In 2018, the global biopharmaceutical market reached a scale of $261.8 billion, with monoclonal antibody drugs accounting for $119.3 billion. The global monoclonal antibody drug market grew from $80.1 billion in 2014 to $119.3 billion in 2018, with a compound annual growth rate of 10.5%. It is projected to maintain a growth rate of 11.7% in the future. There are nearly 300 domestic companies involved in the field of antibody development in China, making the competition in antibody applications increasingly fierce.

Apart from competition in terms of funding, talent, CMC (Chemistry, Manufacturing, and Controls), and clinical resources, achieving differentiation in antibody design is the fundamental basis for future product market competition. In addition to selecting antibodies that target different antigen epitopes, engineering modifications of the Fc region can significantly alter the biological effects and half-life of antibodies. This is an important approach for achieving differentiation in antibody competition.

Fc receptors (FcR) are receptors that specifically bind to the Fc portion of immunoglobulins (Ig). The most commonly used receptors for detecting and binding antibodies are FcRn and FcγR. Unlike other types of Fc receptors, FcRn has a structure similar to MHC class I molecules. Mature FcRn is a heterodimeric molecule composed of two subunits, p51 and p14 (β2-microglobulin), forming a structure resembling MHC class I molecules.

FcRn is present in various tissues and organs, including vascular endothelial cells, monocytes/macrophages, dendritic cells, and other antigen-presenting cells (APCs) derived from the myeloid lineage. It plays a crucial role not only in the transfer of IgG from mother to fetus but also in determining the half-life of antibodies through its interaction with antibodies.

The FcγR family can be broadly divided into three classes: FcγRI, FcγRII, and FcγRIII. FcγRI has a high affinity for IgG (10^9 M-1) and is mainly expressed on monocytes and macrophages. FcγRII and FcγRIII have a lower affinity for IgG (10^6 M-1) and are more widely distributed. FcγRII is further classified into three types (FcγRIIA, FcγRIIB, and FcγRIIC) based on the structure of their cytoplasmic region. They are found in B cells, macrophages, polymorphonuclear cells, platelets, and monocytes. FcγRIII is found in neutrophils, natural killer cells, macrophages, and activated monocytes.

The binding of FcγRs to antibodies can activate immune cells and lead to internalization, phagocytosis, antibody-dependent cell-mediated cytotoxicity (ADCC), and other functions.

Due to the binding of antibodies to Fc receptors, not only the half-life of the antibody drug can be affected, but also the induction of corresponding immune response functions in the body, such as antibody-dependent cellular cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and phagocytosis of target antigens after processing. These factors are crucial for evaluating the function, efficacy, and safety of antibody drugs. Therefore, high-quality Fc receptors are essential for obtaining ideal antibodies. BetaLifeScience provides a range of Fc receptor proteins that have been validated by surface plasmon resonance (SPR) and high-performance liquid chromatography (HPLC), offering high-performance tools for your antibody drug development.

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