Treatment effect of natalizumab on relapse outcomes in multiple sclerosis patients despite ongoing MRI activity

Natalizumab treatment significantly reduced the annualised relapse rate and MRI activity over 2 years compared with placebo in phase III trials when administered as monotherapy in AFFIRM or in combination with interferon beta-1a (IFN beta) in SENTINEL. The post hoc analyses reported here sought to determine the effect of natalizumab treatment on relapse activity in the minority of patients who continued to show MRI activity (ie, >= 1 gadolinium enhancing (Gd+) lesions or new or enlarging T2 hyperintense lesions) over 2 years in these trials. These analyses demonstrated that natalizumab treatment, both alone (AFFIRM) and in combination with IFN beta (SENTINEL), resulted in a reduced annualised relapse rate despite the presence of Gd+ lesions (p=0.004 and p=0.008, respectively) or new or enlarging T2 hyperintense lesions (each p < 0.0001). Thus patients treated with natalizumab show clinical benefit even in the presence of continued MRI activity. Long term clinical outcome of these patients has not been studied.