Abstract WP352: TNK-versus-tPA Thrombolysis in Experimental Ischemic Stroke under Acute Hyperglycemia

Introduction: Thrombolysis remains a critical element for acute ischemic stroke therapy. TNK (Tenecteplase) is a tPA mutant variant with practical and pharmacological advantages to tPA (Alteplase), but their risks and benefits in acute hyperglycemia-compounded stroke are still uncertain. It is also unclear whether higher doses of TNK (i.e. higher the currently FAD-approved dose of 0.25 mg/kg) increase the risk of intracerebral hemorrhage under hyperglycemia. Hypothesis: We hypothesized that a higher dose of TNK (4 mg/kg in mice, similar to 0.4 mg/kg in human) is more effective than tPA to minimize infarction and reduce hemorrhagic transformation in ischemic stroke with acute hyperglycemia due to its greater fibrin-associated activity and resistance to plasminogen activator inhibitor 1 (PAI1). Methods: Using a thrombin-enhanced photothrombotic stroke model (PMID32227212), we compared the effects of tPA (10 mg/kg) and TNK (2.5 and 4 mg/kg) in adult male C57BL/6 mice. We compared (a) therapeutic window under normoglycemia; (b) efficacy under acute hyperglycemia; (c) the incidence of hemorrhagic transformation and the extent of Evans Blue dye extravasation. We also explored the effectors of tPA-induced hemorrhagic transformation under acute hyperglycemia-compounded ischemic stroke. Results: Based on TTC-staining of the infarct size, the therapeutic window of tPA is around 4 h post-stroke, whereas 4 mg/kg TNK (but not the clinically equivalent dose at 2.5 mg/kg) extends the therapeutic window to 6 h post-stroke. When confounded by acute hyperglycemia, tPA treatment (administered at 2 h post-stroke) failed to reduce the infarct size (Fig 1A), but rather provoked cerebral hemorrhage and extravasation of intravenously injected Evans Blue dye (Fig 1B). In contrast, 4 mg/kg TNK, and to a lesser degree 2.5 mg/kg TNK, avoided hemorrhagic transformation and attenuated the extravasation of Evans Blue dye (Fig 1B). Moreover, acute hyperglycemia induced the tPA/PAI1 complex coated along the vascular endothelium after ischemia in ipsilateral cerebral cortex, which may account for the reduced tPA-thrombolysis efficacy. Conclusion: TNK at an optimal dose is a more potent and safer thrombolytic agent, particularly in acute hyperglycemia-confounded stroke. The mechanisms of acute hyperglycemia-enhanced tPA-hemorrhagic transformation remain to be investigated.