title: The autophilic anti-CD20 antibody DXL625 displays enhanced potency due to lipid raft-dependent induction of apoptosis.
abstract: Despite widespread use of anti-CD20 antibodies as therapeutic agents for oncologic and autoimmune indications, precise descriptions of killing mechanisms remain incomplete. Complement-dependent cytolysis and antibody-dependent cell-mediated cytotoxicity are indicated as modes of target cell depletion; however, the importance of apoptosis induction is controversial. Studies showing that the therapeutic anti-CD20 antibody rituximab (Rituxan) mediates apoptosis of tumor cell targets in vitro after cross-linking by anti-Fc reagents suggest that enhancement strategies applied to Fc-independent activities for anti-CD20 antibodies could improve therapeutic efficacy. An anti-CD20 antibody designated DXL625, with autophilic properties such as increased binding avidity, is shown here to independently induce caspase-mediated apoptosis of an established B-cell lymphoma line in vitro. Depletion of membrane cholesterol or chelation of extracellular calcium abrogated the pro-apoptotic activity of DXL625, indicating that intact lipid rafts and calcium are required for this activity. The Fc-mediated complement-dependent and antibody-dependent cellular killing mechanisms are maintained by DXL625 despite conjugation of the parental Rituxan antibody to the autophilic DXL peptide sequence. This study shows a strategy for improving anti-CD20 immunotherapy by endowing therapeutic antibodies with self-interacting properties.
authors.affiliation: InNexus Biotechnology Inc, Scottsdale, Arizona, USA.
authors.forename: Marc G
authors.initials: MG
authors.lastname: Bingaman
authors.forename: Gargi D
authors.initials: GD
authors.lastname: Basu
authors.forename: Tiana C
authors.initials: TC
authors.lastname: Golding
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Chong
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lassen
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Kindt
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Lipinski
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20 / Q000276:immunology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D021962:Membrane Microdomains / Q000187:drug effects*; D000069283:Rituximab
chemical_list: D000911:Antibodies, Monoclonal; D058846:Antibodies, Monoclonal, Murine-Derived; D018951:Antigens, CD20; D000970:Antineoplastic Agents; D000069283:Rituximab; D002118:Calcium