Intravenous tenecteplase for acute ischemic stroke between 4.5 and 6 h of onset (EXIT-BT2): Rationale and Design

Abstract

Rationale: To date, the benefit of intravenous thrombolysis for acute ischemic stroke (AIS) patients without advanced neuroimaging selection is confined to within 4.5 h of onset. Our phase II EXIT-BT (Extending the tIme window of Thrombolysis by ButylphThalide up to 6 h after onset) trial suggested the safety, feasibility, and potential benefit of intravenous tenecteplase (TNK) in AIS between 4.5 and 6 h of onset. The EXIT-BT2 trial is a pivotal study undertaken to confirm or refute this signal. Aim: To investigate the efficacy and safety of TNK for AIS between 4.5 and 6 h of onset with or without endovascular treatment. Sample size estimates: A maximum of 1440 patients are required to test the superiority hypothesis with 80% power according to a two-sided 0.05 level of significance, stratified by age, sex, history of diabetes, location of vessel occlusion, baseline National Institute of Health stroke scale score, stroke etiology, and plan for endovascular treatment. Design: EXIT-BT2 is a prospective, randomized, open-label, blinded assessment of endpoint (PROBE), and multi-center study. Eligible AIS patients between 4.5 and 6 h of onset are randomly assigned 1:1 into a TNK group or control group. The TNK group will receive TNK (0.25 mg/kg, a single bolus over 5–10 s, maximum 25 mg). The control group will receive standard medical care in compliance with national guidelines for acute ischemic stroke. Both groups will receive standard stroke care from randomization to 90 days after stroke onset according to national guidelines. Outcome: The primary efficacy endpoint is excellent functional outcome, defined as a modified Rankin Scale score 0–1 at 90 days after randomization, while the primary safety endpoint is symptomatic intracerebral hemorrhage, defined as National Institutes of Health Stroke Scale score increase ⩾4 caused by intracranial hemorrhage within 24 (−6/+12) h after randomization. Conclusions: The results of EXIT-BT2 may determine whether intravenous TNK has a favorable risk/benefit profile in AIS between 4.5 and 6 h of onset.