Study Finds Long-Term Rituximab Safe, Effective in Treating Autoimmune Neurological Diseases

B cells play a key role in many autoimmune diseases, including the immune-mediated neurological disorders neuromyelitis optica (NMO), multiple sclerosis (MS), and myasthenia gravis (MG). Rituximab, which causes short-term depletion of circulating naïve and memory B cells through antibody-dependent cell-mediated cytotoxicity, complement mediated cytotoxicity, and induction of apoptosis, has been successfully used “off label” to treat diseases driven by B-cell dysregulation. The promising results of some studies on the use of rituximab in these disorders has generated interest in further developing B-cell depleting or anti-proliferative agents for use in these indications, but concerns remain about the safety of using rituximab or similar agents for long periods.

A study newly published in PLOS One sought to investigate the long-term safety, incidence of infections, and malignancies in patients receiving continuous therapy with rituximab over periods of 36 months to 7 years. The retrospective study was conducted at 2 tertiary centers in Detroit, Michigan, and Chicago, Illinois, and involved 29 patients with diagnoses of MS (n = 5), NMO (n = 21), or MG (n = 3) who received rituximab at doses of 1000 mg via intravenous administration every 6 to 9 months after an initial course of the drug. The mean duration of treatment was 51.3 months (±12.2 months), and the mean number of rituximab treatment cycles was 8.83 (±2.85).

During the observation period:

• There were 32 reported adverse events (AEs) in total, comprising upper respiratory tract infections, urinary tract infections (UTI), and cellulitis.
• 4 serious AEs (which required IV antibiotics or hospitalization) were reported, and comprised pneumonia, UTIs, and sinusitis.
• 3 of the serious AEs were reported after 9 cycles of rituximab, and 1 was observed after 11 cycles. None of the AEs were considered dose-related.
• No cases of progressive multifocal leukoencephalopathy or malignancies were observed throughout the observation period.
• Repeated rituximab infusions were well tolerated over time, with no significant infusion reactions.

The study’s authors concluded that rituximab was well tolerated over time in patients with NMO, MS, and MG; that AEs and SAEs remained low throughout the observation period; and that patients remained clinically stable while receiving continuous rituximab infusions. Though the study was small, it makes an important contribution, say the authors, to documenting the long-term tolerability and efficacy of rituximab as a viable option for the treatment of immune-mediated neurological diseases. Further studies will be needed to corroborate these results.