The transgenic chicken derived anti-CD20 monoclonal antibodies exhibits greater anti-cancer therapeutic potential with enhanced Fc effector functions

Modern genetic techniques, enable the use of animal bioreactor systems for the production and functional enhancement of anti-cancer antibodies. Chicken is the most efficient animal bioreactor for the production of anti-cancer antibodies because of its relatively short generation time, plentiful reproductive capacity, and daily deposition in the egg white. Although several studies have focused on the production of anti-cancer antibodies in egg white, in-depth studies of the biological activity and physiological characteristics of transgenic chicken-derived anti-cancer antibodies have not been fully carried out. Here, we report the production of an anti-cancer monoclonal antibody against the CD20 protein from egg whites of transgenic hens, and validated the bio-functional activity of the protein in B-lymphoma and B-lymphoblast cells. Quantitative analysis showed that deposition of the chickenised CD20 monoclonal antibody (cCD20 mAb) from transgenic chickens increased in successive generations and with increasing transgene copy number. Ultra-performance liquid chromatography (UPLC) tandem mass spectrometry (LC/MS/MS) analysis showed that the cCD20 mAb exhibited 14 N-glycan patterns with high-mannose, afucosylation and terminal galactosylation. The cCD20 mAb did not exhibit significantly improved Fab-binding affinity, but showed markedly enhanced Fc-related functions, including complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) compared to commercial rituximab, a chimeric mAb against CD20. Our results suggest that the transgenic chicken bioreactor is an efficient system for producing anti-cancer therapeutic antibodies with enhanced Fc effector functions.

Rational Design of Biobetters with Enhanced Stability

Biotherapeutics are the fastest growing class of pharmaceutical with a rapidly evolving market facing the rise of biosimilar and biobetter products. In contrast to a biosimilar, which is derived from the same gene sequence as the innovator product, a biobetter has enhanced properties, such as enhanced efficacy or reduced immunogenicity. Little work has been carried out so far to increase the intrinsic stability of biotherapeutics via sequence changes, even though, aggregation, the primary degradation pathway of proteins, leads to issues ranging from manufacturing failure to immunological response and to loss of therapeutic activity. Using our spatial aggregation propensity tool as a first step to a rational design approach to identify aggregation-prone regions, biobetters of rituximab have been produced with enhanced stability by introducing site-specific mutations. Significant stabilization against aggregation was achieved for rituximab with no decrease in its binding affinity to the antigen.

Comparability analysis of anti-CD20 commercial (rituximab) and RNAi-mediated fucosylated antibodies by two LC-MS approaches

In developing biosimilar or biobetter products, comparability to the reference product is required to claim similar integrity or intended purpose. In this work, an anti-CD20 monoclonal antibody developed using RNA interference to decrease core fucosylation (RNAi-mediated) was comprehensively characterized by LC-MS and compared with the commercially-available anti-CD20 rituximab (MabThera (®) ). As anticipated, < 30% core fucose was found within the RNAi-produced molecule (compared with > 90% in rituximab), and the reduction in fucose resulting in a significant improvement in FcγRΙΙΙa binding and antibody-dependent cell-mediated cytotoxicity. Two mutations, S258Y (fully mutated) and F174I/L (partially mutated), however, were detected in the production of the RNAi-mediated molecule. An alternative LC-MS approach using dimethyl labeling (i.e., 2CH 2 for rituximab and 2CD 2 for the RNAi-mediated molecule) was developed to additionally compare the two mAbs and confirm the full sequence with the two mutation sites. Furthermore, disulfide linkages were found to be the same for the two antibodies, with a small portion of unpaired cysteines in both products. Disulfides were correctly linked if the samples were prepared at low pH (i.e., enzymatic digestion by pepsin at pH 2); however, trace amounts of scrambling were found by trypsin digestion at pH 6.8, and this scrambling increased significantly at pH 8. Typical modifications, such as pyro-Glu formation at the N-terminus, K clipping at the C-terminus, oxidation at Met, and deamidation at Asn, were also detected with no significant differences between the two products. Using the LC-MS approaches for the comparability study, product integrity with critical structure information was revealed for confirmation of intended purpose (core fucosylation), identification of critical parameters (e.g., sample pH), and correction as needed (amino acid mutation).