The drug rituximab (sold under the brand name Rituxan, among others) may bring long-term relief for patients with a rare form of myasthenia gravis (MG) caused by muscle-specific kinase (MuSK) antibodies, according to a recent study published in Frontiers in Immunology.
MuSK antibodies are proteins produced by the immune system that mistakenly target the MuSK protein, a protein crucial for communication between nerves and muscles. This type of MG often causes breathing problems and muscle weakness.
In this early study, 10 women with MuSK-MG received low-dose rituximab, which targets certain immune cells that produce harmful antibodies. Within one month, nine out of 10 patients showed clear improvement in daily activities, and all improved by the second month. By two years, most had minimal or no symptoms, and most were able to stop taking steroid medication (prednisone), thus lowering the risk of long-term side effects.
No side effects from rituximab were reported in any of the patients.
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MuSK-MG is rare, accounting for just 1%–10% of MG cases. Compared with another form of MG caused by acetylcholine receptor (AChR) antibodies, MuSK-MG patients in this study had more severe symptoms at the start.
Standard treatments, like acetylcholinesterase inhibitors, often don’t work as well in patients with MuSK-MG and can cause side effects. Steroids and other immunosuppressants can help but may require high doses and long-term use, increasing the risk of complications.
“In patients with MuSK-MG, low-dose rituximab may be associated with long-term and sustained clinical improvement,” the researchers said.
However, they cautioned that this was a small study without a comparison group, so larger studies are needed to confirm these results and fine-tune dosing schedules.
“Despite the existing limitations, our findings add to the increasing evidence supporting the use of rituximab in MuSK-MG and lay a foundation for future research aimed at optimizing treatment strategies and enhancing patient outcomes,” the researchers said.
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