The central nervous system (CNS), which includes the brain, is endowed with a unique vascular system compared to other tissues and organs. It restricts very effectively the passage of toxic molecules and infectious agents from the blood to the nervous tissue and is known as the "blood-brain barrier” (BBB). The BBB represents a large surface of potential exchange between the blood and nervous tissue, however, because of its specific properties, the BBB is also a major obstacle to the use of drugs to treat CNS disorders. An estimated 98% of all active drugs and virtually all biomolecules developed by the biopharmaceutical industry, including peptides, proteins and therapeutic antibodies, do not cross the BBB. The BBB thus represents a real technological barrier for delivery to the brain of imaging agents and drugs developed to treat serious brain diseases (neurodegenerative diseases-NDDs- including Alzheimer’s disease, brain tumours, etc.). Membranes of various cell types in different organs and diseased tissues such as tumours can also be difficult to cross for efficient drug delivery. The scientific approach of VECT-HORUS is based on the principle that complex biological barriers, the first of which the BBB, are not only physical barriers, but also functional barriers whose natural transport mechanisms may be advantageously used to deliver drugs or imaging agents into their target territory: specific cell type, organ, brain, tumour.