Natalizumab wearing-off symptoms: effect of extend interval dosing during Sars-CoV-2 pandemic.

Background: Many patients treated with Natalizumab experience wearing-off symptoms (WoS) towards the end of the administration cycle. During the pandemic we advised and asked patients undergoing treatment with Natalizumab if they wanted to be shifted from a standard interval dosing (StID of 4 weeks) to an extended interval dosing (ExID of 5-6 weeks), regardless of their JCV index. Our main objective was to study prevalence and incidence of WoS when ExID was adopted.

Methods: We enrolled 86 patients, from May 2020 to January 2021, evaluated at baseline and during a 6 months follow-up with a survey focused on WoS, Fatigue Severity Scale (FSS), Expanded Disability Status Scale (EDSS) and MRI.

Results: Among the 86 patients, 32 (37.2%) reported WoS. Most common one was fatigue (93.7%). Mean EDSS was higher in the group reporting WoS (3.8 WoS vs 3.1 non-WoS, p < 0.05). Sphincterial function was the EDSS item that significantly differed between the WoS group and the non-WoS group (1.4 WoS vs 0.6 non-WoS, p < 0.001). WoS correlate with the FSS scale (p < 0.001).

Conclusion: Adopting an extended interval dosing does not result in significantly different occurrence of WoS between the ExID and the StID populations, in our cohort of patients. Interestingly, there is a strong correlation between WoS and a higher EDSS and FSS. Safety and efficacy of Natalizumab with ExID are relatively preserved in our study.