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scFv-Fab Fragments BsAb Generation Service

scFv-Fab fragments are the class of BsAb fusing Fab and scFv. Creative Biolabs has elaborately integrated multiple platforms for providing customers expected scFv-Fab fragments BsAbs with high affinity and low immunogenicity for both academic and clinical purposes.

BsAbs are powerful tools in the development of new experimental therapies of a variety of diseases. Bispecific single-chain variable fragment (scFv)2 heterodimers have been generated via direct genetic fusion, or indirectly through fusion to helical heterodimerization domains. In order to avoid the rapid blood and whole-body clearance displayed by these small-sized molecules, methods have been developed to form intermediate- and larger-sized recombinant BsAb. Potent heterodimerization of complete heavy chains was achieved through engineering complementarity into the domain interfaces of two CH3 molecules. So as to get optimal results, a disulfide bridge need to be introduced into the molecule to stabilize the heterodimer. Besides, single Ab domains (e.g., CL or CH3) have been used for homodimerization, forming bivalent minibodies. These intermediate-sized molecules refrained from clearance in the kidney, and they still have a more efficient tissue penetration than common Abs, which allows them better suited for in vivo therapeutic application.

Structure of scFv-Fab fragments bispecific BsAbs.

Figure 1. Structure of scFv-Fab fragments bispecific BsAbs.

scFv-Fab BsAb Fragments

One of the major problems affecting BsAb production is the unwanted mono-specific homodimers. To overcome this issue, scFv-Fab fragments BsAbs are developed by taking advantage of the naturally occurring pairing mechanism between Fab regions (hinge region), which is similar with that of triple body utilizing the pairing within Fab. This classes of BsAb fragment mainly include F(ab’)2-scFv2 and Fab-scFv-Fc. F(ab’)2-scFv2 can be regarded as that the fc domain of conventional IgGs are replaced by scFv. So the expression cassette of F(ab’)2-scFv2 is also similar to IgG, variant HC and LC. While in the format of Fab-scFv-Fc, Fab-Fc fragment and scFv-Fc fragment with distinct specificity can also be paired through the interaction between hinge and Fc domains. Moreover, in order to facilitate the correct pairing of the two different heavy chains, the Fc engineering with KIH (knobs-in-holes) is preferred.

With our well-established BsAb fragment generation platform, the experienced scientists here at Creative Biolabs are dedicated to helping you develop unique BsAbs. We also provide other various services regarding BsAbs development. Please feel free to contact us for more information and a detailed quote.


1. Schoonjans, R.; et al. Fab chains as an efficient heterodimerization scaffold for the production of recombinant bispecific and trispecific antibody derivatives. The Journal of Immunology. 2000, 165(12): 7050-7057.
2. Mertens, N. Tribodies: fab–scfv fusion proteins as a platform to create multifunctional pharmaceuticals. Bispecific Antibodies. Springer Berlin Heidelberg. 2011: 135-149.

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