B201
Generation of a fully human anti-CD20 antibody with improved effector function, through the combined use of Xenomouse and ribosome display technologies
Ross Stewart1, George Thom1, John Lund1, Michaela Levens1, Gulin Guler-Gane1, Sarahya Raja2, Shenghua Wen2, Christophe Queva2, Naomi Laing2, Anne Van Abbema2, Ping Wang4, Carlos Chavez4, Larry L Green4, Xiaoadong Yang4, Mohammad Tabrizi3, Gadi Gazit-Bornstein2, David Blakey1, Carl Webster1
1MedImmune, Cambridge, UK, 2Astrazeneca, Waltham, MA, USA, 3MedImmune, Hayward, CA, USA, 4Amgen, Fremont, CA, USA
Background
The efficacy of Rituximab in the treatment of non-hodgkin’s lymphoma has made it a mainstay of treatment for this group of diseases. Despite this success, resistance and failure to respond still occurs in certain disease settings, creating a demand for next generation anti-CD20 monoclonal antibodies with enhanced efficacy.
Method
Xenomouse technology was used to generate a fully human IgG1 specific for CD20, which was selected for its improved ability, relative to Rituximab, to induce apoptosis in B cell lymphoma lines and to elicit ADCC. Ribosome display was used to display and evolve dimeric human IgG1 Fc regions, which were then screened using a suite of biochemical and cell biological assays for enhanced effector function triggering.
Results
Screening of Xenomouse antibodies identified mAb 1.5.3, which demonstrated increased potency in vitro and increased efficacy in in vivo xenograft models, relative to Rituximab. Engineering of the human Fc domain by ribosome display identified a single point mutation at position 243 that resulted in significant increases in ADCC in vitro. Combination of the 243L mutation with the mAb 1.5.3 variable domain was additive for increases in ADCC in vitro.
Conclusion
Alternative antibody generation, selection and engineering methods were combined in order to generate a monoclonal antibody with superior activity in ADCC in vitro relative to Rituximab, and with improved in vivo efficacy.
