Platelet-targeted thrombolysis for treatment of acute ischemic stroke.

Thrombolysis with tissue-type plasminogen activator (tPA) is still the main treatment for acute ischemic stroke. Nevertheless, tPA intervention is limited by a short therapeutic window, low recanalization rates and a risk of intracranial haemorrhage (ICH), raising a clinical demand for improved thrombolytic drugs. We examined a novel thrombolytic agent termed 'SCE5-scuPA', comprising a single-chain urokinase plasminogen activator (scuPA) fused with a single-chain antibody (SCE5) that targets the activated GPIIb/IIIa platelet receptor, for its effects in experimental stroke. SCE5-scuPA was first tested in whole blood clot degradation assay to demonstrate the benefit of platelet-targeted thrombolysis. The tail bleeding time, blood clearance and biodistribution were then determined to inform the use of SCE5-scuPA in mouse models of photothrombotic stroke and Middle Cerebral Artery occlusion (MCAo) against tenecteplase (TNK-tPA). The impacts of SCE5-scuPA on motor function, ICH, blood-brain barrier (BBB) integrity and immunosuppression were evaluated. Infarct size was measured by Computed Tomography and Magnetic Resonance Imaging. SCE5-scuPA enhanced clot degradation ex vivo compared to its non-platelet-targeting control. The maximal SCE5-scuPA dose that maintained hemostasis and a rapid blood clearance were determined. SCE5-scuPA administration both prior and 2h after photothrombotic stroke reduced the infarct volume. SCE5-scuPA also improved neurological deficit, decreased intracerebral blood deposits, preserved the BBB and alleviated immunosuppression post-stroke. In MCAo, SCE5-scuPA did not worsen stroke outcomes or caused ICH, and protected the BBB. Our findings support the ongoing development of platelet-targeted thrombolysis with SCE5-scuPA as a novel emergency treatment for AIS with a promising safety profile.