Low-Dose Rituximab May Be Cost-Effective for Myasthenia Gravis

Autoimmune myasthenia gravis is typically treated with surgery, acetylcholine esterase inhibitors, corticosteroids, and immunosuppressive drugs like azathioprine and mycophenolate mofetil. Some patients have refractory disease and may require therapies like eculizumab (Soliris), which, while effective, is a particularly high-cost biologic that has no approved biosimilars in Europe or the United States, although biosimilars are advancing through clinical development. Rituximab, however, which is lower-cost than eculizumab and has multiple approved biosimilars, has also emerged as a promising treatment. 
The Center for Biosimilars Staff
December 28, 2019
Autoimmune myasthenia gravis (MG) is typically treated with surgery, acetylcholine esterase inhibitors, corticosteroids, and immunosuppressive drugs like azathioprine and mycophenolate mofetil. Some patients have refractory disease and may require therapies like eculizumab (Soliris), which, while effective, is a particularly high-cost biologic that has no approved biosimilars in Europe or the United States, although biosimilars are advancing through clinical development.

Rituximab, however, which is lower-cost than eculizumab and has multiple approved biosimilars, has also emerged as a promising treatment.

A number of case reports and retrospective studies have shown that rituximab is safe and effective in patients with MG, but optimal dosing has not been established, and regimens adapted from treatment for non-Hodgkin lymphoma have been used. However, based on emerging evidence, low-dose rituximab, administered at 6-month intervals, may be noninferior and may improve the cost-effectiveness of using rituximab in these patients.

A paper published recently in Therapeutic Advances in Neurological Disorders reports on a study that evaluated the efficacy and safety of repeated low-dose rituximab treatment, individualized by monitoring of CD19-positive B cells, in patients with MG that proved refractory to other treatments.

In the retrospective review of 17 patients with MG who were treated with rituximab at 2 teaching hospitals between 2013 and 2017, the treatment protocol comprised induction treatment with low-dose rituximab at a dose of 375 mg/m2 twice with a 2-week period followed by retreatment based on either B-cell repopulation or clinical relapse.

Following rituximab treatment, 11 patients achieved the primary end point of minimal manifestation or better with prednisolone at a dose of 5 mg per day or less after a median of 7.6 months (range, 2-17 months). Over a median follow-up of 24 months (range, 7-49 months), 30 retreatments were given. Six of these retreatments were on the basis of relapse without B-cell repopulation, 16 were given on the basis of repopulation without relapse, and 8 were given on the basis of both repopulation and relapse.

On a group level, say the researchers, B-cell recovery appeared to occur in parallel with relapse, but on an individual level, the association was modest.

“Considering the limited data on the optimal rituximab dose and retreatment schedule, our results are encouraging and have therapeutic implications for refractory MG,” write the authors. “Given the reduced costs and possibly lower risk of adverse effects, we propose that repeated treatment with low-dose rituximab guided by monitoring circulating B cells could be a cost-effective therapeutic option in patients with refractory MG.”

Reference
Choi K, Hong YH, Ahn SH, et al. Repeated low-dose rituximab treatment based on the assessment of circulating B cells in patients with refractory myasthenia gravis [published online September 18, 2019]. Ther Adv Neurol Disord. doi: 10.1177/1756286419871187.

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