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BsAbs for Forced Protein Associations

Creative Biolabs is a global leader in the rapidly emerging market for bispecific antibodies (BsAbs) and is experienced to engineer and produce BsAbs for forced protein associations, such as KIH BsAbs.

Bivalent in composition with each arm binding to one antigen/ protein, BsAbs can be used to bring two targets together into one complex. An interesting application of BsAbs is forcing the associations of proteins. This function is very useful when two factors or molecules are required to make contacts for a certain signaling pathway.

BsAb designed for forced protein association. (Kontermann, R. E., 2015)

Figure 1. BsAb designed for forced protein association. (Kontermann, R. E., 2015)

BsAbs for Forced Protein Associations

In certain cases, contact between two or more factors is required in certain signaling pathways. BsAbs can bind two such factors and bring them together. For example, coagulation factor VIIIa brings together Factor IXa and Factor X in the coagulation cascade and triggers following signaling pathway in healthy people. In patients with the bleeding disorder hemophilia A, coagulation factor VIIIa is missing. Previous treatment supplies patients with FVIII, a factor that can effectively reduce bleeding complications. However, FVIII has a very short half-life and is poorly bioavailable. What’s worse, since FVIII gene is missing in patients, the provided FVIII factor becomes a ‘foreign’ protein and often causes immune responses. Therefore, many patients cannot take FVIII treatment. RG6013 is a KIH-common light chain IgG derivative. It binds Factor IXa and Factor X simultaneously and triggers subsequent pathways. Its Fc region ensures a long serum half-life of the drug. Therefore, RG6013 overcomes both limitations of the FVIII treatment and restores blood coagulation.

Knobs-into-holes (KIH) Technique

The combination of a common light chain with ‘knobs-into-holes’ (KIH) technique is one widely used strategy to solve the heavy chain and light chain pairing problems. This strategy utilizes KIH structure in the CH3 domain of the heavy chains, which results in the automatic correct heterodimerization of two CH3 domains of the heavy chains. CH3 domains with knobs-into-holes are generated by replacing large amino acids by small ones in one domain and introducing large ones in the other domain. In combination, by using the same light chain sequence, the light chain-heavy chain pairing produces only one type of product. The mispairing problems, which lead to a substantial number of unwanted antibody products and cause trouble for the subsequent purification of the desired BsAbs, are circumvented by this strategy.

With our top antibody engineering platforms, Creative Biolabs provides one-stop BsAb services that meet all customers’ demands. We can produce various forms of BsAbs designed for forced protein associations.


1. Kontermann, R. E.; Brinkmann, U. Bispecific antibodies. Drug discovery today. 2015, 20(7): 838-847.
2. Shatz, W.; et al. Knobs-into-holes antibody production in mammalian cell lines reveals that asymmetric afucosylation is sufficient for full antibody-dependent cellular cytotoxicity. MAbs. 2013, 5(6): 872-881.

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