Predictors of response to first-line immunosuppressive therapy in neuromyelitis optica spectrum disorders

Background: Azathioprine (AZA) and mycophenolate mofetil (MMF) are the most commonly used first-line therapies for patients with neuromyelitis optica spectrum disorders (NMOSD). However, some patients experience a relapse following AZA or MMF treatment. Objectives: To identify factors that predict a response to AZA or MMF in NMOSD. Methods: We retrospectively evaluated medical records from 116 patients who were initially treated with AZA or MMF for at least 6months. Poor response was defined as 2 relapses or 1 severe relapse. Results: Among the 116 patients, 40 (34%) were classified as poor responders. Logistic regression analyses revealed that a poor response was independently associated with a pre-treatment history of a severe attack (p<0.001) and a younger age at disease onset (p=0.022). Among the 40 patients with a poor response, 29 (73%) switched to rituximab, and only 3 (10%) had a poor response to rituximab. Conclusion: Patients with a pre-treatment history of a severe attack and a younger age of onset exhibited an increased risk of a poor response to AZA or MMF therapy. Identifying patients who are unlikely to respond to AZA or MMF therapy may allow for treatment with more potent therapies that improve treatment outcomes.