People with myasthenia gravis (MG) may soon have an important new treatment option

If approved, efgartigimod may be effective for the ~20,000 people with MG who do not respond to conventional treatment options

November 22, 2021

Drug name:      efgartigimod
Manufacturer: argenx
Condition:       generalized myasthenia gravis

Condition overview

Myasthenia gravis (MG) is a chronic autoimmune, neuromuscular disease characterized by weakness in the skeletal muscles that worsens after activity.  The two main types of MG are ocular (affecting muscles of eyes and eyelids) and generalized. Generalized MG (gMG) affects muscles throughout the body resulting in muscle weakness that worsens with repeated use and fatigue, creating difficulties with facial expression, speech, swallowing and mobility.

There are approximately 65,000 people living with MG in the United States. About 85% of people with MG progress to gMG within 18 months. Of those, around 20,000 with gMG have an inadequate response to conventional treatments (refractory/severe gMG).

The disease occurs when the body’s immune system breaks down connections between nerve cells and muscles, which causes muscle weakness and fatigue.1 In a healthy body, nerve cell endings release acetylcholine, which binds to acetylcholine receptors found on the surface of muscle cells, causing them to contract. In people with MG, antibodies damage or block acetylcholine receptors. With fewer receptors available, muscles cannot contract properly and become weaker.

Current treatments

There is currently no cure for gMG, but treatments are available that can help control and alleviate its symptoms.

Initial therapy for mild to moderate gMG involves anticholinesterases, e.g., pyridostigmine. This can increase the levels of acetylcholine moving between nerves and muscles. It doesn’t repair the damage, but it can help control symptoms.

If an individual with gMG is symptomatic on pyridostigmine the next step is a trial of glucocorticoids followed by nonsteroidal immunosuppressive agents such as azathioprine, mycophenolate, cyclosporine, or tacrolimus: They can suppress the immune system, which is attacking the acetylcholine receptors. This reduces the symptoms of gMG, but can have severe side effects when taken long term.

Refractory/Severe gMG

  • Immunosuppressive agents as described above
  • Intravenous immune globulin (IVIG) or plasma exchange (PLEX) at regular intervals
  • Rituximab or cyclophosphamide
  • Soliris (eculizumab): FDA approved for the treatment of gMG in adult patients who have IgG autoantibodies and are acetylcholine receptor antibody-positive (AChR-Ab+). However, based on available data, eculizumab should be considered in only selected refractory patients with severe disease.

Drug overview

Efgartigimod is dosed by intravenous infusion weekly for four weeks, then adjusted based on patient symptoms. In the Phase 3 trial, individuals with anti-acetylcholine receptor (AChR) antibody positive gMG who received efgartigimod did significantly better than those who received placebo on the primary endpoint. This was measured by significant improvement in the Myasthenia gravis activities of daily living (MG-ADL) score during the first treatment cycle: 68% versus 30%24

In its Evidence Report, ICER concludes “that there is moderate certainty of a small or substantial net health benefit of efgartigimod added to conventional therapy… in adults with gMG positive for anti-AChR antibodies.3

As far as price to value, ICER estimated an incremental cost/quality-adjusted life year (QALY) of well over $1 million.3

PDUFA date:    December 17, 2021
Benefit:            Medical benefit

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References

  1. What Is Myasthenia Gravis? BioNews Serrvices, LLC COPYRIGHT © 2013-2021 ALL RIGHTS RESERVED. Accessed at: https://myastheniagravisnews.com/what-is-myasthenia-gravis/
  2. Howard JF, Bril V, Vu T, et al. Safety, efficacy, and tolerability of efgartigimod in patients with generalized myasthenia gravis (ADAPT): a multicenter, randomized, placebo-controlled, phase 3 trial. Lancet Neurology 2021; 20 (7): 526-536
  3. Tice JA, Nikitin D, Campbell J, Moradi A, Rind DM, Pearson SD, Agboola F. Eculizumab and Efgartigimod for the Treatment of Myasthenia Gravis: Effectiveness and Value; Draft Evidence Report. Institute for Clinical and Economic Review, July 22, 2021. https://icer.org/assessment/myasthenia-gravis/#timelin
  4. Tice JA, Nikitin D, Campbell J, et al. Eculizumab and efgartigimod for the treatment of myasthenia gravis: effectiveness and value.  Revised evidence report. September 10, 2021. Accessed in November 2021 at: https://icer.org/wp-content/uploads/2021/03/ICER_Myasthenia-Gravis_Revised-Evidence-Report_091021.pdf

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