Wearing-off at the end of natalizumab dosing interval and risk of MS disease activity: A prospective 1-year follow-up study.

Natalizumab effectively prevents disease activity in relapsing-remitting multiple sclerosis by binding α4 integrin and inhibiting leukocyte migration to the central nervous system. We recently reported an association between low natalizumab receptor occupancy and subjective wearing-off symptoms at the end of the 4-week dosing interval. Here, we aimed to evaluate the short-term risk of disease activity in a 1-year prospective follow-up of the same patient cohort (n = 40). We found that all patients available for follow-up after one year (n = 35) fulfilled the criteria for no evidence of disease activity (NEDA). Thus, wearing-off symptoms were not associated with increased short-term risk of disease activity. Longer follow-up in a larger patient cohort is required to establish whether therapeutic efficacy is maintained in patients with wearing-off symptoms.