Atacicept

Atacicept is a recombinant fusion protein designed to inhibit B cells, thereby suppressing autoimmune disease. The designer protein combines the binding site for two cytokines that regulate maturation, function, and survival of B cells - B-lymphocyte stimulator (BLyS) and A proliferation-inducing ligand (APRIL), with the constant region of immunoglobin. Atacicept blocks activation of B cells by the tumor necrosis factor receptor superfamily member 13B (more commonly known as TACI), a transmembrane receptor protein found predominantly on the surface of B cells. Like the monoclonal antibody belimumab, atacicept blocks the binding of BLyS, but it also blocks APRIL. Binding of these TACI ligands induces proliferation, activation, and longevity of B cells and thus their production of autoantibodies. Atacicept is thought to selectively impair mature B cells and plasma cells with less impact on progenitor cells and memory B cells.