Olfactory targeting through intranasal delivery of biopharmaceutical drugs to the brain: current development.

Many therapeutic drugs are difficult to reach the central nervous system (CNS) from the systemic blood circulation because the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) form a very effective barrier which prevents most molecules from passing through. To bypass BBB, drugs can be delivered through olfactory region for nose-to-brain targeting. Peptide and protein drugs have been developed for the treatment of various neurodegenerative diseases. Drug delivery of these therapeutic proteins is facing several challenges because of the instability, high enzymatic metabolism, low gastrointestinal absorption, rapid renal elimination, and potential immunogenicity. New genetically engineered biotechnology products, such as recombinant human nerve growth factor, human VEGF, and interferons, are now possible to be delivered into the brain from the non-invasive intranasal route. For gene therapy, intranasal route is also a promising alternative method to deliver plasmid DNA to the brain. This review provides an overview of strategies to improve the drug delivery to the brain and the latest development of protein, peptide, and gene intranasal delivery for brain targeting.