Abstract
Bispecific antibodies (BsAb) refer to a class of biomacromolecules that are capable of binding two antigens or epitopes simultaneously. This can elicit unique biological effects that cannot be achieved with either individual antibody or two unlinked antibodies. Bispecific antibodies have been used for targeting effector cells to tumor cells, preferential targeting of cells expressing two target biomarkers over cells expressing either target biomarker individually, or to couple two molecular targets on the same cell surface to trigger unique intracellular signaling pathways. Here, we present two related methods that enable direct, rapid assembly of bispecific antibodies from any two "off-the-shelf" Immunoglobulin G (IgG) antibodies, in as little as 1 day. Both workflows can be summarized into two steps: (1) attach a small photoreactive antibody binding domain (pAbBD) fused to SpyCatcher or SpyTag (peptide-protein partners derived from the S. pyogenes fibronectin-binding protein FbaB) to each component IgG, respectively; (2) assemble the BsAb through the spontaneous isopeptide bond formation that occurs between SpyTag and SpyCatcher. These approaches enable production of BsAbs from any two IgG molecules without the need to elucidate their amino acid sequences or genetically alter their structure. Binding assays and T cell-mediated cytolysis assays were performed to validate the binding and functional properties of Trastuzumab × Cetuximab BsAb and Cetuximab × OKT3 BsAb, respectively. This approach enables rapid, low-cost production of highly homogeneous tetravalent BsAbs in a modular fashion, presenting an opportunity to quickly evaluate antibody pairs in a BsAb format for unique or synergistic functionalities.