 Acute stroke is the third leading cause of mortality in developed countries and the major medical cause of disability in adults. The outcome can be improved by early treatment with thrombolysis. Alteplase r-tPA is the only approved thrombolytic drug in the indication of acute ischemic stroke. However, the use of alteplase is currently restricted by the need to administer it within 3 hours of symptom onset. As the risk of transforming a cerebral infarct into haemorrhage probably rises as the time elapsed increases, a thrombolytic drug that carries a lower risk of haemorrhage than alteplase may offer a wider time-to-treatment window and improve the safety profile. 