Overview of Dual-affinity Aetargeting

Background of Dual-affinity Retargeting

Bispecific antibodies (BsAbs) are artificial antibodies that can simultaneously bind to two different antigens or two different epitopes of one antigen. BsAbs do not exist under natural conditions, but are prepared by cell fusion or recombinant DNA technology. Because of their specificity and dual functionality, they have become a hot topic in antibody engineering and have broad application prospects in tumor immunotherapy and autoimmune diseases.Dual-affinity retargeting is a novel bispecific antibody platform technology developed by MacroGenics. dual-affinity retargeting is a heterodimeric antibody composed of two peptide chains, each containing an scFv fragment that recognizes two different antigens. Dual-affinity retargeting enhances stability and activity through inter-chain interactions and disulfide bonds. dual-affinity retargeting has the advantages of high efficiency, high affinity, low immunogenicity and so on, and shows good therapeutic potential in tumor, infection, autoimmune and other fields.

Structure Features of Dual-affinity retargeting

Dual-affinity retargeting is a heterodimeric antibody composed of two peptide chains, each containing an scFv (single-chain variable fragment) segment that recognizes two different antigens. ScFv is a single-chain antibody fragment composed of V_H (heavy chain variable region) and V_L (light chain variable region) connected by a linker peptide, which has a small molecular weight and high penetration. Dual-affinity retargeting enhances stability and activity through inter-chain interactions and disulfide bonds, and can achieve efficient cell bridging without an Fc region.

Fig.1 Schematic diagrams of dual-affinity retargeting molecule (dual-affinity retargeting). (Acheampong DO, 2019)

Generation Methods of Dual-affinity retargeting

The gene engineering preparation method of dual-affinity retargeting mainly includes the following steps: First, select the appropriate antibody variable region sequence according to the desired target, and then use linker to connect a VH and VL sequence of one antibody variable region with a VL and VH sequence of another antibody variable region to form scFv. Second, clone the two scFv fragments into expression vectors separately, and add cysteine coding sequences at the C-terminus. Finally, transfect the expression vectors into mammalian cells, use the intracellular environment to promote the formation of bispecific fragments, and purify the dual-affinity retargeting product by protein A/G affinity chromatography and other methods.

Clinic Status of Dual-affinity retargeting

There is only one so far, namely Emicizumab, which is a dual-affinity retargeting drug for patients with hemophilia A. It can bind to factor IX and factor X simultaneously, mimicking the function of the missing factor VIII and promoting blood coagulation. Emicizumab was approved by the FDA in November 2017 for the prevention or reduction of bleeding episodes in patients with hemophilia A. Emicizumab has also been approved by the European Union, Japan, Canada and other countries or regions for patients with moderate to severe hemophilia A, including those with or without antibody inhibitors.

There are several, mainly for tumor immunotherapy. They can bind to the target on the surface of tumor cells and the activation receptor on the surface of effector cells simultaneously, inducing tumor cell lysis.

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