Nipocalimab (also known as M281) is a fully human, anti-neonatal Fc receptor (FcRn) monoclonal antibody of the IgG1 isotype. It is designed to bind with high affinity to FcRn and block its interaction with IgG, thereby accelerating the catabolism of endogenous pathogenic IgG antibodies. By lowering circulating IgG levels, including autoantibodies and alloantibodies, it aims to treat autoimmune and alloimmune diseases driven by pathogenic IgG. It is being developed for a range of conditions, including warm autoimmune hemolytic anemia (wAIHA), fetal and neonatal alloimmune thrombocytopenia (FNAIT), myasthenia gravis (MG), and other IgG-mediated disorders.