The study, “Rituximab in Late‐Onset Myasthenia Gravis is Safe and Effective,” was published in the journal Muscle & Nerve.
Rituximab — marketed as Rituxan by Genentech and Biogen in the U.S., among others — works by decreasing the number of B-cells, which are the immune cells that produce antibodies. It is used in the treatment of some cancers and certain autoimmune diseases, such as rheumatoid arthritis. However, its effectiveness in LOMG is not clear.
Researchers at Cedars-Sinai Medical Center in Los Angeles, California, reviewed data from seven people with LOMG (five women, mean age at disease onset 66 years), who were seen between 2013 and 2018. All participants either did not respond to other immunotherapies or were unable to tolerate corticosteroids. Two patients were on monthly intravenous immunoglobulin and another was on twice-weekly plasma exchange. All were positive for anti-acetylcholine receptor (AChR) antibodies.
Prior to receiving rituximab, patients’ MG Foundation of America (MGFA) class ranged from class 2B to 5. In this scale, class 2B indicates mild muscle weakness mainly affecting oropharyngeal (mouth and pharynx) and/or respiratory muscles, while 5 indicates the need for intubation.
After a mean period of nearly 18 weeks on rituximab, all seven patients were at lower (less severe) classes, ranging from 0 (remission) to 2, which occurs when weakness affects muscles other than those of the eyes. Also, five patients experienced a reduction in anti-AChR antibodies levels up to 63%, which was associated with clinical improvement.
Five patients had no noteworthy side effects associated with rituximab treatment. One participant experienced itchiness and rash at the injection site, but was able to complete treatment. Another participant developed pneumonia, which the researchers said probably was due to prolonged ventilator use.
“All patients had significant clinical improvement with rituximab and were able to reduce or discontinue their daily or monthly maintenance medications without any further myasthenic crises or hospitalizations,” the researchers wrote. “All patients expressed great satisfaction with this approach, achieving full function after months to years of weakness and treatment-related complications.”
This study’s limitations should be noted. According to the researchers, the group of patients was small and the study lacked a control group. Also, because rituximab is used off-label to treat MG, there was no standardized dosing protocol.
“Our findings raise the possibility that rituximab has the potential to be considered as a first-line immunotherapy for older patients with generalized AChR-positive MG,” the scientists added. “Further randomized-control trials are needed to confirm the safety and efficacy of rituximab in this age group.”
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