An open-label trial of rituximab (Rituxan®) in multifocal motor neuropathy

Multifocal motor neuropathy (MMN) is an acquired demyelinating motor neuropathy. Intravenous immunoglobulin (IVIg) has been found to be safe and effective. Rituximab, a genetically engineered monoclonal antibody against CD-20 antigen, has been reported effective in immune disorders including MMN. We performed an open-label trial to determine if rituximab would reduce the IVIg requirement, disability, and impairment, and be safe in patients with MMN. Six MMN patients, who were on periodic IVIg treatments, received two doses of IV rituximab (1,000 mg) given 2 weeks later. Assessments were performed at baseline and at 2, 4, 6, 8, 10, and 12 months. The primary outcome was total amount of IVIg used during the 12-month study compared to the 12 months prior. Secondary outcomes included changes in Medical Research Council (MRC) sum scores, grip strength, disability and handicap scores, and safety. There was no significant change in IVIg use, MRC sum score, grip strength, overall disability sum score, or Rotterdam handicap scale. One patient developed a hypersensitivity reaction during the first infusion that responded to adjustments in the infusion rate and treatment with diphenhydramine and acetaminophen. We conclude that rituximab can be safely given to people with MMN but in this pilot study we were unable to reduce the amount of IVIg required, at least in the regimen used.