The blood-brain barrier (BBB) is a layer of specialised cells lining the brain’s blood vessels that protects the brain and maintains its homeostasis by tightly regulating the exchange of molecules between the blood and brain. The BBB also blocks >98% of drugs and therapeutic leads, representing a major challenge for drug development.[1,2]
Various brain delivery strategies have been proposed, yet most fail to meet expectations. One approach relies on peptides able to cross the BBB as shuttles for drug cargoes.[1-3] Examples of such BBB-crossing peptides include apamin from bee venom and chlorotoxin from scorpion venom, with studies demonstrating their ability to shuttle cargo molecules across the BBB[3]. We hypothesise that these are just the tip of the iceberg, and that animal venoms are a rich but underexplored natural source of peptides that have evolved over millions of years to refine their ability to reach targets in the brain.
To address this, we optimised a platform for the systematic screening of peptides based on their BBB permeability. We combined a human BBB Transwell cell model (hCMEC/D3)[4,5] with a mass spectrometry (MS) approach for peptide identification and quantification. Our MS-based workflow simultaneously supports rapid screening and implementation into a venom discovery pipeline, where MS is also crucial for identifying and sequencing lead compounds from complex mixtures such as venom fractions. We first validated our platform by assessing a range of human neuropeptides and known BBB-crossing peptides, identifying positive (e.g., insulin) and negative (e.g., neurotensin) controls and establishing permeability benchmarks that are fundamental for evaluating new compounds. Using this approach, we have identified a venom peptide that efficiently crosses the BBB and can improve the delivery of neurotensin – a therapeutically relevant neuropeptide whose development as a drug is hampered by poor BBB crossing.
As a whole, our approach enables a first-of-its-kind systematic exploration of animal venoms, accelerating the discovery of BBB-crossing peptides. We expect our work to provide new insights and data characterising the ability of venom peptides to cross the BBB, and to identify new lead molecules that can be optimised into novel, non-toxic and efficient brain shuttles, supporting better drug development for brain diseases.