title: Characterization of a rituximab variant with potent antitumor activity against rituximab-resistant B-cell lymphoma.
abstract: Despite widespread use of the anti-CD20 monoclonal antibody (mAb), rituximab, in treating B-cell lymphomas, its efficacy remains variable and often modest. A better understanding of rituximab-mediated killing mechanisms is essential to develop more effective therapeutic agents. In this study, we modulated the binding property of rituximab by introducing several point mutations in its complementarity-determining regions. The data showed that changing the binding avidity of rituximab in the range from 10(-8) to 10(-10) M could regulate its antibody-dependent cellular cytotoxicity but not affect its complement-dependent cytotoxicity and apoptosis-inducing activity in B-lymphoma cells. Contradictory to previous findings, we found that the complement-dependent cytotoxicity potency of CD20 mAb was independent of the off-rate. Despite still being a type I CD20 mAb, a rituximab triple mutant (H57DE/H102YK/L93NR), which had a similar binding avidity to a double mutant (H57DE/H102YK), was unexpectedly found to have extremely potent apoptosis-inducing activity. Moreover, this triple mutant, which was demonstrated to efficiently initiate both caspase-dependent and -independent apoptosis, exhibited potent in vivo therapeutic efficacy, even in the rituximab-resistant lymphoma model, suggesting that it might be a promising therapeutic agent for B-cell lymphomas.
authors.affiliation: International Joint Cancer Institute and 301 General Hospital Cancer Center, Second Military Medical University, Shanghai, People's Republic of China.
authors.forename: Bohua
authors.initials: B
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
authors.forename: Huaizu
authors.initials: H
authors.lastname: Guo
authors.forename: Chong
authors.initials: C
authors.lastname: Wang
authors.forename: Xunming
authors.initials: X
authors.lastname: Zhang
authors.forename: Lan
authors.initials: L
authors.lastname: Wu
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.forename: Qing
authors.initials: Q
authors.lastname: Tong
authors.forename: Weizhu
authors.initials: W
authors.lastname: Qian
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Yajun
authors.initials: Y
authors.lastname: Guo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D000915:Antibody Affinity; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D022801:Complementarity Determining Regions / Q000235:genetics; D015195:Drug Design; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D016393:Lymphoma, B-Cell / Q000188:drug therapy*; D051379:Mice; D016513:Mice, SCID; D017354:Point Mutation; D000069283:Rituximab; D023041:Xenograft Model Antitumor Assays
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D000970:Antineoplastic Agents; D022801:Complementarity Determining Regions; D000069283:Rituximab