Soliris (eculizumab), developed by Alexion Pharmaceuticals, is being investigated as a potential treatment for drug-resistant generalized myasthenia gravis (gMG). Although the European Commission has approved Soliris to treat gMG, the U.S. Food and Drug Administration (FDA) has not — though it has approved Soliris for the treatment of paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.
How Soliris works
Myasthenia gravis (MG) is an autoimmune condition, in which the body’s immune system attacks parts of the nervous system that transmit messages between muscles and the brain. This leads to muscle weakness and a lack of control over muscles, including those involved in swallowing, breathing and talking.
Normally, to pass on a message to a muscle, motor neurons release a chemical called acetylcholine at the neuromuscular junction — the point where the nerve and muscle cells interact.
Acetylcholine binds to acetylcholine receptors (AChRs) found on muscle cells, which causes the muscles to contract. In most MG patients, the immune system starts to produce antibodies — a type of immune protein that interacts with a specific target — that prevent the AChRs from working or even destroy them.
Soliris is designed to block part of the immune system called the terminal complement cascade, consisting of a series of reactions that help trigger the damaging immune response seen in MG. Soliris binds to and inhibits the cleavage of a protein called C5 — an essential step at the start of the cascade.
Soliris in clinical trials
The European Commission approved Soliris on Aug. 21, 2017, as the first treatment for gMG. In January 2017, Alexion filed a supplementary biologics license application (sBLA) to the FDA to extend the drug’s approval to include treatment for gMG.
These applications were based on the results of a key Phase 3 clinical trial (NCT01997229) called REGAIN that aimed to assess the drug’s safety and efficacy. The randomized, double-blind, placebo-controlled trial enrolled 125 patients with gMG who did not respond to other MG treatments, who were given either Soliris or a placebo for 26 weeks.
The study did not achieve significance in the primary endpoint, which was a change in MG activities of daily living (MG-ADL) score. However, the study did show a significant reduction in disease severity in patients treated with Soliris compared those on placebo, using other measures including a significant change in the MG Composite (MGC) score and the 15-item MG quality of life (MG-QOL15) score.
Side effects associated with Soliris include headache, dizziness, fever, nausea, infections, fatigue, bladder pain and the common cold.
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