Alemtuzumab following natalizumab is more effective in adult-onset than paediatric-onset multiple sclerosis

Background: Paediatric-onset multiple sclerosis (POMS) therapeutic approach derives from of adult-onset multiple sclerosis (AOMS) tailored algorithms. Objectives: To evaluate in a common clinical scenario the efficacy and safety of alemtuzumab (ALZ) in POMS and AOMS. Methods: All patients switching from natalizumab (NTZ) to ALZ for safety concerns (high anti-John Cunningham Virus Antibody Index value, anti-JCV Index) were enrolled in this single-centre, retrospective, case-control open-label study. Results: Ten POMS and 27 AOMS were followed up for 51.3 months. After month 12, we found a lower risk of clinical or radiological relapses among AOMS patients and among patients with older age at ALZ (both p < 0.05). Survival analysis revealed an increased risk of relapse in POMS compared with AOMS (logrank p = 0.00498) and patients starting ALZ before age 22.75 years than the elder ones (logrank p = 0.0018). Survival analysis did not disclose any difference between AOMS and POMS (logrank p = 0.27) in terms of progression independent of any relapse activity (PIRA). In addition, no evidence of relapse-associated worsening was observed. Autoimmune events were reported by 5 AOMS and no POMS (29.4% versus 0.0%, p = 0.057), and survival analysis was not significant (logrank p = 0.0786). Conclusion: ALZ seems more effective in AOMS than in POMS following NTZ. These findings underrate ALZ effectiveness when shifting from NTZ in POMS.