Fc antigen binding site: Mab²

The production of bispecific antibodies involves the addition of a second antigen-binding site in the Fab arms. Sometimes, these types of bispecific products have problems such as poor stability, immunogenicity and challenges in the manufacturing process. Hence, Mab2 simply replaces the Fc region of an existing antibody with an Fcab that binds to a second target of interest to create a full-length bispecific monoclonal antibody (Fig. 1a). It binds with the two different antigens at the same time with favorable pharmacokinetics, antibody-dependent cellular cytotoxicity, and excellent stability and ease of manufacturing.

Figure 1: A schematic illustration of the mAb2 bispecific antibody. (Adopted from: https://media.nature.com/original/magazine-assets/d43747-020-00078-4/d43747-020-00078-4.pdf)

Formats of bispecific antibodies (BsAbs)

Many formats have been developed for BsAb generation as listed in the following table.