Abstract WP338: Extracellular Vesicle -based therapeutic for Acute Ischemic Stroke AB126 functions via the CCR2/CCL2 Cell Signaling Pathway

Introduction: Following ischemic injury, cytokine release recruits immune cells to the site of damage, leading to neuroinflammation that exacerbates tissue injury and contributes to lasting deficits. The chemokine CCL2 (monocyte chemoattractant protein-1, MCP-1) plays a key role in recruiting monocytes and macrophages, making it an attractive target to prevent excessive post-stroke inflammation. AB126 is an investigational neural small extracellular vesicle (sEV) with robust neuroprotective and anti-inflammatory properties and recently gained FDA Investigational New Drug (IND) clearance to enter clinical trials for acute ischemic stroke (AIS). Here, we evaluate AB126, for its ability to mitigate neuroinflammation by targeting the CCL2 pathway. Methods: Neural stem cell culture media underwent tangential flow filtration and chromatography to separate and concentrate the sEV in AB126, followed by nanoparticle tracking analysis. AB126 was examined for the presence of the CCL2 receptor, CCR2, and evaluated for its ability to bind CCL2, effect levels of CCL2 in microglial cultures stimulated with lipopolysaccharide (LPS) or oxygen-glucose depravation (OGD) stress. Results: AB126 expresses the receptor CCR2 on the surface of approximately 58% of sEVs and demonstrates a half maximal inhibitory concentration (IC 50 ) of 3.85E+10 particles/mL in vitro for human CCL2. Similar results were obtained using rat CCL2, indicating AB126 is effective at binding CCL2 in both species. These results are confirmed by the reduction of secreted CCL2 by cell cultures in response to LPS insult or OGD stress. Conclusion: Based on numerous preclinical studies in mice, rats and pig using transcient and permanent MCAO models, AB126 is a viable treatment of AIS and has a cleared IND for AIS. These studies suggest that AB126 functions, at least partially, by the inhibition of the CCL2 signaling pathway and reducing neuroinflammation.