Intranasal drug delivery to the brain for neurodegenerative diseases: Current efforts and challenges in delivery platforms and modeling.

Neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD), globally pose a significant challenge with an aging population. Despite the presence of various therapeutic agents, AD and PD treatments with small molecules currently only address the symptoms; certain biologic agents for AD have been approved for their disease-modifying effects, but the risk of intracerebral hemorrhage severely limits their use. Moreover, the bioavailability of orally administered agents in the brain is challenged by the blood-brain barrier, complicating brain-targeted drug development. Extensive efforts are currently underway to develop intranasal platforms with nanoparticles for direct nose-to-brain drug delivery. Additionally, various in vitro designs involving brain organoids, and in vivo models, such as rodents and zebrafish, have been explored to improve the efficiency and accuracy of preclinical models. Efforts to develop sophisticated computational modeling of intranasal drug delivery, including computational fluid dynamics (CFD) deposition and physiologically based pharmacokinetics (PBPK) modeling, also continue to advance the intranasal drug delivery research and potentially improve the feasibility of developing clinically relevant intranasal platforms for neurodegenerative disease.