Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron loss, skeletal muscle atrophy, paralysis, and eventually death. Mitochondrial dysfunction plays a pivotal role in ALS pathogenesis, although the precise pathogenic mechanisms remain elusive, and effective therapeutic strategies are extremely limited. In this study, we developed a small-molecule inhibitor, UA-30, which directly targets RalA, and explored its potential for the treatment of ALS. We found that when administered via oral gavage for 6 weeks following the onset of motor deficit, UA-30 extended lifespan and improved motor function of SOD1G93A mice, a model of ALS. UA-30 ameliorated motor neuron loss, neuroinflammation, fibrosis, and mitochondrial dysfunction, as evidenced by energy recovery, decreased oxidative stress, and enhanced mitophagy. Mechanistically, UA-30 inhibited RalA activity and thereby modulated ERK/FOXO3a signaling, which inhibited FOXO3a degradation via the ubiquitin-proteasome pathway; enhanced FOXO3a stability; and upregulated the expression of mitophagy-related genes in this ALS mouse model. The beneficial effects of UA-30 in ALS were abolished by overexpression of the constitutively active form of RalA (RalAG23V) or Mdivi-1 treatment. These findings support RalA inhibition as a therapeutic strategy for enhancing mitophagy and mitigating ALS-like pathology and support UA-30 as an orally active candidate for further preclinical development.
