Comparison of Annual Relapse Rate, Expanded Disability Status Scale, and Side Effects Between Azathioprine and Rituximab in Patients With Neuromyelitis Optica Spectrum Disorders

Neuromyelitis Optica Spectrum Disorder (NMO-SD) is a recurrent inflammatory demyelinating disease affecting the central nervous system. The disease is clinically recognized by optic neuritis and transverse myelitis and is associated with high risk of mortality. Each attack worsens patients' disability. This means that after 5 years of the disease onset, half of patients need to use wheelchair and approximately 50% of them become blind.

Considering that the disease can be disabling for patients, the maintenance treatment should be applied in addition to treatment of acute attacks, in order to prevent future recurrences. Acute attacks are usually treated with high doses of intravenous corticosteroids. Plasmapheresis is also used when patients fail to response to corticosteroids. B lymphocyte inhibitors are used as the maintenance therapy in these patients. First line therapeutic medications include azathioprine and rituximab which are being recommended for long term therapy and second line medications include methotrexate and mycophenolate mofetil.

Azathioprine is an immune-modulatory agent which is available in the oral form and don't require hospitalization to be administered, however, because of side effects such as bone marrow suppression and hepatotoxicity, periodic check of blood cells and liver enzymes are needed. Rituximab is a cluster of differentiation antigen 20 inhibitor which leads to decreased B lymphocytes and antibody in patients. This medication is only available in the injectable form and needs hospitalization to be administered. Close monitory is needed during the administration considering severe side effects such as allergic reactions and respiratory distress. However, laboratory tests are not needed in patients taking rituximab although it is more expensive than azathioprine. No clinical trial has been performed previously to compare clinical efficacy of these two drugs in NMO-SD patients. Therefore, we aimed to compare their efficacy through a randomized clinical trial.