 BACKGROUND: Alteplase dissolves blood vessel clots in acute ischemic stroke and is the only approved acute drug treatment 412 hours of stroke onset. The overall benefit from alteplase is substantial, but up to 23 of patients with large artery clots may not achieve reopening of the vessel and up to 40 of the patients may remain severely disabled or die, leaving substantial room for improvement. Tenecteplase, widely used in coronary heart disease, may be more effective and may have less bleeding complications than alteplase, and may be the drug of choice also in stroke. 