Efgartigimod is a first-in-class investigational antibody fragment being evaluated for the treatment of patients with severe autoimmune diseases associated with high levels of pathogenic immunoglobulin G, or IgG, where a severe unmet medical need exists. Efgartigimod is thought to degrade circulating disease-causing autoimmune antibodies and is being investigated in large and orphan indications like myasthenia gravis (MG), immune thrombocytopenia (ITP) and skin blistering diseases and likely has wider therapeutic potential.

Clinical trials

  • Ongoing Phase 3 ADAPT clinical trial in myasthenia gravis, recruiting up to 150 patients

  • Phase 2 proof-of-concept trial of intravenous (IV) in primary ITP:
    • Safety and tolerability consistent with efgartigimod clinical trials to-date
    • Platelet count improvements seen across doses and ITP patient classifications, correlating with reduction in IgG levels
    • Separation from placebo at increasing response thresholds, with response rates of 46% and 58% in primary trial and first dosing of open-label extension study, respectively
  • Positive Ph2 topline data in MG:
    • Safety profile consistent with Phase 1 data
    • Efgartigimod treatment resulted in a significant redution in IgG over placebo during the entire duration of the study
    • 75% of patients achieved clinically meaningful improvement as measured by the Myasthenia Gravis-specific Activities of Daily Living scale (MG-ADL) for at least 6 consecutive weeks versus 25% of patients on placebo
  • Phase 2 clinical trial in PV; recruitment is ongoing
  • Phase 1 safety trial in healthy volunteers completed
  • Data set from Phase 1 single ascending dose (SAD) and multiple ascending dose (MAD) studies showed favorable safety profile and specific IgG reduction of up to 85 % with a long duration of effect, with repeated dosing of the drug

Mode of action

  • Efgartigimod binds FcRn and is believed to block IgG recycling (including disease-causing autoantibodies) and increase IgG clearance

  • Antibody fragment designed using ABDEG™ technology

 Nat Biotechnol 2005, Vacaro et al.


  • Neonatal Fc receptor (FcRn):
    • Recycling receptor for IgG’s
    • Ability to rescue IgG from destruction
    • Responsible for maintenance of high concentration of IgG (including autoantibodies) in circulation
 Nature Review 2007, Roopenian and Akilesh

Efgartigimod-related publications

 ARGX-113 poster - MG Conference NY  Intensive plasma exchange therapy..., Blanchette et al., Transfusion, 1984  Familial hypercatabolic hypoproteinemia caused..., Wani et al., PNAS, 2006  Infusion of Fc gamma fragments for treatment..., Debré et al., Lancet, 1993  Transcytosis and catabolism of antibody. Chetie and Ward, Immunol Res., 2002  Engineering the Fc region of..., Vaccaro et al., Nature Biotechnol., 2005  Complete FcRn dependence for intravenous Ig..., Li et al., J Clin Invest., 2005  Divergent activities of an engineered antibody..., Vaccaro et al., PNAS, 2006  Amelioration of experimental autoimmune..., Liu et al., J Immunol., 2007  Pharmacokinetic/pharmacodynamic modeling ..., Deng and Balthasar, Interscience, 2007  FcRn: the neonatal Fc receptor comes..., Roopenian et al., Nat Rev Immunol., 2007  Antibodies in myasthenia gravis, Eymard, Rev Neurol., 2009  The neonatal Fc receptor as therapeutic..., Liu et al., Ther. Apher. Dial., 2010  The neonatal Fc receptor as therapeutic target..., Sesarman et al., Cell Mol. Life Sci., 2010  History of outcome measures for myasthenia gravis, Burns, Muscle Nerve, 2010  Comparison of IVIg and PLEX in patients with MG, Barth et al., Neurology, 2011  Neonatal Fc receptor blockade by Fc engineering..., Patel et al., J Immunol., 2001  Autoantibody depletion ameliorates disease..., Challa et al., MAbs, 2013  A randomized, double-blind, placebo-controlled phase II..., Howard et al., Muscle Nerve, 2013  The multiple facets of FcRn in immunity, Stappleton et al., Immunol Rev., 2015  Fc Engineering of Human IgG1 for Altered Binding..., Greveys et al., J Immunol., 2015  Effect of therapeutic plasma exchange..., Guptill et al., Autoimmunity, 2016  Myasthenia Gravis, Gilhus, NEJM, 2016


  • Myasthenia Gravis (MG)

    Myasthenia Gravis is an auto-immune disease that leads to fluctuating muscle weakness and fatigue.  

    MG is an autoimmune disorder associated with muscle weakness that is triggered by IgG auto-antibodies. These antibodies attack critical signaling proteins at the junction between nerve and muscle cells, thereby impairing their communication signals. In MG these auto-antibodies either bind and occupy or cross-link and internalize the receptor on the muscle cells, thereby preventing the binding of acetylcholine, the signal sent by the nerve cell. In addition, these auto-antibodies can cause destruction of the neuromuscular junction by recruiting complement, a potent cell-destroying mechanism of the human immune system.

    The muscle weakness associated with MG usually presents initially in ocular muscles and can then spread into a generalized form affecting multiple muscles. MG initially causes droopy eyelids and blurred or double vision due to partial paralysis of eye movements. As MG becomes generalized it affects muscles in the neck and jaw, causing problems in speaking, chewing and swallowing. MG can also cause weakness in skeletal muscles leading to problems in limb function. In the most severe cases, respiratory function can be weakened to the point where it becomes life-threatening. These respiratory crises occur at least once in the lives of approximately 15% to 20% of MG patients. The U.S. prevalence of MG is estimated at approximately 20 cases per 100,000. Currently, there are an estimated 64,000 MG patients in the United States, of which an estimated 55,000 patients are
    suffering from generalized MG. We believe that the prevalence in Europe is at a similar level. Our initial focus is on generalized MG patients whose disease is not well-controlled with corticosteroids and immunosuppressants, which we believe represents a majority of generalized MG patients.

  • Immune Thrombocytopenia (ITP)

    Immune thrombocytopenia is an autoimmune disease affecting platelets. 

    ITP is a bleeding disease caused by an autoimmune reaction in which a patient develops antibodies that attack and destroy their own platelets, which are blood cells that help blood to clot, or their own platelet-forming cells. ITP, which develops for no known reason, is differentiated from secondary immune thrombocytopeania, which is associated with other illnesses, such as infections
    or autoimmune diseases, or which occurs after transfusion or taking other drugs, such as cancer drugs. Platelet deficiency, or thrombocytopenia, can cause bleeding in tissues, bruising and slow blood clotting after injury. ITP affects approximately 72,000 patients in the United States.

  • Pemphigus Vulgaris (PV)

    Pemphigus vulgaris is a rare autoimmune disease that causes painful blistering on the skin and mucous membranes.

    Pemphigus vulgaris is a rare autoimmune disease that causes painful blistering on the skin and mucous membranes.

    Pemphigus vulgaris is the most common type of a group of autoimmune disorders called pemphigus. Each type of pemphigus is characterized by the location where the blisters form.

    This disease usually starts with blisters in the mouth and then on the skin. The blisters sometimes affect the membranes of the genitals.

    Pemphigus vulgaris can be dangerous. Treatment is essential, and typically it involves the use of corticosteroids to suppress the immune system. The condition can cause serious complications it isn’t treated. Some of these complications can be fatal.