BACKGROUND

Natalizumab is the first alpha4 integrin antagonist in a new class of selective adhesion-molecule inhibitors. We report the results of a two-year phase 3 trial of natalizumab in patients with relapsing multiple sclerosis.

METHODS

Of a total of 942 patients, 627 were randomly assigned to receive natalizumab (at a dose of 300 mg) and 315 to receive placebo by intravenous infusion every four weeks for more than two years. The primary end points were the rate of clinical relapse at one year and the rate of sustained progression of disability, as measured by the Expanded Disability Status Scale, at two years.

RESULTS

Natalizumab reduced the risk of sustained progression of disability by 42 percent over two years (hazard ratio, 0.58; 95 percent confidence interval, 0.43 to 0.77; P<0.001). The cumulative probability of progression (on the basis of Kaplan-Meier analysis) was 17 percent in the natalizumab group and 29 percent in the placebo group. Natalizumab reduced the rate of clinical relapse at one year by 68 percent (P<0.001) and led to an 83 percent reduction in the accumulation of new or enlarging hyperintense lesions, as detected by T2-weighted magnetic resonance imaging (MRI), over two years (mean numbers of lesions, 1.9 with natalizumab and 11.0 with placebo; P<0.001). There were 92 percent fewer lesions (as detected by gadolinium-enhanced MRI) in the natalizumab group than in the placebo group at both one and two years (P<0.001). The adverse events that were significantly more frequent in the natalizumab group than in the placebo group were fatigue (27 percent vs. 21 percent, P=0.048) and allergic reaction (9 percent vs. 4 percent, P=0.012). Hypersensitivity reactions of any kind occurred in 25 patients receiving natalizumab (4 percent), and serious hypersensitivity reactions occurred in 8 patients (1 percent).

CONCLUSIONS

Natalizumab reduced the risk of the sustained progression of disability and the rate of clinical relapse in patients with relapsing multiple sclerosis. Adhesion-molecule inhibitors hold promise as an effective treatment for relapsing multiple sclerosis. (ClinicalTrials.gov number, NCT00027300.).

OBJECTIVE

Impaired ambulation is a prominent disabling symptom of multiple sclerosis and can lead to reduced quality of life. Whether natalizumab, a monoclonal antibody shown to reduce disease activity in relapsing-remitting multiple sclerosis, could impact ambulation performance was examined.

METHODS

A prospective open-label study, TIMER, was conducted in natalizumab-naive patients (n = 215). The timed 25-foot walk (T25FW) and timed 100-m walk (T100MW) were assessed at baseline and at weeks 24 and 48 of natalizumab therapy, together with Expanded Disability Status Scale scores. The effects of natalizumab on T25FW performance were also examined in a retrospective analysis of natalizumab-treated patients (n = 627) and placebo control patients (n = 315) from the AFFIRM study.

RESULTS

In TIMER, a significant increase from baseline in T25FW speed was seen at week 24 (P = 0.0074) and in T100MW speed at weeks 24 and 48 (both P < 0.001). A greater proportion of patients showed clinically meaningful increases (≥20%) in walking speed on the T100MW (25%) than on the T25FW (13%) at week 48 (P = 0.032). In AFFIRM, natalizumab increased the proportion of patients with ≥20% confirmed improvement in T25FW speed at year 2 by 78% versus placebo (P = 0.0133).

CONCLUSIONS

Natalizumab increased walking speed in patients with relapsing-remitting multiple sclerosis. The T100MW may be more sensitive to changes in ambulation capacity than the T25FW, and both tests appear to detect clinically meaningful improvements in ambulatory function.