The U.S. Food and Drug Administration (FDA) has approved eculizumab (Soliris) as a treatment for adult patients with generalized myasthenia gravis (gMG) who are anti-acetylcholine receptor (AchR) antibody-positive.

Approval was granted to Alexion Pharmaceuticals, Inc. and was based on results from their phase 3, placebo-controlled REGAIN study.

Myasthenia gravis (MG) is a progressive autoimmune disease that begins with weakness in the muscles that control the eyes and eyelids and often progresses to a more severe form, generalized myasthenia gravis (gMG), which affects the head, neck, trunk, limb, and respiratory muscles.

Current treatments effectively control the symptoms of MG, however, those options do not work for about 10 to 15 percent of patients with anti-AchR antibody-positive gMG.

That subset of patients suffer from significant unresolved disease symptoms, such as difficulties seeing, walking, talking, swallowing, and breathing. Exacerbations of these symptoms may require hospitalization and intensive care and may be life-threatening.

A disabling neuromuscular disorder

In patients with anti-AchR antibody-positive gMG, the body’s own immune system turns on itself to produce antibodies against AchR, a receptor located on muscle cells at the neuromuscular junction (NMJ) and used by nerve cells to communicate with the muscles these nerves control.

The binding of these antibodies to AchR activates the complement cascade, another part of the immune system, which leads to a localized inflammation and destruction of the muscle membrane at the NMJ.  As a result, the communication between nerve and muscle is impaired, which in turn leads to a loss of normal muscle function.   

According to the company, Soliris works by selectively inhibiting the terminal complement cascade, targeting a critical underlying cause of the disease.

“It is exciting that patients who have not responded adequately to existing therapies will now have a new treatment option that was shown in clinical studies to improve patients’ symptoms, their ability to carry out activities of daily living and their quality of life,” said Professor James F. Howard, M.D., Department of Neurology at the University of North Carolina, Chapel Hill, and lead investigator in the clinical development of this new indication, in a statement.

Also commenting in the statement, Nancy Law, chief executive officer of the Myasthenia Gravis Foundation of America (MGFA) said: “This is a landmark day for the members of the U.S. myasthenia gravis community, who have not seen a therapy approved for generalized myasthenia gravis in more than 60 years.”  

Soliris is already approved in the European Union (EU) for the treatment of refractory gMG in adults who are anti-AchR antibody-positive as well as for patients with the ultra-rare disorders paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS).

The treatment is one of the most expensive therapies worldwide, costing more than $500,000 per year.