OBJECTIVES : Natalizumab is an effective treatment for relapsing remitting multiple sclerosis (RRMS). The aim of this study was to characterize evolution of natalizumab utilization between 2012 and 2016 exploring patients’ characteristics and yearly infusions number.

METHODS : A retrospective observational cohort study was conducted using two clinical registries from two large MS centers, one in North and one in South of Italy. All patients with RRMS and a first prescription of natalizumab between 2012-2016 were included in the study and followed-up until last visit at the MS center or December 2017. Natalizumab use was described with regards to clinical and demographic characteristics of patients in treatment and yearly infusions number.

RESULTS : A total of 324 patients (72.5% female) starting natalizumab treatment between 2012-2016 were identified. The mean(SD) age at MS diagnosis and first natalizumab prescription was 33.5 (10.7) and 38.0 (10.9) respectively. Thirty-six patients reported a first prescription in 2012; from 2013 to 2016, we observed about 70 new patients each year. Within all new treated patients with Natalizumab, the percentage of naïve patients increased from 17% in 2012 to 35% in 2016 (overall mean 29%); moreover, 27.8% of patients reported an EDSS≤2, at last visit with EDSS available, before started natalizumab in 2012 and this number increased to 61.8% in 2016. The mean (range) natalizumab yearly infusions number decreased from 13.7 (11.6-13.8) in 2012 to 9.8 (8.0-10.2) infusions in 2016 (overall mean 10.7 [9.7-11.3]). In the first year of treatment, natalizumab patients received mean 12.6 infusions. While, in patients with at least one year of treatment, the mean dosing decreased from 11.3 infusions in 2013 to 8.8 infusions in 2016.

CONCLUSIONS : The study results support an evolution in natalizumab use in clinical practice, suggesting an earlier use of natalizumab in the disease course and a reduction of yearly infusions number since 2012 to 2016.