While there is no cure for myasthenia gravis, this disorder can be managed with treatment. Current treatment options include a thymectomy, C5 protein inhibitors, and intravenous immune globulins (among others).

Roche and Chugai Pharmaceutical Co., Ltd have been working to determine whether Enspryng (satralizumab) could be leveraged as a treatment for generalized myasthenia gravis (gMG). Enspryng is currently used to treat adults with neuromyelitis optica spectrum disorder (NMOSD) who are aquaporin-4 (AQP4) antibody positive.

However, Jonathan Gardner reported in Biopharma Dive that Enspryng performed poorly in the Phase 3 LUMINESCE clinical study for gMG. 188 individuals enrolled in the study. Over a 24-week period, participants received either Enspryng or a placebo. According to a news release from Chugai:

Statistically significant data was observed in its primary endpoint; however the results did not reach our expectations on the degree of clinical benefit…Detailed results will be presented as an oral Emerging Science abstract at the American Academy of Neurology (AAN) 2024 Annual Meeting on 15 April in Denver, Colorado.

What is Myasthenia Gravis (MG)?

The name myasthenia gravis comes from the Greek and Latin words for “grave muscle weakness.” This rare and chronic autoimmune neuromuscular disorder causes muscle weakness and fatigue in voluntarily controlled muscles. It occurs when the body creates antibodies that block or destroy acetylcholine receptors at the neuromuscular junction. As a result, the muscles can’t receive signals from the brain. There are different subsets of myasthenia gravis, including generalized, ocular, transient neonatal, juvenile, and congenital. The generalized form is most common, accounting for 85% of cases. It is considered refractory generalized myasthenia gravis if people do not respond to treatment. MG is more common in women under 40 years old and men over 60 years old.

Symptoms in MG worsen with more activity and generally improve with rest. However, they may become progressively worse over time. These symptoms may include:

• Drooping eyelids
• Double vision that often resolves if one eye is closed
• Weakness of eye muscles
• Impaired speech
• Dysphagia (difficulty swallowing)
• Muscle weakness and fatigue
• A “mask-like” appearance where a smile may look like a snarl
• Shortness of breath
• Slurred speech
• Changed gait

Some people with myasthenia gravis develop life-threatening breathing difficulties due to muscle weakness in the chest wall. This is known as myasthenic crisis and can be triggered by infection, stress, surgery, or even medication. The National Institute of Neurological Disorders and Stroke says that 15-25% of people with MG will have at least one myasthenic crisis, with up to 50% unable to identify a trigger.