EPI-589, a redox-active neuroprotectant, potently protects cultured cells from oxidative stress and alleviates symptomatic and pathological progression of motor neuron disease in the wobbler mouse

Oxidative stress is believed to play a significant role in the pathophysiology of amyotrophic lateral sclerosis (ALS), the most common form of motor neuron disease. The present study aims to firstly investigate the antioxidant activities of EPI-589, a small-molecule quinone derivative, under cell-free or cell culture conditions, and explore the in vivo efficacy of EPI-589 in the wobbler mouse model of human motor neuron disease. The reduced form of EPI-589 showed hydroxyl radical scavenging activities, whereas the oxidized form i.e. EPI-589 did not. In cellular models utilizing ALS patient-derived fibroblasts carrying mutations in the fused in sarcoma (FUS) gene or superoxide dismutase 1 (SOD1) gene, EPI-589 potently protected cells from oxidative stress induced by buthionine sulfoximine and ferric citrate. Protective effect of EPI-589 was also observed in culture of mouse immortalized striatal STHdHQ7/Q7 cells with cystine deprivation. In wobbler mice, oral administration of dietary EPI-589 provided long-lasting amelioration of both of deterioration of the rotarod walking performance and progression of forelimb deformity in wobbler mice throughout the treatment. In separate studies, we found that EPI-589 significantly suppressed changes of pathophysiological markers such as plasma phosphorylated neurofilament heavy chain, urinary 8-hydroxy-2'-deoxyguanosine, and cervical N-acetylaspartate in untreated wobbler mice. Thus, the present study firstly demonstrates that EPI-589 is a highly potent, redox-active neuroprotectant and robustly delays the symptomatic and pathophysiological progression of motor neuron disease in the wobbler mouse, and these findings strongly encourage further exploration of the therapeutic potential of EPI-589 for the treatment of ALS. ### Competing Interest Statement All authors are employees of Sumitomo Dainippon Pharma Co., Ltd. There is no other conflict of interest to report.