Discovery and preclinical validation of a translationally optimized mitochondrial complex I modulator for Alzheimer's disease.

Alzheimer's disease (AD) is characterized by progressive metabolic failure, impaired mitochondrial function, and diminished adaptive stress responses, highlighting the need for disease-modifying therapies that restore cellular resilience rather than target downstream pathology. Here, we report the discovery and preclinical validation of C273, a translationally optimized, brain-penetrant mitochondrial complex I (mtCI) modulator developed through medicinal chemistry optimization of our first-generation compounds. C273 retained nanomolar neuroprotective activity against Aβ-induced toxicity while exhibiting favorable drug-like properties, including high oral bioavailability, efficient brain penetration, microsomal stability, minimal CYP and off-target pharmacology liabilities, and selective mild modulation of mtCI. Mechanistic studies demonstrated that C273 activated AMP-activated protein kinase (AMPK) and coordinated antioxidant, autophagic, anti-inflammatory, and mitochondrial quality-control pathways in cultured cells and mouse brain. These responses were absent in AMPKα1/α2-deficient cells, establishing AMPK as an essential mediator, while rotenone pretreatment abolished C273-mediated neuroprotection, supporting engagement of the mtCI quinone-binding site. Repeated administration to wild-type mice for 30 days produced no detectable cardiac or hepatic toxicity. Importantly, C273 activated the same neuroprotective pathways and reduced Aβ and p-Tau levels in induced pluripotent stem cell-derived cerebral organoids from patients with sporadic AD. Together, these findings establish mild modulation of mtCI as a therapeutic strategy to restore metabolic resilience and identify C273 as a promising disease-modifying candidate for AD treatment.