ABSTRACT
Monoclonal antibodies (mAbs) are biological macromolecules with complex post-translational modifications that can be observed when assessing product variants. The N- and C-terminal heterogeneities of commercially produced antibodies have been observed and extensively studied over the past 30 years. This review summarizes the current literature on detectable antibody termini variants from cultured cells. The presence of these heterogeneities can be detected by many different analytical methods, mostly based on sequence, charge and size differences. Examples are presented that highlight terminal heterogeneities, methods of detection, and their impact on the quality of mAbs. Regulatory considerations are also discussed regarding the potential impact on product quality, safety, and efficacy.
Subject(s)
Antibodies, Monoclonal/chemistry , Biotechnology , Protein Processing, Post-Translational , Animals , Antibodies, Monoclonal/isolation & purification , Antibodies, Monoclonal/therapeutic use , Drug Storage , Glutamic Acid/metabolism , Protein Isoforms/chemistry , Protein Isoforms/isolation & purification , Protein Isoforms/therapeutic use , Pyrrolidonecarboxylic Acid/metabolismABSTRACT
Chicken anti-IL-12 monoclonal antibodies were isolated by phage display using spleen cells from a chicken immunized with human and mouse IL-12 as a source for library construction. One of the chicken monoclonal antibodies, DD2, exhibited binding to both human and mouse IL-12 in the single-chain Fv form and also after conversion to chicken-human chimeric IgG1/lambda antibody. The chicken DD2 variable regions were humanized by transferring their CDRs and several framework amino acids onto human acceptor variable regions. In the Vlambda, six chicken framework amino acids were identified to be important for the conformation of the CDR structure by computer modeling and therefore were retained in the humanized form; likewise, five chicken amino acids in the VH framework regions were retained in the humanized VH. The affinities of humanized DD2 IgG1/lambda to human and mouse IL-12 measured by competitive binding were nearly identical to those of chicken-human chimeric DD2 IgG1/lambda. This work demonstrates that humanization of chicken monoclonal antibodies assisted by computer modeling is possible, leading to a new way to generate therapeutic humanized antibodies against antigens to which the rodent immune system may fail to efficiently raise high affinity antibodies.