Repurposing antidiabetics for Alzheimer's disease and related neurodegenerative disorders: Translational challenges and role of nanoparticle-mediated CNS targeting.

Diabetes mellitus has been linked to cognitive impairment and Alzheimer's disease (AD). They share common pathologic pathways, including insulin resistance, mitochondrial dysfunction, oxidative stress, and chronic neuroinflammation. These shared mechanisms have prompted interest in repurposing antidiabetic agents as promising therapies for neurodegenerative diseases. Despite this overlap, these drugs face translational challenges, primarily due to their poor penetration across the blood-brain barrier (BBB) and, consequently, poor central nervous system (CNS) bioavailability. Nanoparticle-based drug delivery offers an alternative route to improve targeting of the CNS by increasing the drug stability and augmenting transport across the BBB. Although preclinical evidence showed promising results, the extent to which these findings translate into clinically tangible outcomes remains uncertain. This review critically evaluates the main preclinical studies on nanoparticle-mediated delivery of antidiabetic agents, with particular emphasis on AD and diabetes-associated cognitive impairment, where most available data are concentrated. We also discuss the main brain-targeting strategies, their limitations, and the translational challenges to their clinical application, particularly for conditions beyond AD, where the evidence remains sparse. Addressing these barriers is crucial for the development of nanomedicine-based approaches from bench to bedside. This review provides a critical standpoint on the field and highlights priorities for future research aimed at the effective translation of nanoparticle-enabled therapies for neurodegenerative diseases.