Rituxan Leads to High Rates of Clinical Remission in MG Patients, Study Reports

Treatment with Rituxan (rituximab) led to high rates of clinical remission without posing significant side effects in a group of patients with myasthenia gravis (MG), a study shows.

The study, “High efficacy of rituximab for myasthenia gravis: a comprehensive nationwide study in Austria,” was published in the Journal of Neurology.

Myasthenia gravis is an autoimmune disease caused by the abnormal production of antibodies against acetylcholine receptors (AchRs) or against muscle-specific tyrosine kinases (MuSKs). This leads to muscle weakness, a lack of muscle endurance, and extreme fatigue.

For this reason, most MG patients must remain on immunosuppressive therapies for long periods of time to keep their immune systems at bay. However, many immunosuppressive treatments currently used in the clinic, such as azathioprine or cyclosporine, may have serious side effects, take too long to act, or completely fail to keep MG under control.

“Rituximab (RTX), a monoclonal antibody that leads to rapid depletion of B-cells [immune cells responsible for the production of antibodies] and their precursors, has emerged as a potentially efficacious off-label treatment option for patients with MG. The increasing use of (RTX) in many centres worldwide still lacks supportive evidence from randomized trials,” the researchers wrote.

In the study, a team of Austrian researchers set out to describe the use, efficacy, and safety of Rituxan in a group of adult MG patients in a real-world setting.

The retrospective, nationwide study was based on the analysis of anonymized medical records of 56 MG patients who had been treated with Rituxan and monitored for a period of at least three months. The Myasthenia Gravis Foundation of America Postintervention Status scale was used to evaluate patients’ clinical outcomes.

More than half of the patients (60.7%) were women, with a median age at MG diagnosis of 41.5 years old and a median age at the start of treatment of 47.5 years old. Most patients produced antibodies against AchRs (69.6%), and some produced antibodies against MuSKs (25%). A small portion of patients (5.4%) were double seronegative, that is, they did not produce antibodies targeting AchRs or MuSKs.

Before beginning treatment with Rituxan, most patients (83.9%) had already been treated with plasma exchange, immune adsorption, or immunoglobulins.

Analyses showed that after three months of treatment with Rituxan, approximately a quarter of the patients (26.4%) went into clinical remission. At the last follow-up visit (median of 20 months after starting the treatment), almost half of the patients had already gone into clinical remission (42.9%), while a fourth (25%) reported only minimal MG symptoms.

Interestingly, clinical remission was more frequently observed among patients producing antibodies against MuSKs (71.4%), compared with those producing antibodies against AchRs (35.9%).

The treatment was generally safe and well-tolerated by patients. The most common adverse events associated with the therapy included infusion site reactions, upper respiratory infections, and chronic pain syndromes. One of the patients died during follow-up, presumably due to heart disease.

“In conclusion, this study found that RTX is a well tolerated, safe, efficacious, and relatively fast-acting treatment for patients with MG. Benefit from RTX was greatest in [patients producing] MuSK [antibodies]. Placebo-controlled, randomized trials are needed to further clarify the role of RTX in MG,” the researchers wrote.