Long-term remission with rituximab in refractory generalized myasthenia gravis
Juan Castiglione1, Fabio Adrian Barroso1, Patricio Brand1, Andrea Lautre1, Alejandro Kohler1
1Neurology, FLENI
Objective:
To assess long-term efficacy of rituximab (RTX) in the treatment of refractory generalized myasthenia gravis (MG).
Background:
RTX is a therapeutic option in MG, especially in patients without adequate response, either due to severity, refractoriness or inability to reduce doses of basal immunosuppressive drugs.
Design/Methods:

A retrospective study was performed in adult patients with refractory generalized MG referred to our center from January/2015 to October/2020 with a follow-up of at least 24 months. Anti-acetylcholine receptor (AChR) and anti-muscle-specific kinase (MuSK) autobodies were analyzed. The Myasthenia Gravis Status and Treatment Intensity (MGSTI) score was used to assess outcomes, and CD19/CD20+ B-cell counts were serially monitored.

Results:

Sixteen MG patients (13 = female; mean age = 45 years) treated with RTX were included. They were previously studied with autoimmune antibodies (AChR = 8 and MuSK = 8), and presented a median MGFA score of 4A-B. Patients were undergoing treatment with 2 immunosuppressants and they had received at least one cycle of intravenous immunoglobulin (10 requiring intensive care). Low-dose RTX protocols were used during induction (7 = 2000 mg, 7 = 1000 mg and 2 = 1500 mg), and only 5 patients received maintenance doses. During follow-up, all patients maintained undetectable CD20 levels at 6 and 12 months after induction, without new relapses. All patients presented MGFA-PIS and MGSTI scores ≤2; the earlier the treatment with RTX was initiated, the faster the score was reached.


Conclusions:
RTX is an effective therapeutic option, both in MG MuSK (being the 1st option in this case) and in refractory AChR. In our series, high doses of RTX induction or regular maintenance were not required to achieve undetectable CD20, attain remission or achieve minimal basal immunosuppressive treatment. Early initiation of RTX in selected patients could be associated with a more rapid and sustained clinical response over time.