Abstract A069: A Novel Therapeutic Approach to Improve Motor Dysfunction in a Non-Human Primate Chronic Ischemic Stroke Model Using mRNA-Lipid Nanoparticles Treatment

Introduction: Many patients who survive an ischemic stroke experience long-term motor dysfunction, resulting in reduced quality of life. Despite advancements in rehabilitation and treatments, there is still a significant unmet need for effective treatments to address long-term motor dysfunction in ischemic stroke. We investigated a novel treatment strategy using a therapeutic mRNA to induce neural regeneration. Methods: ASP2246 is an investigational drug candidate comprised of mRNA encoding a transcription factor for neural regeneration (NeuroD1) encapsulated in lipid nanoparticles (mRNA-LNP) . We tested the ability of ASP2246 to convert astrocytes to neurons in U-251 human astrocytoma cell line. Moreover, we established a cynomolgus monkey stroke model with long-term motor dysfunction by injecting endothelin-1 into the basal ganglia region, around the internal capsule. To evaluate the efficacy of A2246, we used the modified Rankin Scale for cynomolgus monkey (Cyno.mRS) and the Non-Human Primate Stroke Scale (NHPSS) to assess motor function severity. We conducted a randomized, blinded efficacy study, with monkeys receiving either ASP2246 (2 dose levels) or saline (n=6-7 each) once via stereotaxic injection into the stroke site three weeks post-stroke. Behavior was assessed for 13 weeks after administration. Results: In vitro, ASP2246 showed transient expression of NeuroD1 followed by conversions from astrocytes to neurons, indicated by neuronal markers and neuron-like morphology. In the newly established monkey stroke model, motor dysfunction persisted for over three months without any treatment or rehabilitation. In the randomized, blinded NHP study, ASP2246 significantly reduced both Cyno.mRS and NHPSS scores at 13 weeks. The median Cyno.mRS scores for the control, low-dose, and high-dose ASP2246 groups were 4, 3 and 1, respectively, with significant improvement noted in the high-dose group compared to the saline control (p<0.05). No ASP2246-related abnormalities were observed in clinical signs, food consumption, or body weight during the study period. Conclusions: ASP2246, a novel mRNA-LNP drug, was able to convert astrocytes into neurons in a cell culture model and improved motor dysfunction in a chronic ischemic stroke cynomolgus monkey model. There were no ASP2246-related adverse findings.