Frontier of therapeutic antibody discovery: The challenges and how to face them

Abstract

Therapeutic monoclonal antibodies have become an important class of modern medicines. The established technologies for therapeutic antibody discovery such as humanization of mouse antibodies, phage display of human antibody libraries and transgenic animals harboring human IgG genes have been practiced successfully so far, and many incremental improvements are being made constantly. These methodologies are responsible for currently marketed therapeutic antibodies and for the biopharma industry pipeline which are concentrated on only a few dozen targets. A key challenge for wider application of biotherapeutic approaches is the paucity of truly validated targets for biotherapeutic intervention. The efforts to expand the target space include taking the pathway approach to study the disease correlation. Since many new targets are multi-spanning and multimeric membrane proteins there is a need to develop more effective methods to generate antibodies against these difficult targets. The pharmaceutical properties of therapeutic antibodies are an active area for study concentrating on biophysical characteristics such as thermal stability and aggregation propensity. The immunogenicity of biotherapeutics in humans is a very complex issue and there are no truly predictive animal models to rely on. The in silico and T-cell response approaches identify the potential for immunogenicity; however, one needs contingency plans for emergence of anti-product antibody response for clinical trials.

Beyond CDR-grafting: Structure-guided humanization of framework and CDR regions of an anti-myostatin antibody

“…2,3,15 Comparing the CDR grafted RK35 VH1.0/VL1.0 with the clones that had the least amount of murine content with retained activity by in vitro analysis (RK35 VL 1.4 and RK35 VH 1.5), we were able to remove 11 of 28 non-germline residues. To further demonstrate the potential decrease in immunogenicity risk, we used the Lazar et al method, which quantifies the level of potential MHC/T-cell epitopes in an antibody sequence, to determine the "humanness" of the antibody sequence.…”

“…[1][2][3] Antibodies offer specificity to antigens, as well as long serum half-life and effector functions, which are both mediated by specific sites on the constant domain. 4 Despite their obvious benefits, one major liability has been the tendency for many non-human-derived antibodies, e.g., from mouse or rat, to show a significant immunogenic response.…”

“…5,6 Moreover, it is believed that the higher the identity to natural human B cell antibodies, the lower the risk for HAMA response in the clinic. 2,3 Given the apparent link between HAMA and non-human sequence content, one popular method to address this immunogenicity risk is to reduce the murine content by humanizing the mouse antibody through complementaritydetermining region (CDR) grafting onto a human acceptor germline framework. This method leaves only the CDRs with xenogeneic residues.…”

“…[7][8][9][10] Despite this, the human anti-human antibody (HAHA) responses can still be problematic when treating with humanized antibodies. 2,[10][11][12][13][14] There is still murine content in the CDR and the HAHA response is usually associated with epitopes that at least partially contain CDR residues. 15 Therefore, to further reduce the potential risk ofof the residues within the CDRs are essential for the antibody to bind to the antigen.…”

Antibody humanization by structure-based computational protein design

“…19,20 While fully human antibody development is leading to an increasing number of approved and promising clinical candidates, the majority of FDA approved antibodies are humanized murine antibodies, 21,22 and humanization is still widely performed due to its relative maturity and low cost. 23 Antibody humanization pursues the complementary goals of increasing acceptability to the immune system while maintaining stability, specificity, and affinity. In general, humanization relies on the fact that the human immune system is relatively tolerant of human antibodies, 24 and that antibodies of any given isotype have similar modular structure and sequence-structure-function relationships.…”