治療用抗体の製造方法：抗体工学

The field of antibody engineering has made significant strides in creating molecules that are increasingly effective and safe for clinical use. The engineering of therapeutic antibodies involves several sophisticated techniques aimed at producing antibodies that are not only highly specific to their target antigens but also compatible with the human immune system to minimize the risk of adverse reactions.

Techniques to Create Antibodies

There are three primary types of engineered antibodies used in therapeutics:

1. Chimeric Antibodies: These are produced by fusing the variable region (Fab) of a mouse antibody (binding to the target antigen) with the constant region (Fc) of a human antibody. This design helps reduce the immune response against the antibody compared to fully mouse antibodies, but some individuals might still show reactions. Examples of therapeutics include Erbitux (cetuximab) for colorectal cancer and Rituxan (rituximab) for certain autoimmune diseases and types of cancer. 

2. Humanized Antibodies: To further decrease immunogenicity, humanized antibodies are created by grafting only the antigen-binding sites (complementarity-determining regions, or CDRs) of a mouse antibody onto a human antibody framework. This approach retains the specificity of the mouse antibody while greatly increasing its compatibility with the human immune system. The extent of humanization influences their immunogenicity level, with more humanized versions offering lower risk. Therapeutics include Herceptin (trastuzumab) for breast cancer, and Humira (adalimumab) for rheumatoid arthritis. 

3. Fully Human Antibodies: Developed using advanced genetic engineering techniques, fully human antibodies offer the lowest risk of immunogenicity as they are entirely derived from human sequences. Examples are Darzalex (daratumumab) for multiple myeloma and Hemlibra (emicizumab) for hemophilia A.¹

Genetic Engineering in Antibody Development

Genetic engineering plays a pivotal role in discovering and optimizing antibody candidates. Techniques such as phage display, transgenic mice, and single B-cell cloning are instrumental in this process. Additionally, newer methods like directed evolution and computational antibody design are emerging, further enhancing the capabilities of antibody engineering.²

• Phage display: This technique displays diverse antibody sequences on the surface of bacteriophages. Researchers can then "pan" these libraries against specific antigens, selecting antibody candidates with desired binding properties. 

• Transgenic mice: Genetically modified mice with human antibody genes create diverse human-like antibodies. B-cells from these mice can be screened for antigen-specific antibodies of interest. 

• Single B-cell cloning: Identifying and isolating individual B-cells producing desirable antibodies allows researchers to clone and express the exact antibody sequences for further development. 

• Directed evolution: Mimicking natural selection in the lab, this technique introduces random mutations into antibody genes and selects beneficial variants with improved properties like higher affinity or lower immunogenicity. 

• Computational design: Powerful algorithms predict and design antibody sequences with desired characteristics, accelerating the optimization process. 

Biointron can help in your therapeutic antibody optimization. We provide services for Affinity Maturation and Antibody Humanization, in addition to High-throughput Recombinant Antibody Production. Learn more here: https://www.biointron.com/services/.

References:

1. Harding, F. A., Stickler, M. M., Razo, J., & DuBridge, R. B. (2010). The immunogenicity of humanized and fully human antibodies: Residual immunogenicity resides in the CDR regions. MAbs, 2(3), 256-265. https://doi.org/10.4161/mabs.2.3.11641

2. Frenzel, A., Schirrmann, T., & Hust, M. (2016). Phage display-derived human antibodies in clinical development and therapy. MAbs, 8(7), 1177-1194. https://doi.org/10.1080/19420862.2016.1212149