Background Natalizumab is the first licensed treatment, given by infusion, monthly, for highly active relapsing-remitting multiple sclerosis or rapidly evolving severe MS. It is not a cure, its safety issues represent a relevant limitation and impose strict clinical surveillance mainly because of the risk of progressive multi-focal leukoencephalopathy (PML), (a potentially lethal brain disorder.

Purpose Review of use: effectiveness, safety, reason for start or switch.

Material and methods Retrospective observational study 2015–2018.

Treatment history, demographic and clinical data were collected from medical records

We assessed effectiveness by the change in expanded disability status scale (EDSS), defined by Fernandez et al: improvement, a decrease of ≥1 point, stability, a change of <1 point and worsening, an increase of 1≥point, and also by the number of patients with outbreaks during the year prior to treatment and at least 12 months after.

Safety was assessed by analysing the incidence of adverse reactions and risk for PML stratified in high, medium and low based on three major risk factors: duration of treatment >2 years, prior immunosuppressive treatment and positive serum JC virus antibodies.

Results Fifty-six patients, 57% female, mean age at diagnosis 26.4.

Eleven patients received Natalizumab as first option and 45 were switched because of lack of efficacy with one or two immunomodulatory drugs prior to Natalizumab.

Most patients were still ambulatory when they began treatment (median EDSS 2.00).

Mean treatment duration was 3.3 years (1–10 years).

Over the study period, the age of starting natalizumab has decreased and the total number of treated patients has increased from 31 to 56. Natalizumab was generally well tolerated, as only four left for the reason of inefficacy and one for PML.

Stabilisation of EDSS was achieved for 70% of patients:; only 10% showed worsening.

Forty patients showed no risk for PML (<1:10000) and moderate risk from the rest.

Ninety-three per cent had relapsed at least once in the year prior to natalizumab and 12 months after, the proportion decreased to 15%.

Conclusion Natalizumab provides efficacy in slowing disease progression and reducing relapses, effective particularly in patients with less disability and without prior treatment. As long as the risk of PML is managed effectively and patients are constantly informed about their benefit-risk level, it remains a valuable therapeutic option.

References and/or acknowledgements No conflict of interest.