Abstract DP347: LYS241: A Novel Humanized Antibody Counteracting tPA-Mediated Neurotoxicity and BBB Disruption in Stroke

Introduction/Aims: Tissue plasminogen activator (tPA), though profibrinolytic, worsens ischemic brain injury by overactivating NMDA receptors (NMDAr), leading to excitotoxicity, disruption of tight junctions, and compromise of the blood-brain barrier (BBB). LYS241 is a first-in-class, humanized, and optimized monoclonal antibody derived from the original murine antibody glunomab. It selectively inhibits the pathological interaction between tPA and NMDAr without impairing the receptors’ normal physiological function . Methods: The binding affinity of LYS241 was evaluated using ELISA and competition assays , and further validated by immunostaining . Its therapeutic efficacy was comprehensively assessed in vivo in models of NMDA-induced excitotoxicity and thromboembolic stroke (middle cerebral artery occlusion, MCAo). LYS241 was administered both as a monotherapy and in combination with alteplase (rtPA) or tenecteplase (TNK), within either an acute or extended therapeutic window following stroke. Key outcomes—including lesion volume, functional recovery, and vascular recanalization—were measured using 7T MRI, laser speckle contrast imaging, and behavioral testing. Results: LYS241 demonstrated a superior binding affinity to NMDAr compared to glunomab. Our findings support the efficacy of LYS241 in reducing excitotoxicity and the resulting rtPA/TNK-induced neuronal cell death (n=8 animals per group). In the MCAo model, a single administration of LYS241—either within or beyond the therapeutic window of rtPA/TNK—significantly reduced lesion volume, enhanced recanalization, and led to improved functional outcomes , whether administered alone or in combination with thrombolysis (n=15-31 animals per group). Conclusions: In conclusion, by neutralizing excitotoxicity and blood-brain barrier disruption triggered by both endogenous tPA (overexpressed by endothelial cells and neurons after stroke) and exogenous tPA (alteplase and tenecteplase), LYS241 demonstrates strong therapeutic efficacy across both early and extended treatment windows. These findings highlight its potential as a standalone therapy or in combination with thrombolysis and/or thrombectomy . LYS241 is currently progressing through IND/CTA-enabling studies in preparation for a first-in-human clinical trial.