Humanization and Affinity Maturation

Since the approval of Orthoclone Okt3, a mouse-derived monoclonal antibody drug that reduces the natural immunity of organ recipients (such as kidneys) by the US FDA in 1986, monoclonal antibody drugs have been developed for nearly 36 years. During this period, the development of monoclonal antibody drugs has been flourishing, and new technological forms have emerged one after another.

What is humanization of antibodies?

The first chimeric antibody drug is Abciximab. Chimeric antibodies are composed of mouse antibodies and human antibodies. The constant region is composed of human amino acid sequences, while the variable region responsible for binding to antigens is composed of mouse amino acid sequences. Then came the humanized antibody drugs, which further replaced the mouse-derived amino acids in the variable region of the chimeric antibodies with human-derived amino acids, so that in the end, except for the key amino acids in regions such as CDR still retaining mouse-derived amino acids, other parts were replaced with human-derived amino acids. Finally, in humanized monoclonal antibodies, the proportion of human-derived amino acid sequences reached 90%, or even more than 95%.

Why is it necessary to humanize antibodies?

The amino acid composition of murine monoclonal antibody drugs differs from that of humans, which can attract the attention of the immune system, thereby causing an immune response in the body. This leads to the production of human anti-murine antibodies (HAMA), which results in the rapid clearance of murine monoclonal antibodies in the human body, shortening the half-life, and thus limiting the clinical efficacy of murine antibodies. In a few cases, murine antibodies can cause severe allergic reactions, even leading to the death of individual patients.

Methods for humanizing antibodies

The biggest drawback of humanized monoclonal antibody technology is the lack of a universal method. Each antibody molecule needs to be humanized through individual analysis, molecular modeling, extensive modification, and trial and error.

Kyinno has independently developed an AI and structure-based fully automatic antibody humanization integrated algorithm platform. This platform integrates powerful functions such as antibody structure modeling, selection of human templates, CDR-grafting, CDR/SDR transplantation, modification site modification, patent analysis, solubility, stability, charge and half-life, immunogenicity and a series of antibody humanization and drug-related analysis and modification optimization.

The process is shown in the following figure. The degree of humanization can reach 95%-97% or even higher. At the same time, the final humanization design also removes related potential risk points, such as potential post-translational modification sites (deamination, isomerization, oxidation, glycosylation, etc.), immunogenic sites. It also includes optimization of isoelectric point and surface charge, surface hydrophilicity and hydrophobicity, solubility, stability and so on. Relying on the establishment of this platform, it avoids individual analysis, molecular modeling, extensive modification and trial and error in the process of humanization, not only improves efficiency and success rate, but also greatly shortens the entire R&D cycle of antibody drugs, reduces costs and reduces error rates.

The final humanized antibody also avoids a series of problems caused by post-translational modifications and immunogenicity that lead to poor drug properties and high risks in the later stages.