Long-term follow-up (up to 11 years) of an Italian pediatric MS cohort treated with natalizumab: a multicenter, observational study

Background Natalizumab (NAT) has a strong impact on disease activity of aggressive pediatric multiple sclerosis (MS), with no difference in safety profile compared to adult MS. However, available data are limited by short follow-up. Our aim was to report long-term follow-up data (up to 11 years) of a large Italian pediatric MS cohort treated with NAT. Materials and methods We retrospectively collected data of pediatric MS patients treated with NAT included in a previous study and prospectively followed in Italian MS centers. We compared disease activity pre, during, and post-NAT and we performed survival analyses of time to evidence of disease activity (EDA) during NAT, time to reach EDA post-NAT, and time to NAT discontinuation. Results Ninety-two patients were included from 19 MS centers in Italy. At NAT initiation, cohort's characteristics were as follows: 55 females; 14.7 +/- 2.4 (mean +/- SD) years of age; 34 naive to disease modifying therapies; 1-year pre-NAT annualized relapse rate (ARR): 2.2 +/- 1.2; EDSS (median [IQR]): 2.5 [2.0-3.0]; gadolinium-enhancing lesions: 2 [1-5]; 41 JCV positives. During NAT treatment (61.9 +/- 35.2 mean infusions), ARR lowered to 0.08 +/- 0.23 (p < 0.001), EDSS score to 1.5 [1.0-2.5] at last infusion (p < 0.001), and 51% patients had EDA (21% after 6 months of rebaseline). No serious adverse events were reported. Forty-nine patients discontinued NAT, mainly due to PML concern; the majority (29/49) had disease reactivation in the subsequent 12 months, of which three with a clinical rebound. Conclusion NAT treatment maintains its high efficacy for a long time in pediatric MS patients, with no new safety issues.