Large Artery occlusion Treated in Extended Time with Mechanical Thrombectomy (LATE-MT): protocol for a multicenter randomized clinical trial

Background: High-quality randomized controlled trials (RCTs) have extended the endovascular therapy (EVT) time window to 24 hours post-stroke onset in selected patients with acute ischemic stroke (AIS). Recent retrospective studies indicate that EVT performed beyond 24 hours may still improve clinical outcomes. However, the specific benefit-risk profile in this ultra-late window remains unclear. Aim: The trial is designed to address this evidence gap and determine the benefit-risk balance of EVT in the ultra-late window. Methods and design: The Large Artery occlusion Treated in Extended Time with Mechanical Thrombectomy (LATE-MT) is an investigator-initiated, multicenter, prospective, randomized, open, blinded-endpoint assessment (PROBE) clinical trial. The trial adopted an adaptive group-sequential design, recruiting 336 AIS patients with large-vessel occlusion within 24 to 72 hours of the last known well across 35 stroke centers in China. Eligible subjects who meet both clinical and imaging selection criteria are randomized 1:1 to EVT or medical management. Outcomes: The primary outcome is an ordinal shift analysis of scores on the modified Rankin scale (mRS) at 90 days. Key secondary outcomes include neurological function at 24 hours and 7 days, death/major disability and utility-weighted mRS (UW-mRS) at 90 days. Safety outcomes include any intracranial hemorrhage (ICH), symptomatic ICH, serious adverse event, and all procedural complications.