Natalizumab in acute ischemic stroke (ACTION II): A randomized, placebo-controlled trial

OBJECTIVE: We evaluated the effect of 2 doses of natalizumab on functional outcomes in patients with acute ischemic stroke (AIS). METHODS: In this double-blind phase 2b trial, patients with AIS aged 18–80 years with NIH Stroke Scale scores of 5–23 from 53 US and European sites were randomized 1:1:1 to receive a single dose of 300 or 600 mg IV natalizumab or placebo, with randomization stratified by treatment window (≤9 or >9 to ≤24 hours from patient's last known normal state). The primary endpoint was a composite measure of excellent outcome (modified Rankin Scale score ≤1 and Barthel Index score ≥95) at day 90 assessed in all patients receiving a full dose. Sample size was estimated from a Bayesian model; p values were not used for hypothesis testing. RESULTS: An excellent outcome was less likely with natalizumab than with placebo (natalizumab 300 or 600 mg odds ratio 0.60; 95% confidence interval 0.39–0.93). There was no effect modification by time to treatment or use of thrombolysis/thrombectomy. For natalizumab 300 mg, 600 mg, or placebo, there were no differences in incidence of adverse events (90.0%, 92.1%, and 92.3%, respectively), serious adverse events (25.6%, 32.6%, and 20.9%, respectively), or deaths (6.7%, 4.5%, and 5.5%, respectively). CONCLUSIONS: Natalizumab administered ≤24 hours after AIS did not improve patient outcomes. CLINICALTRIALS.GOV IDENTIFIER: NCT02730455 CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that for patients with AIS, an excellent outcome was less likely in patients treated with natalizumab than with placebo.