Natalizumab treatment in relapsing-remitting multiple sclerosis: a thirteen-year experience in a low prevalence and mixed-race population MS center.

Introduction: Natalizumab (NTZ) is a humanized monoclonal antibody indicated for people with multiple sclerosis (pwMS) with poor response to first-line disease-modifying therapy (DMT) or naive-patients with highly active disease. Studies assuring its effectiveness and safety have been widely covered but data regarding low prevalence and mixed-race populations are scarce. Objectives: To evaluate NTZ treatment profile in a northeast Brazilian MS center. Methods: Observational and retrospective data from patients under NTZ treatment between July 2010 and March 2023, collected from a northeast Brazilian MS Center. Results: In total, 114 patients were enrolled, with a median follow-up time of 15 months (IQR 8-24). 77% were female, the median age was of 34 years old (IQR 29-42) and median disease duration 8.5 years (IQR 5-13). 73% patients had relapses 2-year prior NTZ initiation with median relapse number of 2 (IQR 1,5-3). NTZ was initiated in 28 naïve-patients (25%) and switched from other DMT in 86 (75%). Dimethyl Fumarate was the prior DMT in 31% patients, Fingolimod in 27%, Glatiramer in 23% and others DMT in 19%. 6% patients had well defined relapses during treatment and only 2% had radiologic activity. 12% patients had side effects, the most common being headache and itching. 27 patients discontinued treatment, 03 due failure, 13 due positive JCV serology, 8 due progression, one due side effects and two due pregnancy. 18% of patients presented EDSS worsening during follow-up (increase of >/=1 point in one year), 80% maintained stability and 2% had an improvement. Conclusion: Most patients remained clinically stable during NTZ treatment with few side effects reported. A minority interrupted treatment due failure, the most common discontinuation cause being JCV status and disability progression. Disease response to NTZ treatment and demographic data here presented matched previous studies confirming its safety and efficacy in the analyzed population.