Patients with myasthenia gravis (MG) and anti-muscle-specific kinase (MuSK) antibodies typically have a more severe disease presentation, with early bulbar, neck, and respiratory muscle weakness. Results from a multicenter, blinded, prospective study published in Neurology provide evidence that treatment with rituximab in these patients may increase the likelihood of more favorable clinical outcomes compared with the use of other, more traditional therapies.
The analysis included 55 patients with anti-MuSK MG evaluated between January 1, 2005, and January 1, 2015 at 10 neuromuscular centers. Baseline characteristics were similar between the rituximab treatment group (n=24) and controls (n=31). The median duration of follow-up was >3.5 years in both groups.
The primary clinical outcome measure was the Myasthenia Gravis Status and Treatment Intensity (MGSTI), which combines the Myasthenia Foundation of American postintervention status with the number and the dosages of additional immunosuppressant treatments used. An MGSTI level ≤2 represented a favorable outcome.
At their last clinic visit, 58% (14 of 24) of rituximab-treated patients vs 16% (5 of 31) of controls reached the primary outcome (P =.002). The number needed to treat to achieve the primary outcome at the final visit was 2.4. The investigators noted that at last visit, 29% (7 of 24) of patients in the rituximab group were taking prednisone (mean dose, 4.5 mg/day) compared with 74% (23 of 31) in the control group (mean dose, 12.7 mg/day; P =.001 and P =.005, respectively).
The results offer class IV evidence that the use of rituximab therapy in patients with anti-MuSK MG is positively associated with the probability of a favorable outcome.
Hehir MK, Hobson-Webb LD, Benatar M, et al. Rituximab as treatment for anti-MuSK myasthenia gravis: Multicenter blinded prospective review. Neurology. 2017;89(10):1069-1077.