Blood-Brain Barrier Therapeutics for Neurological Diseases

The Blood-Brain Barrier (BBB) is a highly selective filter responsible for allowing certain gases such as oxygen and lipid-soluble molecules to pass (Anand 2014). Its selectiveness makes it challenging for many therapeutics to combat Alzheimer’s and Parkinson’s disease with external drug therapies. Large-molecule drug therapies never pass the BBB while small-molecule drugs pass only about 5% of the time (Pardridge 2005). In Alzheimer’s disease, tight junctions between endothelial cells degrade, causing an unregulated accumulation of amyloid-β (Aβ) protein (Ramanathan 2015). Consequently, this leads to the formation of neurofibrillary tangles that cut off the nutrient supply to the brain cells and kill neurons (Ramanathan 2015). In Parkinson’s disease, astrocyte mutations cause a build-up of α-synuclein (αSyn) which affects the neuroinflammatory response and causes dysfunction in dopaminergic neurons (Booth 2017; Meade 2019). New drug therapies for Alzheimer’s and Parkinson’s continue to undergo trials; some such as FPS-ZM1 and tilavonemab for Alzheimer’s and Ravicti for Parkinson’s have shown promising results. In addition, similarities in dysfunction for both diseases and some types of cancer have sparked possibilities in retargeting cancer drugs to improve Alzheimer's and Parkinson’s pathologies. This review will summarize current therapeutic advancements for Alzheimer’s and Parkinson’s disease and their possible future contributions.