The blood-brain barrier (BBB) is af ormidable physical and enzymatic barrier that tightly controls the passage of molecules from the blood to the brain. In fact, less than 2% of all potential neurotherapeutics are able to cross it. Here,by applying the retro-enantio approach to ap eptide that targets the transferrin receptor,afull protease-resistant peptide with the capacity to act as aB BB shuttle was obtained and thus enabled the transport of av ariety of cargos into the central nervous system.