Afucosylated antibodies are characterized by the absence of fucose sugar residues on their Fc (fragment crystallizable) region. This modification has major implications for the antibody’s functionality, particularly in enhancing antibody-dependent cellular cytotoxicity (ADCC).
The primary mechanism of action of afucosylated antibodies is through enhanced ADCC. ADCC is a critical immune response where immune cells, such as natural killer (NK) cells, recognize and lyse target cells coated with antibodies. The effectiveness of ADCC largely depends on the interaction between the Fc region of the antibody and the Fcγ receptor IIIa (FcγRIIIa) on NK cells. Afucosylated antibodies exhibit increased binding affinity to FcγRIIIa due to the absence of core fucose residues, which otherwise sterically hinder this interaction in fucosylated antibodies.
Several studies have demonstrated the enhanced binding affinity of afucosylated antibodies. For instance, Shields et al. (2002) showed that removing the fucose from the Fc region increased binding affinity to FcγRIIIa by up to 50-fold, leading to significantly improved ADCC activity. This stronger binding likely leads to a more stable interaction and cross-linking between the Fc region and FcγRIIIa, directly influencing NK cell activation and subsequent target cell lysis.1
Additionally, the structural basis for this improved interaction has been characterized using crystallography. Ferrara et al. (2011) provided a detailed structural analysis, revealing that the absence of fucose alters the conformation of the Fc region, facilitating closer and more stable interactions with FcγRIIIa.2 This structural adaptation is crucial for the superior therapeutic efficacy observed in afucosylated antibodies.
Therapeutic Applications
The enhanced ADCC activity has therapeutic implications, particularly in oncology and autoimmune diseases. Several therapeutic antibodies have been developed and are currently in clinical use or undergoing clinical trials. One notable example is obinutuzumab (GA101), an afucosylated anti-CD20 monoclonal antibody used in the treatment of B-cell malignancies such as chronic lymphocytic leukemia (CLL) and follicular lymphoma. Obinutuzumab has demonstrated superior efficacy compared to rituximab, a fucosylated anti-CD20 antibody, due to its enhanced ADCC activity. A pivotal phase III study reported significantly improved progression-free survival in patients treated with obinutuzumab compared to those receiving rituximab.3,4
Another promising application is in the treatment of autoimmune diseases. For example, inebilizumab (MEDI-551) an afucosylated anti-CD19 antibody has shown potential in treating patients with relapsing forms of multiple sclerosis. It is a humanized IgG1κ monoclonal antibody which binds to and depletes CD19+ B cells. A Phase 1 study in 2017 showed inebilizumab had an acceptable safety profile with a trend in reductions in new/newly enlarging and gadolinium-enhancing lesions.5
Furthermore, advances in glycoengineering have enabled the production of afucosylated antibodies with tailored glycosylation profiles to maximize their therapeutic potential. Techniques such as glycosylation pathway engineering in CHO (Chinese hamster ovary) cells have been instrumental in this regard, ensuring consistent and high-yield production of afucosylated antibodies.6
At Biointron, our afucosylated antibody expression platform relies on our fucose-free host cell CHOK1BN-Fut8KO. The knocked-out Fut8 cell line is applied in producing afucosylated antibodies. Fut8 is an enzyme that catalyzes the formation of α-1,6 fucosyl glycosidic bonds, and thus the addition of fucose to asparagine-linked N-acetylglucosamine moieties. Contact us to learn more at info@biointron.com.
- Shields, R. L., Lai, J., Keck, R., O’Connell, L. Y., Hong, K., Meng, Y. G., … & Presta, L. G. (2002). Lack of fucose on human IgG1 N-linked oligosaccharide improves binding to human FcγRIII and antibody-dependent cellular toxicity. Journal of Biological Chemistry, 277(30), 26733-26740.
- Ferrara, C., Grau, S., Jäger, C., Sondermann, P., Brünker, P., Waldhauer, I., … & Umaña, P. (2011). Unique carbohydrate–carbohydrate interactions are required for high affinity binding between FcγRIII and antibodies lacking core fucose. Proceedings of the National Academy of Sciences, 108(31), 12669-12674.
- Alduaij, W., Ivanov, A., Honeychurch, J., Cheadle, E. J., Potluri, S., Lim, S. H., … & Cragg, M. S. (2011). Novel type II anti-CD20 monoclonal antibody (GA101) evokes homotypic adhesion and actin-dependent, lysosome-mediated cell death in B-cell malignancies. Blood, 117(17), 4519-4529.
- Townsend, W., Hiddemann, W., Buske, C., Cartron, G., Cunningham, D., Dyer, J. S., Gribben, J. G., Phillips, E. H., Dreyling, M., Seymour, J. F., Grigg, A., Trotman, J., Lin, Y., Hong, N., Kingbiel, D., Nielsen, T. G., Knapp, A., Herold, M., & Marcus, R. (2023). Obinutuzumab Versus Rituximab Immunochemotherapy in Previously Untreated iNHL: Final Results From the GALLIUM Study. HemaSphere, 7(7). https://doi.org/10.1097/HS9.0000000000000919
- Agius, M. A., Klodowska-Duda, G., Maciejowski, M., Potemkowski, A., Li, J., Patra, K., Wesley, J., Madani, S., Barron, G., Katz, E., & Flor, A. (2017). Safety and tolerability of inebilizumab (MEDI-551), an anti-CD19 monoclonal antibody, in patients with relapsing forms of multiple sclerosis: Results from a phase 1 randomised, placebo-controlled, escalating intravenous and subcutaneous dose study. Multiple Sclerosis Journal. https://doi.org/10.1177/1352458517740641
- Yang, Z., Wang, S., Halim, A., Schulz, M. A., Frodin, M., Rahman, S. H., B, M., Behrens, C., Kristensen, C., Vakhrushev, S. Y., Bennett, E. P., Wandall, H. H., & Clausen, H. (2015). Engineered CHO cells for production of diverse, homogeneous glycoproteins. Nature Biotechnology, 33(8), 842-844. https://doi.org/10.1038/nbt.3280