monoclonal, Humanized
  • Antigen-Antibody Complex
  • Antigens, CD20
  • Antineoplastic Agents
  • Immunoglobulin Fab Fragments
  • Rituximab
  • ofatumumab
  • obinutuzumab