Cladribine suppresses disease activity in neuromyelitis optica spectrum disorder: a 2-year follow-up study.

BACKGROUND AND PURPOSE: Neuromyelitis optica spectrum disorder (NMOSD) is a difficult condition to treat. Cladribine selectively and transiently depletes B and T lymphocytes, leading to long-lasting immune reconstitution. This report describes observations from 24 months of follow-up after cladribine in NMOSD patients. METHODS: This is a retrospective analysis of a case series including 12 seropositive patients with NMOSD. Patients were given cladribine by subcutaneous injections in a series of several 2-day cycles of 20 mg administered at intervals of 4-6 weeks. Thus, the full treatment course delivered a cumulative bioavailable dose similar to that approved for treatment of multiple sclerosis. Annualized relapse rate (ARR), disability (Expanded Disability Status Scale [EDSS] score) and safety in the 24 months preceding and the 24 months following the initiation of cladribine treatment were assessed. RESULTS: The mean ARR in the 24 months preceding cladribine treatment was 1.04 (95% confidence interval [CI] 0.67-1.62). The mean ARR in the 24 months following initiation of cladribine treatment was 0.21 (95% CI 0.08-0.56). The ratio in the rate of events post versus prior cladribine initiation was 0.20 (95% CI 0.07-0.59) and highly significant (p = 0.0073). The EDSS score did not change over the follow-up period (2.5 ± 1.7; mean ± SD) compared to baseline (2.5 ± 1.5; mean ± SD). No serious adverse events considered to be linked to cladribine were observed during follow-up. CONCLUSIONS: Cladribine was safe in NMOSD patients over a 2-year observation period. Cladribine treatment was associated with clinical stabilization, as evidenced by significantly decreased ARR and no progression of EDSS score.