Paul Smyth, MD, Contributing Writer, MedPage Today Three drugs that inhibit the immunoglobulin G (IgG) neonatal fragment crystallizable receptor (FcRn) were approved to treat generalized myasthenia gravis (MG) in recent years: efgartigimod (Vyvgart), rozanolixizumab (Rystiggo), and nipocalimab (Imaavy).